From 867a8cf108ff60028a303e92af3f95a937f4710c Mon Sep 17 00:00:00 2001
From: Artem Bilan <abilan@pivotal.io>
Date: Fri, 7 Feb 2020 13:40:39 -0500
Subject: [PATCH] GH-3155: Add support for Java DSL extensions (#3167)

* GH-3155: Add support for Java DSL extensions

Fixes https://github.com/spring-projects/spring-integration/issues/3155

Provide an `IntegrationFlowExtension` for possible custom EI-operators
in the target project use-cases.

* * Move `IntegrationFlowExtension` tests ot its own test class
* Make all the `IntegrationComponentSpec` ctors as `protected` for possible custom extensions
* Make some `BaseIntegrationFlowDefinition` methods and properties as `protected` to get them
access from the `IntegrationFlowExtension` implementations
* Document the feature

* * Fix language and typos in docs

* * Add `protected` to one more `GatewayEndpointSpec` ctor
* Add JavaDocs to `GatewayEndpointSpec` methods

* * Add `protected` to one more `JmsPollableMessageChannelSpec` ctor
---
 .../integration/dsl/AbstractRouterSpec.java   |   6 +-
 .../integration/dsl/AggregatorSpec.java       |   4 +-
 .../integration/dsl/BarrierSpec.java          |   4 +-
 .../dsl/BaseIntegrationFlowDefinition.java    |  67 +++++-----
 .../integration/dsl/DelayerEndpointSpec.java  |   6 +-
 .../integration/dsl/DirectChannelSpec.java    |   5 +-
 .../integration/dsl/EnricherSpec.java         |   8 +-
 .../integration/dsl/ExecutorChannelSpec.java  |   4 +-
 .../integration/dsl/FilterEndpointSpec.java   |   6 +-
 .../dsl/FluxMessageChannelSpec.java           |   4 +-
 .../integration/dsl/GatewayEndpointSpec.java  |  38 +++++-
 .../integration/dsl/GatewayProxySpec.java     |  14 +--
 .../integration/dsl/GenericEndpointSpec.java  |   6 +-
 .../integration/dsl/HeaderEnricherSpec.java   |   8 +-
 .../dsl/IntegrationFlowExtension.java         |  98 +++++++++++++++
 .../integration/dsl/PriorityChannelSpec.java  |   4 +-
 .../integration/dsl/PublishSubscribeSpec.java |   6 +-
 .../integration/dsl/QueueChannelSpec.java     |  10 +-
 .../dsl/RecipientListRouterSpec.java          |   4 +-
 .../dsl/RendezvousChannelSpec.java            |   4 +-
 .../integration/dsl/ResequencerSpec.java      |   4 +-
 .../integration/dsl/RouterSpec.java           |   4 +-
 .../integration/dsl/ScatterGatherSpec.java    |   4 +-
 .../dsl/SourcePollingChannelAdapterSpec.java  |   6 +-
 .../integration/dsl/SplitterEndpointSpec.java |   6 +-
 .../IntegrationFlowExtensionTests.java        | 117 ++++++++++++++++++
 .../feed/dsl/FeedEntryMessageSourceSpec.java  |   6 +-
 .../dsl/FileInboundChannelAdapterSpec.java    |   8 +-
 .../file/dsl/FileSplitterSpec.java            |   8 +-
 .../dsl/FileWritingMessageHandlerSpec.java    |  10 +-
 .../integration/file/dsl/TailAdapterSpec.java |   6 +-
 .../ftp/dsl/FtpInboundChannelAdapterSpec.java |   4 +-
 .../ftp/dsl/FtpMessageHandlerSpec.java        |   8 +-
 .../ftp/dsl/FtpOutboundGatewaySpec.java       |   4 +-
 ...FtpStreamingInboundChannelAdapterSpec.java |  11 +-
 .../http/dsl/BaseHttpInboundEndpointSpec.java |   4 +-
 .../http/dsl/HttpControllerEndpointSpec.java  |   4 +-
 .../http/dsl/HttpMessageHandlerSpec.java      |   8 +-
 .../dsl/HttpRequestHandlerEndpointSpec.java   |   4 +-
 .../ip/dsl/AbstractConnectionFactorySpec.java |   7 +-
 ...AbstractUdpOutboundChannelAdapterSpec.java |   7 +-
 .../dsl/TcpClientConnectionFactorySpec.java   |   8 +-
 .../ip/dsl/TcpInboundChannelAdapterSpec.java  |   8 +-
 .../ip/dsl/TcpInboundGatewaySpec.java         |   8 +-
 .../ip/dsl/TcpOutboundChannelAdapterSpec.java |   8 +-
 .../ip/dsl/TcpOutboundGatewaySpec.java        |   4 +-
 .../dsl/TcpServerConnectionFactorySpec.java   |   8 +-
 .../ip/dsl/UdpInboundChannelAdapterSpec.java  |   7 +-
 ...dpMulticastOutboundChannelAdapterSpec.java |  10 +-
 .../UdpUnicastOutboundChannelAdapterSpec.java |  10 +-
 .../dsl/JmsDefaultListenerContainerSpec.java  |   4 +-
 .../jms/dsl/JmsDestinationAccessorSpec.java   |   4 +-
 .../jms/dsl/JmsInboundChannelAdapterSpec.java |   6 +-
 .../jms/dsl/JmsInboundGatewaySpec.java        |   6 +-
 .../jms/dsl/JmsListenerContainerSpec.java     |   4 +-
 .../jms/dsl/JmsMessageChannelSpec.java        |   4 +-
 .../JmsMessageDrivenChannelAdapterSpec.java   |   6 +-
 .../dsl/JmsOutboundChannelAdapterSpec.java    |   6 +-
 .../jms/dsl/JmsOutboundGatewaySpec.java       |   4 +-
 .../dsl/JmsPollableMessageChannelSpec.java    |  15 +--
 ...JmsPublishSubscribeMessageChannelSpec.java |   4 +-
 .../integration/jms/dsl/JmsTemplateSpec.java  |   4 +-
 .../jpa/dsl/JpaInboundChannelAdapterSpec.java |   6 +-
 .../dsl/JpaRetrievingOutboundGatewaySpec.java |   4 +-
 .../dsl/JpaUpdatingOutboundEndpointSpec.java  |   6 +-
 .../mail/dsl/ImapIdleChannelAdapterSpec.java  |  10 +-
 .../ImapMailInboundChannelAdapterSpec.java    |   6 +-
 .../dsl/MailSendingMessageHandlerSpec.java    |   6 +-
 .../Pop3MailInboundChannelAdapterSpec.java    |  12 +-
 .../dsl/MongoDbOutboundGatewaySpec.java       |   4 +-
 .../ReactiveMongoDbMessageHandlerSpec.java    |   6 +-
 .../dsl/ReactiveMongoDbMessageSourceSpec.java |   7 +-
 .../dsl/RSocketInboundGatewaySpec.java        |   4 +-
 .../dsl/RSocketOutboundGatewaySpec.java       |   4 +-
 .../dsl/SftpInboundChannelAdapterSpec.java    |   6 +-
 .../sftp/dsl/SftpMessageHandlerSpec.java      |  14 ++-
 .../sftp/dsl/SftpOutboundGatewaySpec.java     |   5 +-
 ...ftpStreamingInboundChannelAdapterSpec.java |   7 +-
 .../dsl/WebFluxInboundEndpointSpec.java       |   4 +-
 .../dsl/WebFluxMessageHandlerSpec.java        |  10 +-
 src/reference/asciidoc/dsl.adoc               |  60 +++++++++
 src/reference/asciidoc/whats-new.adoc         |  17 ++-
 82 files changed, 607 insertions(+), 275 deletions(-)
 create mode 100644 spring-integration-core/src/main/java/org/springframework/integration/dsl/IntegrationFlowExtension.java
 create mode 100644 spring-integration-core/src/test/java/org/springframework/integration/dsl/extensions/IntegrationFlowExtensionTests.java

diff --git a/spring-integration-core/src/main/java/org/springframework/integration/dsl/AbstractRouterSpec.java b/spring-integration-core/src/main/java/org/springframework/integration/dsl/AbstractRouterSpec.java
index 44f7b9e857..f3919440ec 100644
--- a/spring-integration-core/src/main/java/org/springframework/integration/dsl/AbstractRouterSpec.java
+++ b/spring-integration-core/src/main/java/org/springframework/integration/dsl/AbstractRouterSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -34,7 +34,7 @@ public class AbstractRouterSpec<S extends AbstractRouterSpec<S, R>, R extends Ab
 
 	private boolean defaultToParentFlow;
 
-	AbstractRouterSpec(R router) {
+	protected AbstractRouterSpec(R router) {
 		super(router);
 	}
 
@@ -100,7 +100,7 @@ public class AbstractRouterSpec<S extends AbstractRouterSpec<S, R>, R extends Ab
 		return _this();
 	}
 
-	boolean isDefaultToParentFlow() {
+	protected boolean isDefaultToParentFlow() {
 		return this.defaultToParentFlow;
 	}
 
diff --git a/spring-integration-core/src/main/java/org/springframework/integration/dsl/AggregatorSpec.java b/spring-integration-core/src/main/java/org/springframework/integration/dsl/AggregatorSpec.java
index 1de4d3c2de..fb8c3a831c 100644
--- a/spring-integration-core/src/main/java/org/springframework/integration/dsl/AggregatorSpec.java
+++ b/spring-integration-core/src/main/java/org/springframework/integration/dsl/AggregatorSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -39,7 +39,7 @@ public class AggregatorSpec extends CorrelationHandlerSpec<AggregatorSpec, Aggre
 
 	private Function<MessageGroup, Map<String, Object>> headersFunction;
 
-	AggregatorSpec() {
+	protected AggregatorSpec() {
 		super(new AggregatingMessageHandler(new DefaultAggregatingMessageGroupProcessor()));
 	}
 
diff --git a/spring-integration-core/src/main/java/org/springframework/integration/dsl/BarrierSpec.java b/spring-integration-core/src/main/java/org/springframework/integration/dsl/BarrierSpec.java
index 0c76e81b86..769617d723 100644
--- a/spring-integration-core/src/main/java/org/springframework/integration/dsl/BarrierSpec.java
+++ b/spring-integration-core/src/main/java/org/springframework/integration/dsl/BarrierSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -52,7 +52,7 @@ public class BarrierSpec extends ConsumerEndpointSpec<BarrierSpec, BarrierMessag
 
 	private boolean async;
 
-	BarrierSpec(long timeout) {
+	protected BarrierSpec(long timeout) {
 		super(null);
 		this.timeout = timeout;
 	}
diff --git a/spring-integration-core/src/main/java/org/springframework/integration/dsl/BaseIntegrationFlowDefinition.java b/spring-integration-core/src/main/java/org/springframework/integration/dsl/BaseIntegrationFlowDefinition.java
index 789c72faa1..2a1f643058 100644
--- a/spring-integration-core/src/main/java/org/springframework/integration/dsl/BaseIntegrationFlowDefinition.java
+++ b/spring-integration-core/src/main/java/org/springframework/integration/dsl/BaseIntegrationFlowDefinition.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2019 the original author or authors.
+ * Copyright 2019-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -121,10 +121,10 @@ public abstract class BaseIntegrationFlowDefinition<B extends BaseIntegrationFlo
 
 	private static final String MESSAGE_PROCESSOR_SPEC_MUST_NOT_BE_NULL = "'messageProcessorSpec' must not be null";
 
-	private static final SpelExpressionParser PARSER = new SpelExpressionParser();
-
 	private static final Set<MessageProducer> REFERENCED_REPLY_PRODUCERS = new HashSet<>();
 
+	protected static final SpelExpressionParser PARSER = new SpelExpressionParser(); //NOSONAR - final
+
 	protected final Map<Object, String> integrationComponents = new LinkedHashMap<>(); //NOSONAR - final
 
 	private MessageChannel currentMessageChannel;
@@ -380,7 +380,7 @@ public abstract class BaseIntegrationFlowDefinition<B extends BaseIntegrationFlo
 		return wireTap(wireTapChannel, wireTapConfigurer);
 	}
 
-	private MessageChannel obtainInputChannelFromFlow(IntegrationFlow flow) {
+	protected MessageChannel obtainInputChannelFromFlow(IntegrationFlow flow) {
 		Assert.notNull(flow, "'flow' must not be null");
 		MessageChannel messageChannel = flow.getInputChannel();
 		if (messageChannel == null) {
@@ -1222,6 +1222,18 @@ public abstract class BaseIntegrationFlowDefinition<B extends BaseIntegrationFlo
 		return enrichHeaders(headers.get(), endpointConfigurer);
 	}
 
+	/**
+	 * Accept a {@link Map} of values to be used for the
+	 * {@link Message} header enrichment.
+	 * {@code values} can apply an {@link Expression}
+	 * to be evaluated against a request {@link Message}.
+	 * @param headers the Map of headers to enrich.
+	 * @return the current {@link IntegrationFlowDefinition}.
+	 */
+	public B enrichHeaders(Map<String, Object> headers) {
+		return enrichHeaders(headers, null);
+	}
+
 	/**
 	 * Accept a {@link Map} of values to be used for the
 	 * {@link Message} header enrichment.
@@ -1908,7 +1920,7 @@ public abstract class BaseIntegrationFlowDefinition<B extends BaseIntegrationFlo
 		return route(new RouterSpec<>(new MethodInvokingRouter(processor)), routerConfigurer);
 	}
 
-	private <R extends AbstractMessageRouter, S extends AbstractRouterSpec<S, R>> B route(S routerSpec,
+	protected <R extends AbstractMessageRouter, S extends AbstractRouterSpec<? super S, R>> B route(S routerSpec,
 			Consumer<S> routerConfigurer) {
 
 		if (routerConfigurer != null) {
@@ -2825,6 +2837,17 @@ public abstract class BaseIntegrationFlowDefinition<B extends BaseIntegrationFlo
 				.addComponent(downstream);
 	}
 
+	/**
+	 * Add a {@value IntegrationContextUtils#NULL_CHANNEL_BEAN_NAME} bean into this flow
+	 * definition as a terminal operator.
+	 * @return The {@link IntegrationFlow} instance based on this definition.
+	 * @since 5.1
+	 */
+	public IntegrationFlow nullChannel() {
+		return channel(IntegrationContextUtils.NULL_CHANNEL_BEAN_NAME)
+				.get();
+	}
+
 	/**
 	 * Represent an Integration Flow as a Reactive Streams {@link Publisher} bean.
 	 * @param <T> the expected {@code payload} type
@@ -2858,19 +2881,7 @@ public abstract class BaseIntegrationFlowDefinition<B extends BaseIntegrationFlo
 		return new PublisherIntegrationFlow<>(components, publisher);
 	}
 
-	/**
-	 * Add a {@value IntegrationContextUtils#NULL_CHANNEL_BEAN_NAME} bean into this flow
-	 * definition as a terminal operator.
-	 * @return The {@link IntegrationFlow} instance based on this definition.
-	 * @since 5.1
-	 */
-	public IntegrationFlow nullChannel() {
-		return channel(IntegrationContextUtils.NULL_CHANNEL_BEAN_NAME)
-				.get();
-	}
-
-	@SuppressWarnings(UNCHECKED)
-	private <S extends ConsumerEndpointSpec<S, ? extends MessageHandler>> B register(S endpointSpec,
+	protected <S extends ConsumerEndpointSpec<? super S, ? extends MessageHandler>> B register(S endpointSpec,
 			Consumer<S> endpointConfigurer) {
 
 		if (endpointConfigurer != null) {
@@ -2906,7 +2917,7 @@ public abstract class BaseIntegrationFlowDefinition<B extends BaseIntegrationFlo
 		return addComponent(endpointSpec).currentComponent(factoryBeanTuple2.getT2());
 	}
 
-	private B registerOutputChannelIfCan(MessageChannel outputChannel) {
+	protected B registerOutputChannelIfCan(MessageChannel outputChannel) {
 		if (!(outputChannel instanceof FixedSubscriberChannelPrototype)) {
 			addComponent(outputChannel, null);
 			Object currComponent = getCurrentComponent();
@@ -2947,7 +2958,7 @@ public abstract class BaseIntegrationFlowDefinition<B extends BaseIntegrationFlo
 		return _this();
 	}
 
-	private boolean isOutputChannelRequired() {
+	protected boolean isOutputChannelRequired() {
 		Object currentElement = getCurrentComponent();
 		if (currentElement != null) {
 			if (AopUtils.isAopProxy(currentElement)) {
@@ -3006,7 +3017,7 @@ public abstract class BaseIntegrationFlowDefinition<B extends BaseIntegrationFlo
 		return this.integrationFlow;
 	}
 
-	private void checkReuse(MessageProducer replyHandler) {
+	protected void checkReuse(MessageProducer replyHandler) {
 		Assert.isTrue(!REFERENCED_REPLY_PRODUCERS.contains(replyHandler),
 				"A reply MessageProducer may only be referenced once ("
 						+ replyHandler
@@ -3014,19 +3025,7 @@ public abstract class BaseIntegrationFlowDefinition<B extends BaseIntegrationFlo
 		REFERENCED_REPLY_PRODUCERS.add(replyHandler);
 	}
 
-	/**
-	 * Accept a {@link Map} of values to be used for the
-	 * {@link Message} header enrichment.
-	 * {@code values} can apply an {@link Expression}
-	 * to be evaluated against a request {@link Message}.
-	 * @param headers the Map of headers to enrich.
-	 * @return the current {@link IntegrationFlowDefinition}.
-	 */
-	public B enrichHeaders(Map<String, Object> headers) {
-		return enrichHeaders(headers, null);
-	}
-
-	private static Object extractProxyTarget(Object target) {
+	protected static Object extractProxyTarget(Object target) {
 		if (!(target instanceof Advised)) {
 			return target;
 		}
diff --git a/spring-integration-core/src/main/java/org/springframework/integration/dsl/DelayerEndpointSpec.java b/spring-integration-core/src/main/java/org/springframework/integration/dsl/DelayerEndpointSpec.java
index 616e34ea38..7a27124b46 100644
--- a/spring-integration-core/src/main/java/org/springframework/integration/dsl/DelayerEndpointSpec.java
+++ b/spring-integration-core/src/main/java/org/springframework/integration/dsl/DelayerEndpointSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -42,11 +42,11 @@ import org.springframework.util.Assert;
  *
  * @since 5.0
  */
-public final class DelayerEndpointSpec extends ConsumerEndpointSpec<DelayerEndpointSpec, DelayHandler> {
+public class DelayerEndpointSpec extends ConsumerEndpointSpec<DelayerEndpointSpec, DelayHandler> {
 
 	private final List<Advice> delayedAdvice = new LinkedList<>();
 
-	DelayerEndpointSpec(DelayHandler delayHandler) {
+	protected DelayerEndpointSpec(DelayHandler delayHandler) {
 		super(delayHandler);
 		Assert.notNull(delayHandler, "'delayHandler' must not be null.");
 		this.handler.setDelayedAdviceChain(this.delayedAdvice);
diff --git a/spring-integration-core/src/main/java/org/springframework/integration/dsl/DirectChannelSpec.java b/spring-integration-core/src/main/java/org/springframework/integration/dsl/DirectChannelSpec.java
index 7c2fb599d1..74e956fe24 100644
--- a/spring-integration-core/src/main/java/org/springframework/integration/dsl/DirectChannelSpec.java
+++ b/spring-integration-core/src/main/java/org/springframework/integration/dsl/DirectChannelSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -37,7 +37,4 @@ public class DirectChannelSpec extends LoadBalancingChannelSpec<DirectChannelSpe
 		return super.doGet();
 	}
 
-	DirectChannelSpec() {
-	}
-
 }
diff --git a/spring-integration-core/src/main/java/org/springframework/integration/dsl/EnricherSpec.java b/spring-integration-core/src/main/java/org/springframework/integration/dsl/EnricherSpec.java
index 5645ea1d31..d26795ffa7 100644
--- a/spring-integration-core/src/main/java/org/springframework/integration/dsl/EnricherSpec.java
+++ b/spring-integration-core/src/main/java/org/springframework/integration/dsl/EnricherSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -47,11 +47,11 @@ import reactor.util.function.Tuple2;
  */
 public class EnricherSpec extends ConsumerEndpointSpec<EnricherSpec, ContentEnricher> {
 
-	private final Map<String, Expression> propertyExpressions = new HashMap<>();
+	protected final Map<String, Expression> propertyExpressions = new HashMap<>(); // NOSONAR - final
 
-	private final Map<String, HeaderValueMessageProcessor<?>> headerExpressions = new HashMap<>();
+	protected final Map<String, HeaderValueMessageProcessor<?>> headerExpressions = new HashMap<>(); // NOSONAR - final
 
-	EnricherSpec() {
+	protected EnricherSpec() {
 		super(new ContentEnricher());
 	}
 
diff --git a/spring-integration-core/src/main/java/org/springframework/integration/dsl/ExecutorChannelSpec.java b/spring-integration-core/src/main/java/org/springframework/integration/dsl/ExecutorChannelSpec.java
index 69eddf36db..d27a8fe08a 100644
--- a/spring-integration-core/src/main/java/org/springframework/integration/dsl/ExecutorChannelSpec.java
+++ b/spring-integration-core/src/main/java/org/springframework/integration/dsl/ExecutorChannelSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -29,7 +29,7 @@ public class ExecutorChannelSpec extends LoadBalancingChannelSpec<ExecutorChanne
 
 	private final Executor executor;
 
-	ExecutorChannelSpec(Executor executor) {
+	protected ExecutorChannelSpec(Executor executor) {
 		this.executor = executor;
 	}
 
diff --git a/spring-integration-core/src/main/java/org/springframework/integration/dsl/FilterEndpointSpec.java b/spring-integration-core/src/main/java/org/springframework/integration/dsl/FilterEndpointSpec.java
index 6b2e9f98f6..dc64fc2e3d 100644
--- a/spring-integration-core/src/main/java/org/springframework/integration/dsl/FilterEndpointSpec.java
+++ b/spring-integration-core/src/main/java/org/springframework/integration/dsl/FilterEndpointSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -26,9 +26,9 @@ import org.springframework.messaging.MessageChannel;
  *
  * @since 5.0
  */
-public final class FilterEndpointSpec extends ConsumerEndpointSpec<FilterEndpointSpec, MessageFilter> {
+public class FilterEndpointSpec extends ConsumerEndpointSpec<FilterEndpointSpec, MessageFilter> {
 
-	FilterEndpointSpec(MessageFilter messageFilter) {
+	protected FilterEndpointSpec(MessageFilter messageFilter) {
 		super(messageFilter);
 	}
 
diff --git a/spring-integration-core/src/main/java/org/springframework/integration/dsl/FluxMessageChannelSpec.java b/spring-integration-core/src/main/java/org/springframework/integration/dsl/FluxMessageChannelSpec.java
index 9860b251d7..6d0eb4f728 100644
--- a/spring-integration-core/src/main/java/org/springframework/integration/dsl/FluxMessageChannelSpec.java
+++ b/spring-integration-core/src/main/java/org/springframework/integration/dsl/FluxMessageChannelSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2017-2019 the original author or authors.
+ * Copyright 2017-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -26,7 +26,7 @@ import org.springframework.integration.channel.FluxMessageChannel;
  */
 public class FluxMessageChannelSpec extends MessageChannelSpec<FluxMessageChannelSpec, FluxMessageChannel> {
 
-	FluxMessageChannelSpec() {
+	protected FluxMessageChannelSpec() {
 		this.channel = new FluxMessageChannel();
 	}
 
diff --git a/spring-integration-core/src/main/java/org/springframework/integration/dsl/GatewayEndpointSpec.java b/spring-integration-core/src/main/java/org/springframework/integration/dsl/GatewayEndpointSpec.java
index 01452d64b0..64fa3d005e 100644
--- a/spring-integration-core/src/main/java/org/springframework/integration/dsl/GatewayEndpointSpec.java
+++ b/spring-integration-core/src/main/java/org/springframework/integration/dsl/GatewayEndpointSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -26,43 +26,73 @@ import org.springframework.messaging.MessageChannel;
  *
  * @since 5.0
  */
-public final class GatewayEndpointSpec extends ConsumerEndpointSpec<GatewayEndpointSpec, GatewayMessageHandler> {
+public class GatewayEndpointSpec extends ConsumerEndpointSpec<GatewayEndpointSpec, GatewayMessageHandler> {
 
-	GatewayEndpointSpec(MessageChannel requestChannel) {
+	protected GatewayEndpointSpec(MessageChannel requestChannel) {
 		super(new GatewayMessageHandler());
 		this.handler.setRequestChannel(requestChannel);
 	}
 
-	GatewayEndpointSpec(String requestChannel) {
+	protected GatewayEndpointSpec(String requestChannel) {
 		super(new GatewayMessageHandler());
 		this.handler.setRequestChannelName(requestChannel);
 	}
 
+	/**
+	 * Set a reply channel.
+	 * @param replyChannel the reply channel
+	 * @return the spec
+	 */
 	public GatewayEndpointSpec replyChannel(MessageChannel replyChannel) {
 		this.handler.setReplyChannel(replyChannel);
 		return this;
 	}
 
+	/**
+	 * Set a reply channel.
+	 * @param replyChannel the reply channel
+	 * @return the spec
+	 */
 	public GatewayEndpointSpec replyChannel(String replyChannel) {
 		this.handler.setReplyChannelName(replyChannel);
 		return this;
 	}
 
+	/**
+	 * Set an error channel.
+	 * @param errorChannel the error channel
+	 * @return the spec
+	 */
 	public GatewayEndpointSpec errorChannel(MessageChannel errorChannel) {
 		this.handler.setErrorChannel(errorChannel);
 		return this;
 	}
 
+	/**
+	 * Set an error channel.
+	 * @param errorChannel the error channel
+	 * @return the spec
+	 */
 	public GatewayEndpointSpec errorChannel(String errorChannel) {
 		this.handler.setErrorChannelName(errorChannel);
 		return this;
 	}
 
+	/**
+	 * Set a request timeout.
+	 * @param requestTimeout the request timeout
+	 * @return the spec
+	 */
 	public GatewayEndpointSpec requestTimeout(Long requestTimeout) {
 		this.handler.setRequestTimeout(requestTimeout);
 		return this;
 	}
 
+	/**
+	 * Set a reply timeout.
+	 * @param replyTimeout the reply timeout
+	 * @return the spec
+	 */
 	public GatewayEndpointSpec replyTimeout(Long replyTimeout) {
 		this.handler.setReplyTimeout(replyTimeout);
 		return this;
diff --git a/spring-integration-core/src/main/java/org/springframework/integration/dsl/GatewayProxySpec.java b/spring-integration-core/src/main/java/org/springframework/integration/dsl/GatewayProxySpec.java
index 2987b201e1..67b7d119e1 100644
--- a/spring-integration-core/src/main/java/org/springframework/integration/dsl/GatewayProxySpec.java
+++ b/spring-integration-core/src/main/java/org/springframework/integration/dsl/GatewayProxySpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2019 the original author or authors.
+ * Copyright 2019-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -45,19 +45,19 @@ import org.springframework.messaging.MessageChannel;
  */
 public class GatewayProxySpec {
 
-	private static final SpelExpressionParser PARSER = new SpelExpressionParser();
+	protected  static final SpelExpressionParser PARSER = new SpelExpressionParser(); // NOSONAR - final
 
-	private final MessageChannel gatewayRequestChannel = new DirectChannel();
+	protected final MessageChannel gatewayRequestChannel = new DirectChannel(); // NOSONAR - final
 
-	private final GatewayProxyFactoryBean gatewayProxyFactoryBean;
+	protected final GatewayProxyFactoryBean gatewayProxyFactoryBean; // NOSONAR - final
 
-	private final GatewayMethodMetadata gatewayMethodMetadata = new GatewayMethodMetadata();
+	protected final GatewayMethodMetadata gatewayMethodMetadata = new GatewayMethodMetadata(); // NOSONAR - final
 
-	private final Map<String, Expression> headerExpressions = new HashMap<>();
+	protected final Map<String, Expression> headerExpressions = new HashMap<>(); // NOSONAR - final
 
 	private boolean populateGatewayMethodMetadata;
 
-	GatewayProxySpec(Class<?> serviceInterface) {
+	protected GatewayProxySpec(Class<?> serviceInterface) {
 		this.gatewayProxyFactoryBean = new AnnotationGatewayProxyFactoryBean(serviceInterface);
 		this.gatewayProxyFactoryBean.setDefaultRequestChannel(this.gatewayRequestChannel);
 	}
diff --git a/spring-integration-core/src/main/java/org/springframework/integration/dsl/GenericEndpointSpec.java b/spring-integration-core/src/main/java/org/springframework/integration/dsl/GenericEndpointSpec.java
index eb6928f903..1a634733ca 100644
--- a/spring-integration-core/src/main/java/org/springframework/integration/dsl/GenericEndpointSpec.java
+++ b/spring-integration-core/src/main/java/org/springframework/integration/dsl/GenericEndpointSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -27,10 +27,10 @@ import org.springframework.messaging.MessageHandler;
  *
  * @since 5.0
  */
-public final class GenericEndpointSpec<H extends MessageHandler>
+public class GenericEndpointSpec<H extends MessageHandler>
 		extends ConsumerEndpointSpec<GenericEndpointSpec<H>, H> {
 
-	GenericEndpointSpec(H messageHandler) {
+	protected GenericEndpointSpec(H messageHandler) {
 		super(messageHandler);
 	}
 
diff --git a/spring-integration-core/src/main/java/org/springframework/integration/dsl/HeaderEnricherSpec.java b/spring-integration-core/src/main/java/org/springframework/integration/dsl/HeaderEnricherSpec.java
index e3f162c3fa..1b529c93fe 100644
--- a/spring-integration-core/src/main/java/org/springframework/integration/dsl/HeaderEnricherSpec.java
+++ b/spring-integration-core/src/main/java/org/springframework/integration/dsl/HeaderEnricherSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -58,11 +58,11 @@ public class HeaderEnricherSpec extends ConsumerEndpointSpec<HeaderEnricherSpec,
 
 	private static final String HEADERS_MUST_NOT_BE_NULL = "'headers' must not be null";
 
-	private final Map<String, HeaderValueMessageProcessor<?>> headerToAdd = new HashMap<>();
+	protected final Map<String, HeaderValueMessageProcessor<?>> headerToAdd = new HashMap<>(); // NOSONAR - final
 
-	private final HeaderEnricher headerEnricher = new HeaderEnricher(this.headerToAdd);
+	protected final HeaderEnricher headerEnricher = new HeaderEnricher(this.headerToAdd); // NOSONAR - final
 
-	HeaderEnricherSpec() {
+	protected HeaderEnricherSpec() {
 		super(null);
 		this.handler = new MessageTransformingHandler(this.headerEnricher);
 	}
diff --git a/spring-integration-core/src/main/java/org/springframework/integration/dsl/IntegrationFlowExtension.java b/spring-integration-core/src/main/java/org/springframework/integration/dsl/IntegrationFlowExtension.java
new file mode 100644
index 0000000000..3bbcf34e2b
--- /dev/null
+++ b/spring-integration-core/src/main/java/org/springframework/integration/dsl/IntegrationFlowExtension.java
@@ -0,0 +1,98 @@
+/*
+ * Copyright 2020 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.integration.dsl;
+
+import java.util.Map;
+
+import org.springframework.beans.factory.BeanNameAware;
+import org.springframework.integration.channel.DirectChannel;
+
+/**
+ * An {@link IntegrationFlowDefinition} extension for custom Java DSL operators
+ * and reusable solutions.
+ * For supporting method flow chain an implementation of this class has to return
+ * an extension class from new methods, e.g.:
+ * <pre class="code">
+ * {@code
+ * 	public class MyIntegrationFlowDefinition
+ * 			extends IntegrationFlowExtension<MyIntegrationFlowDefinition> {
+ *
+ * 		public MyIntegrationFlowDefinition upperCaseAfterSplit() {
+ * 			return split()
+ * 					.transform("payload.toUpperCase()");
+ *      }
+ * }
+ * }
+ * </pre>
+ * This way it will be used in the target configuration as natural DSL definition:
+ * <pre class="code">
+ * {@code
+ *  &#064;Bean
+ *  public IntegrationFlow myFlowDefinition() {
+ * 		return
+ * 				new MyIntegrationFlowDefinition()
+ * 			            .log()
+ * 						.upperCaseAfterSplit()
+ * 						.aggregate()
+ * 						.get();
+ *  }
+ * }
+ * </pre>
+ * This {@link IntegrationFlowExtension} can also be used for overriding
+ * existing operators with extensions to any {@link IntegrationComponentSpec} extensions,
+ * e.g. adding new options for target component configuration.
+ *
+ * @param <B> the {@link IntegrationFlowDefinition} implementation type.
+ *
+ * @author Artem Bilan
+ *
+ * @since 5.3
+ */
+public abstract class IntegrationFlowExtension<B extends IntegrationFlowExtension<B>>
+		extends IntegrationFlowDefinition<B> {
+
+	private final DirectChannel inputChannel = new DirectChannel();
+
+	protected IntegrationFlowExtension() {
+		channel(this.inputChannel);
+	}
+
+	@Override
+	public StandardIntegrationFlow get() {
+		StandardIntegrationFlow targetIntegrationFlow = super.get();
+		return new StandardIntegrationFlowExtension(targetIntegrationFlow.getIntegrationComponents(),
+				this.inputChannel);
+	}
+
+	private static class StandardIntegrationFlowExtension extends StandardIntegrationFlow
+			implements BeanNameAware {
+
+		private final DirectChannel inputChannel;
+
+		StandardIntegrationFlowExtension(Map<Object, String> integrationComponents, DirectChannel inputChannel) {
+			super(integrationComponents);
+			this.inputChannel = inputChannel;
+		}
+
+		@Override
+		public void setBeanName(String name) {
+			this.inputChannel.setBeanName(name + ".input");
+		}
+
+	}
+
+}
diff --git a/spring-integration-core/src/main/java/org/springframework/integration/dsl/PriorityChannelSpec.java b/spring-integration-core/src/main/java/org/springframework/integration/dsl/PriorityChannelSpec.java
index 84aad87957..ae41ed2b82 100644
--- a/spring-integration-core/src/main/java/org/springframework/integration/dsl/PriorityChannelSpec.java
+++ b/spring-integration-core/src/main/java/org/springframework/integration/dsl/PriorityChannelSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -37,7 +37,7 @@ public class PriorityChannelSpec extends MessageChannelSpec<PriorityChannelSpec,
 
 	private MessageGroupQueue messageGroupQueue;
 
-	PriorityChannelSpec() {
+	protected PriorityChannelSpec() {
 	}
 
 	public PriorityChannelSpec capacity(int capacity) {
diff --git a/spring-integration-core/src/main/java/org/springframework/integration/dsl/PublishSubscribeSpec.java b/spring-integration-core/src/main/java/org/springframework/integration/dsl/PublishSubscribeSpec.java
index e9108290a5..21df90a866 100644
--- a/spring-integration-core/src/main/java/org/springframework/integration/dsl/PublishSubscribeSpec.java
+++ b/spring-integration-core/src/main/java/org/springframework/integration/dsl/PublishSubscribeSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -36,10 +36,10 @@ public class PublishSubscribeSpec extends PublishSubscribeChannelSpec<PublishSub
 
 	private int order;
 
-	PublishSubscribeSpec() {
+	protected PublishSubscribeSpec() {
 	}
 
-	PublishSubscribeSpec(@Nullable Executor executor) {
+	protected PublishSubscribeSpec(@Nullable Executor executor) {
 		super(executor);
 	}
 
diff --git a/spring-integration-core/src/main/java/org/springframework/integration/dsl/QueueChannelSpec.java b/spring-integration-core/src/main/java/org/springframework/integration/dsl/QueueChannelSpec.java
index 07a4cc1604..675d4bfcd3 100644
--- a/spring-integration-core/src/main/java/org/springframework/integration/dsl/QueueChannelSpec.java
+++ b/spring-integration-core/src/main/java/org/springframework/integration/dsl/QueueChannelSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -35,14 +35,14 @@ public class QueueChannelSpec extends MessageChannelSpec<QueueChannelSpec, Queue
 
 	protected Integer capacity; // NOSONAR
 
-	QueueChannelSpec() {
+	protected QueueChannelSpec() {
 	}
 
-	QueueChannelSpec(Queue<Message<?>> queue) {
+	protected QueueChannelSpec(Queue<Message<?>> queue) {
 		this.queue = queue;
 	}
 
-	QueueChannelSpec(Integer capacity) {
+	protected QueueChannelSpec(Integer capacity) {
 		this.capacity = capacity;
 	}
 
@@ -71,7 +71,7 @@ public class QueueChannelSpec extends MessageChannelSpec<QueueChannelSpec, Queue
 
 		private Lock storeLock;
 
-		MessageStoreSpec(ChannelMessageStore messageGroupStore, Object groupId) {
+		protected MessageStoreSpec(ChannelMessageStore messageGroupStore, Object groupId) {
 			this.messageGroupStore = messageGroupStore;
 			this.groupId = groupId;
 		}
diff --git a/spring-integration-core/src/main/java/org/springframework/integration/dsl/RecipientListRouterSpec.java b/spring-integration-core/src/main/java/org/springframework/integration/dsl/RecipientListRouterSpec.java
index 1c2a15300c..4c298d9cd7 100644
--- a/spring-integration-core/src/main/java/org/springframework/integration/dsl/RecipientListRouterSpec.java
+++ b/spring-integration-core/src/main/java/org/springframework/integration/dsl/RecipientListRouterSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -36,7 +36,7 @@ import org.springframework.util.StringUtils;
  */
 public class RecipientListRouterSpec extends AbstractRouterSpec<RecipientListRouterSpec, RecipientListRouter> {
 
-	RecipientListRouterSpec() {
+	protected RecipientListRouterSpec() {
 		super(new RecipientListRouter());
 	}
 
diff --git a/spring-integration-core/src/main/java/org/springframework/integration/dsl/RendezvousChannelSpec.java b/spring-integration-core/src/main/java/org/springframework/integration/dsl/RendezvousChannelSpec.java
index 9ea1a763d9..498b4ede6c 100644
--- a/spring-integration-core/src/main/java/org/springframework/integration/dsl/RendezvousChannelSpec.java
+++ b/spring-integration-core/src/main/java/org/springframework/integration/dsl/RendezvousChannelSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -25,7 +25,7 @@ import org.springframework.integration.channel.RendezvousChannel;
  */
 public class RendezvousChannelSpec extends MessageChannelSpec<RendezvousChannelSpec, RendezvousChannel> {
 
-	RendezvousChannelSpec() {
+	protected RendezvousChannelSpec() {
 		this.channel = new RendezvousChannel();
 	}
 
diff --git a/spring-integration-core/src/main/java/org/springframework/integration/dsl/ResequencerSpec.java b/spring-integration-core/src/main/java/org/springframework/integration/dsl/ResequencerSpec.java
index 3f0bcb00ed..3a991b3d5b 100644
--- a/spring-integration-core/src/main/java/org/springframework/integration/dsl/ResequencerSpec.java
+++ b/spring-integration-core/src/main/java/org/springframework/integration/dsl/ResequencerSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -26,7 +26,7 @@ import org.springframework.integration.aggregator.ResequencingMessageHandler;
  */
 public class ResequencerSpec extends CorrelationHandlerSpec<ResequencerSpec, ResequencingMessageHandler> {
 
-	ResequencerSpec() {
+	protected ResequencerSpec() {
 		super(new ResequencingMessageHandler(new ResequencingMessageGroupProcessor()));
 	}
 
diff --git a/spring-integration-core/src/main/java/org/springframework/integration/dsl/RouterSpec.java b/spring-integration-core/src/main/java/org/springframework/integration/dsl/RouterSpec.java
index 14f19a532f..f512aa8ed2 100644
--- a/spring-integration-core/src/main/java/org/springframework/integration/dsl/RouterSpec.java
+++ b/spring-integration-core/src/main/java/org/springframework/integration/dsl/RouterSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -52,7 +52,7 @@ public final class RouterSpec<K, R extends AbstractMappingMessageRouter>
 
 	private boolean mappingProviderRegistered;
 
-	RouterSpec(R router) {
+	protected RouterSpec(R router) {
 		super(router);
 		this.mappingProvider = new RouterMappingProvider(this.handler);
 	}
diff --git a/spring-integration-core/src/main/java/org/springframework/integration/dsl/ScatterGatherSpec.java b/spring-integration-core/src/main/java/org/springframework/integration/dsl/ScatterGatherSpec.java
index f84122d0ef..96e58504cb 100644
--- a/spring-integration-core/src/main/java/org/springframework/integration/dsl/ScatterGatherSpec.java
+++ b/spring-integration-core/src/main/java/org/springframework/integration/dsl/ScatterGatherSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -31,7 +31,7 @@ import org.springframework.messaging.MessageChannel;
  */
 public class ScatterGatherSpec extends ConsumerEndpointSpec<ScatterGatherSpec, ScatterGatherHandler> {
 
-	ScatterGatherSpec(ScatterGatherHandler messageHandler) {
+	protected ScatterGatherSpec(ScatterGatherHandler messageHandler) {
 		super(messageHandler);
 	}
 
diff --git a/spring-integration-core/src/main/java/org/springframework/integration/dsl/SourcePollingChannelAdapterSpec.java b/spring-integration-core/src/main/java/org/springframework/integration/dsl/SourcePollingChannelAdapterSpec.java
index ab30ea3352..4cee04531f 100644
--- a/spring-integration-core/src/main/java/org/springframework/integration/dsl/SourcePollingChannelAdapterSpec.java
+++ b/spring-integration-core/src/main/java/org/springframework/integration/dsl/SourcePollingChannelAdapterSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -25,10 +25,10 @@ import org.springframework.integration.scheduling.PollerMetadata;
  *
  * @since 5.0
  */
-public final class SourcePollingChannelAdapterSpec extends
+public class SourcePollingChannelAdapterSpec extends
 		EndpointSpec<SourcePollingChannelAdapterSpec, SourcePollingChannelAdapterFactoryBean, MessageSource<?>> {
 
-	SourcePollingChannelAdapterSpec(MessageSource<?> messageSource) {
+	protected SourcePollingChannelAdapterSpec(MessageSource<?> messageSource) {
 		super(messageSource);
 		this.endpointFactoryBean.setSource(messageSource);
 	}
diff --git a/spring-integration-core/src/main/java/org/springframework/integration/dsl/SplitterEndpointSpec.java b/spring-integration-core/src/main/java/org/springframework/integration/dsl/SplitterEndpointSpec.java
index 6191bcb6ba..d26695e7b7 100644
--- a/spring-integration-core/src/main/java/org/springframework/integration/dsl/SplitterEndpointSpec.java
+++ b/spring-integration-core/src/main/java/org/springframework/integration/dsl/SplitterEndpointSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -29,10 +29,10 @@ import org.springframework.messaging.MessageChannel;
  *
  * @since 5.0
  */
-public final class SplitterEndpointSpec<S extends AbstractMessageSplitter>
+public class SplitterEndpointSpec<S extends AbstractMessageSplitter>
 		extends ConsumerEndpointSpec<SplitterEndpointSpec<S>, S> {
 
-	SplitterEndpointSpec(S splitter) {
+	protected SplitterEndpointSpec(S splitter) {
 		super(splitter);
 	}
 
diff --git a/spring-integration-core/src/test/java/org/springframework/integration/dsl/extensions/IntegrationFlowExtensionTests.java b/spring-integration-core/src/test/java/org/springframework/integration/dsl/extensions/IntegrationFlowExtensionTests.java
new file mode 100644
index 0000000000..fb136540fa
--- /dev/null
+++ b/spring-integration-core/src/test/java/org/springframework/integration/dsl/extensions/IntegrationFlowExtensionTests.java
@@ -0,0 +1,117 @@
+/*
+ * Copyright 2020 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.integration.dsl.extensions;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.util.Arrays;
+import java.util.function.Consumer;
+import java.util.stream.Collectors;
+
+import org.junit.jupiter.api.Test;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.beans.factory.annotation.Qualifier;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.integration.channel.QueueChannel;
+import org.springframework.integration.config.EnableIntegration;
+import org.springframework.integration.dsl.AggregatorSpec;
+import org.springframework.integration.dsl.IntegrationFlow;
+import org.springframework.integration.dsl.IntegrationFlowExtension;
+import org.springframework.integration.support.MessageBuilder;
+import org.springframework.messaging.Message;
+import org.springframework.messaging.SubscribableChannel;
+import org.springframework.test.annotation.DirtiesContext;
+import org.springframework.test.context.junit.jupiter.SpringJUnitConfig;
+
+/**
+ * @author Artem Bilan
+ *
+ * @since 5.3
+ */
+@SpringJUnitConfig
+@DirtiesContext
+public class IntegrationFlowExtensionTests {
+
+	@Autowired
+	@Qualifier("customFlowDefinition.input")
+	SubscribableChannel customFlowDefinitionInput;
+
+	@Test
+	public void testCustomFlowDefinition() {
+		QueueChannel replyChannel = new QueueChannel();
+		Message<?> testMessage =
+				MessageBuilder.withPayload(Arrays.asList("one", "two", "three"))
+						.setReplyChannel(replyChannel)
+						.build();
+		this.customFlowDefinitionInput.send(testMessage);
+
+		Message<?> replyMessage = replyChannel.receive(10_000);
+
+		assertThat(replyMessage)
+				.isNotNull()
+				.extracting(Message::getPayload)
+				.isEqualTo("ONE, TWO, THREE");
+	}
+
+	@Configuration
+	@EnableIntegration
+	public static class ContextConfiguration {
+
+		@Bean
+		public IntegrationFlow customFlowDefinition() {
+			return
+					new CustomIntegrationFlowDefinition()
+							.log()
+							.upperCaseAfterSplit()
+							.channel("innerChannel")
+							.customAggregate(customAggregatorSpec ->
+									customAggregatorSpec.expireGroupsUponCompletion(true))
+							.logAndReply();
+		}
+
+	}
+
+	public static class CustomIntegrationFlowDefinition
+			extends IntegrationFlowExtension<CustomIntegrationFlowDefinition> {
+
+		public CustomIntegrationFlowDefinition upperCaseAfterSplit() {
+			return split()
+					.transform("payload.toUpperCase()");
+		}
+
+		public CustomIntegrationFlowDefinition customAggregate(Consumer<CustomAggregatorSpec> aggregator) {
+			return register(new CustomAggregatorSpec(), aggregator);
+		}
+
+	}
+
+	public static class CustomAggregatorSpec extends AggregatorSpec {
+
+		CustomAggregatorSpec() {
+			outputProcessor((group) ->
+					group.getMessages()
+							.stream()
+							.map(Message::getPayload)
+							.map(String.class::cast)
+							.collect(Collectors.joining(", ")));
+		}
+
+	}
+
+}
diff --git a/spring-integration-feed/src/main/java/org/springframework/integration/feed/dsl/FeedEntryMessageSourceSpec.java b/spring-integration-feed/src/main/java/org/springframework/integration/feed/dsl/FeedEntryMessageSourceSpec.java
index eba474ca7f..6fd6a5df65 100644
--- a/spring-integration-feed/src/main/java/org/springframework/integration/feed/dsl/FeedEntryMessageSourceSpec.java
+++ b/spring-integration-feed/src/main/java/org/springframework/integration/feed/dsl/FeedEntryMessageSourceSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -34,11 +34,11 @@ import com.rometools.rome.io.SyndFeedInput;
  */
 public class FeedEntryMessageSourceSpec extends MessageSourceSpec<FeedEntryMessageSourceSpec, FeedEntryMessageSource> {
 
-	FeedEntryMessageSourceSpec(URL feedUrl, String metadataKey) {
+	protected FeedEntryMessageSourceSpec(URL feedUrl, String metadataKey) {
 		this.target = new FeedEntryMessageSource(feedUrl, metadataKey);
 	}
 
-	FeedEntryMessageSourceSpec(Resource feedResource, String metadataKey) {
+	protected FeedEntryMessageSourceSpec(Resource feedResource, String metadataKey) {
 		this.target = new FeedEntryMessageSource(feedResource, metadataKey);
 	}
 
diff --git a/spring-integration-file/src/main/java/org/springframework/integration/file/dsl/FileInboundChannelAdapterSpec.java b/spring-integration-file/src/main/java/org/springframework/integration/file/dsl/FileInboundChannelAdapterSpec.java
index 0179e59c1e..fceed01f20 100644
--- a/spring-integration-file/src/main/java/org/springframework/integration/file/dsl/FileInboundChannelAdapterSpec.java
+++ b/spring-integration-file/src/main/java/org/springframework/integration/file/dsl/FileInboundChannelAdapterSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -46,7 +46,7 @@ public class FileInboundChannelAdapterSpec
 		extends MessageSourceSpec<FileInboundChannelAdapterSpec, FileReadingMessageSource>
 		implements ComponentsRegistration {
 
-	private final FileListFilterFactoryBean fileListFilterFactoryBean = new FileListFilterFactoryBean();
+	protected final FileListFilterFactoryBean fileListFilterFactoryBean = new FileListFilterFactoryBean(); // NOSONAR
 
 	private FileLocker locker;
 
@@ -56,11 +56,11 @@ public class FileInboundChannelAdapterSpec
 
 	private boolean filtersSet;
 
-	FileInboundChannelAdapterSpec() {
+	protected FileInboundChannelAdapterSpec() {
 		this.target = new FileReadingMessageSource();
 	}
 
-	FileInboundChannelAdapterSpec(Comparator<File> receptionOrderComparator) {
+	protected FileInboundChannelAdapterSpec(Comparator<File> receptionOrderComparator) {
 		this.target = new FileReadingMessageSource(receptionOrderComparator);
 	}
 
diff --git a/spring-integration-file/src/main/java/org/springframework/integration/file/dsl/FileSplitterSpec.java b/spring-integration-file/src/main/java/org/springframework/integration/file/dsl/FileSplitterSpec.java
index 617d50b2b1..a7435772c2 100644
--- a/spring-integration-file/src/main/java/org/springframework/integration/file/dsl/FileSplitterSpec.java
+++ b/spring-integration-file/src/main/java/org/springframework/integration/file/dsl/FileSplitterSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -45,15 +45,15 @@ public class FileSplitterSpec extends MessageHandlerSpec<FileSplitterSpec, FileS
 
 	private String firstLineHeaderName;
 
-	FileSplitterSpec() {
+	protected FileSplitterSpec() {
 		this(true);
 	}
 
-	FileSplitterSpec(boolean iterator) {
+	protected FileSplitterSpec(boolean iterator) {
 		this(iterator, false);
 	}
 
-	FileSplitterSpec(boolean iterator, boolean markers) {
+	protected FileSplitterSpec(boolean iterator, boolean markers) {
 		this.iterator = iterator;
 		this.markers = markers;
 	}
diff --git a/spring-integration-file/src/main/java/org/springframework/integration/file/dsl/FileWritingMessageHandlerSpec.java b/spring-integration-file/src/main/java/org/springframework/integration/file/dsl/FileWritingMessageHandlerSpec.java
index bab4107ef7..fced6476b6 100644
--- a/spring-integration-file/src/main/java/org/springframework/integration/file/dsl/FileWritingMessageHandlerSpec.java
+++ b/spring-integration-file/src/main/java/org/springframework/integration/file/dsl/FileWritingMessageHandlerSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -49,19 +49,19 @@ public class FileWritingMessageHandlerSpec
 
 	private DefaultFileNameGenerator defaultFileNameGenerator;
 
-	FileWritingMessageHandlerSpec(File destinationDirectory) {
+	protected FileWritingMessageHandlerSpec(File destinationDirectory) {
 		this.target = new FileWritingMessageHandler(destinationDirectory);
 	}
 
-	FileWritingMessageHandlerSpec(String directoryExpression) {
+	protected FileWritingMessageHandlerSpec(String directoryExpression) {
 		this(PARSER.parseExpression(directoryExpression));
 	}
 
-	<P> FileWritingMessageHandlerSpec(Function<Message<P>, ?> directoryFunction) {
+	protected <P> FileWritingMessageHandlerSpec(Function<Message<P>, ?> directoryFunction) {
 		this(new FunctionExpression<>(directoryFunction));
 	}
 
-	FileWritingMessageHandlerSpec(Expression directoryExpression) {
+	protected FileWritingMessageHandlerSpec(Expression directoryExpression) {
 		this.target = new FileWritingMessageHandler(directoryExpression);
 	}
 
diff --git a/spring-integration-file/src/main/java/org/springframework/integration/file/dsl/TailAdapterSpec.java b/spring-integration-file/src/main/java/org/springframework/integration/file/dsl/TailAdapterSpec.java
index cd2edb739a..12f8d5a036 100644
--- a/spring-integration-file/src/main/java/org/springframework/integration/file/dsl/TailAdapterSpec.java
+++ b/spring-integration-file/src/main/java/org/springframework/integration/file/dsl/TailAdapterSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -43,12 +43,12 @@ public class TailAdapterSpec extends MessageProducerSpec<TailAdapterSpec, FileTa
 
 	private MessageChannel errorChannel;
 
-	TailAdapterSpec() {
+	protected TailAdapterSpec() {
 		super(null);
 		this.factoryBean.setBeanFactory(new DefaultListableBeanFactory());
 	}
 
-	TailAdapterSpec file(File file) {
+	protected TailAdapterSpec file(File file) {
 		Assert.notNull(file, "'file' cannot be null");
 		this.factoryBean.setFile(file);
 		return _this();
diff --git a/spring-integration-ftp/src/main/java/org/springframework/integration/ftp/dsl/FtpInboundChannelAdapterSpec.java b/spring-integration-ftp/src/main/java/org/springframework/integration/ftp/dsl/FtpInboundChannelAdapterSpec.java
index f9a3f9a36d..3d4f520f8c 100644
--- a/spring-integration-ftp/src/main/java/org/springframework/integration/ftp/dsl/FtpInboundChannelAdapterSpec.java
+++ b/spring-integration-ftp/src/main/java/org/springframework/integration/ftp/dsl/FtpInboundChannelAdapterSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2014-2019 the original author or authors.
+ * Copyright 2014-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -44,7 +44,7 @@ public class FtpInboundChannelAdapterSpec
 		extends RemoteFileInboundChannelAdapterSpec<FTPFile, FtpInboundChannelAdapterSpec,
 				FtpInboundFileSynchronizingMessageSource> {
 
-	FtpInboundChannelAdapterSpec(SessionFactory<FTPFile> sessionFactory, Comparator<File> comparator) {
+	protected FtpInboundChannelAdapterSpec(SessionFactory<FTPFile> sessionFactory, Comparator<File> comparator) {
 		super(new FtpInboundFileSynchronizer(sessionFactory));
 		this.target = new FtpInboundFileSynchronizingMessageSource(this.synchronizer, comparator);
 	}
diff --git a/spring-integration-ftp/src/main/java/org/springframework/integration/ftp/dsl/FtpMessageHandlerSpec.java b/spring-integration-ftp/src/main/java/org/springframework/integration/ftp/dsl/FtpMessageHandlerSpec.java
index 260ae0d8cb..cc2d953b1b 100644
--- a/spring-integration-ftp/src/main/java/org/springframework/integration/ftp/dsl/FtpMessageHandlerSpec.java
+++ b/spring-integration-ftp/src/main/java/org/springframework/integration/ftp/dsl/FtpMessageHandlerSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2014-2019 the original author or authors.
+ * Copyright 2014-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -34,15 +34,15 @@ import org.springframework.integration.ftp.outbound.FtpMessageHandler;
  */
 public class FtpMessageHandlerSpec extends FileTransferringMessageHandlerSpec<FTPFile, FtpMessageHandlerSpec> {
 
-	FtpMessageHandlerSpec(SessionFactory<FTPFile> sessionFactory) {
+	protected FtpMessageHandlerSpec(SessionFactory<FTPFile> sessionFactory) {
 		this.target = new FtpMessageHandler(sessionFactory);
 	}
 
-	FtpMessageHandlerSpec(RemoteFileTemplate<FTPFile> remoteFileTemplate) {
+	protected FtpMessageHandlerSpec(RemoteFileTemplate<FTPFile> remoteFileTemplate) {
 		this.target = new FtpMessageHandler(remoteFileTemplate.getSessionFactory());
 	}
 
-	FtpMessageHandlerSpec(RemoteFileTemplate<FTPFile> remoteFileTemplate, FileExistsMode fileExistsMode) {
+	protected FtpMessageHandlerSpec(RemoteFileTemplate<FTPFile> remoteFileTemplate, FileExistsMode fileExistsMode) {
 		this.target = new FtpMessageHandler(remoteFileTemplate, fileExistsMode);
 	}
 
diff --git a/spring-integration-ftp/src/main/java/org/springframework/integration/ftp/dsl/FtpOutboundGatewaySpec.java b/spring-integration-ftp/src/main/java/org/springframework/integration/ftp/dsl/FtpOutboundGatewaySpec.java
index 747ae459d0..c15fdce7b3 100644
--- a/spring-integration-ftp/src/main/java/org/springframework/integration/ftp/dsl/FtpOutboundGatewaySpec.java
+++ b/spring-integration-ftp/src/main/java/org/springframework/integration/ftp/dsl/FtpOutboundGatewaySpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2014-2019 the original author or authors.
+ * Copyright 2014-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -37,7 +37,7 @@ import org.springframework.messaging.Message;
  */
 public class FtpOutboundGatewaySpec extends RemoteFileOutboundGatewaySpec<FTPFile, FtpOutboundGatewaySpec> {
 
-	FtpOutboundGatewaySpec(FtpOutboundGateway outboundGateway) {
+	protected FtpOutboundGatewaySpec(FtpOutboundGateway outboundGateway) {
 		super(outboundGateway);
 	}
 
diff --git a/spring-integration-ftp/src/main/java/org/springframework/integration/ftp/dsl/FtpStreamingInboundChannelAdapterSpec.java b/spring-integration-ftp/src/main/java/org/springframework/integration/ftp/dsl/FtpStreamingInboundChannelAdapterSpec.java
index 355e251941..2309c4a2b9 100644
--- a/spring-integration-ftp/src/main/java/org/springframework/integration/ftp/dsl/FtpStreamingInboundChannelAdapterSpec.java
+++ b/spring-integration-ftp/src/main/java/org/springframework/integration/ftp/dsl/FtpStreamingInboundChannelAdapterSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2014-2019 the original author or authors.
+ * Copyright 2014-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -31,18 +31,20 @@ import org.springframework.integration.ftp.inbound.FtpStreamingMessageSource;
 import org.springframework.integration.metadata.SimpleMetadataStore;
 
 /**
- * A {@link RemoteFileStreamingInboundChannelAdapterSpec} for a
- * {@link FtpStreamingMessageSource}.
+ * A {@link RemoteFileStreamingInboundChannelAdapterSpec} for a {@link FtpStreamingMessageSource}.
  *
  * @author Gary Russell
+ * @author Artem Bilan
+ *
  * @since 5.0
  */
 public class FtpStreamingInboundChannelAdapterSpec
 		extends RemoteFileStreamingInboundChannelAdapterSpec<FTPFile, FtpStreamingInboundChannelAdapterSpec,
 				FtpStreamingMessageSource> {
 
-	FtpStreamingInboundChannelAdapterSpec(RemoteFileTemplate<FTPFile> remoteFileTemplate,
+	protected FtpStreamingInboundChannelAdapterSpec(RemoteFileTemplate<FTPFile> remoteFileTemplate,
 			Comparator<FTPFile> comparator) {
+
 		this.target = new FtpStreamingMessageSource(remoteFileTemplate, comparator);
 	}
 
@@ -68,7 +70,6 @@ public class FtpStreamingInboundChannelAdapterSpec
 		return filter(composeFilters(new FtpRegexPatternFileListFilter(regex)));
 	}
 
-	@SuppressWarnings("unchecked")
 	private CompositeFileListFilter<FTPFile> composeFilters(FileListFilter<FTPFile> fileListFilter) {
 		CompositeFileListFilter<FTPFile> compositeFileListFilter = new CompositeFileListFilter<>();
 		compositeFileListFilter.addFilters(fileListFilter,
diff --git a/spring-integration-http/src/main/java/org/springframework/integration/http/dsl/BaseHttpInboundEndpointSpec.java b/spring-integration-http/src/main/java/org/springframework/integration/http/dsl/BaseHttpInboundEndpointSpec.java
index d58a648398..451ba31d1b 100644
--- a/spring-integration-http/src/main/java/org/springframework/integration/http/dsl/BaseHttpInboundEndpointSpec.java
+++ b/spring-integration-http/src/main/java/org/springframework/integration/http/dsl/BaseHttpInboundEndpointSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -38,7 +38,7 @@ public abstract class BaseHttpInboundEndpointSpec<S extends BaseHttpInboundEndpo
 		E extends HttpRequestHandlingEndpointSupport>
 		extends HttpInboundEndpointSupportSpec<S, E> {
 
-	BaseHttpInboundEndpointSpec(E endpoint, String... path) {
+	protected BaseHttpInboundEndpointSpec(E endpoint, String... path) {
 		super(endpoint, path);
 	}
 
diff --git a/spring-integration-http/src/main/java/org/springframework/integration/http/dsl/HttpControllerEndpointSpec.java b/spring-integration-http/src/main/java/org/springframework/integration/http/dsl/HttpControllerEndpointSpec.java
index b23cf92a19..6266682a39 100644
--- a/spring-integration-http/src/main/java/org/springframework/integration/http/dsl/HttpControllerEndpointSpec.java
+++ b/spring-integration-http/src/main/java/org/springframework/integration/http/dsl/HttpControllerEndpointSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -30,7 +30,7 @@ import org.springframework.integration.http.inbound.HttpRequestHandlingControlle
 public class HttpControllerEndpointSpec
 		extends BaseHttpInboundEndpointSpec<HttpControllerEndpointSpec, HttpRequestHandlingController> {
 
-	HttpControllerEndpointSpec(HttpRequestHandlingController controller, String... path) {
+	protected HttpControllerEndpointSpec(HttpRequestHandlingController controller, String... path) {
 		super(controller, path);
 	}
 
diff --git a/spring-integration-http/src/main/java/org/springframework/integration/http/dsl/HttpMessageHandlerSpec.java b/spring-integration-http/src/main/java/org/springframework/integration/http/dsl/HttpMessageHandlerSpec.java
index bc1861e8e7..e0951deeba 100644
--- a/spring-integration-http/src/main/java/org/springframework/integration/http/dsl/HttpMessageHandlerSpec.java
+++ b/spring-integration-http/src/main/java/org/springframework/integration/http/dsl/HttpMessageHandlerSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -45,15 +45,15 @@ public class HttpMessageHandlerSpec
 
 	private final RestTemplate restTemplate;
 
-	HttpMessageHandlerSpec(URI uri, RestTemplate restTemplate) {
+	protected HttpMessageHandlerSpec(URI uri, RestTemplate restTemplate) {
 		this(new ValueExpression<>(uri), restTemplate);
 	}
 
-	HttpMessageHandlerSpec(String uri, RestTemplate restTemplate) {
+	protected HttpMessageHandlerSpec(String uri, RestTemplate restTemplate) {
 		this(new LiteralExpression(uri), restTemplate);
 	}
 
-	HttpMessageHandlerSpec(Expression uriExpression, RestTemplate restTemplate) {
+	protected HttpMessageHandlerSpec(Expression uriExpression, RestTemplate restTemplate) {
 		super(new HttpRequestExecutingMessageHandler(uriExpression, restTemplate));
 		this.restTemplate = restTemplate;
 	}
diff --git a/spring-integration-http/src/main/java/org/springframework/integration/http/dsl/HttpRequestHandlerEndpointSpec.java b/spring-integration-http/src/main/java/org/springframework/integration/http/dsl/HttpRequestHandlerEndpointSpec.java
index e94feeb8e2..d038c802cc 100644
--- a/spring-integration-http/src/main/java/org/springframework/integration/http/dsl/HttpRequestHandlerEndpointSpec.java
+++ b/spring-integration-http/src/main/java/org/springframework/integration/http/dsl/HttpRequestHandlerEndpointSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -30,7 +30,7 @@ import org.springframework.integration.http.inbound.HttpRequestHandlingMessaging
 public class HttpRequestHandlerEndpointSpec
 		extends BaseHttpInboundEndpointSpec<HttpRequestHandlerEndpointSpec, HttpRequestHandlingMessagingGateway> {
 
-	HttpRequestHandlerEndpointSpec(HttpRequestHandlingMessagingGateway endpoint, String... path) {
+	protected HttpRequestHandlerEndpointSpec(HttpRequestHandlingMessagingGateway endpoint, String... path) {
 		super(endpoint, path);
 	}
 
diff --git a/spring-integration-ip/src/main/java/org/springframework/integration/ip/dsl/AbstractConnectionFactorySpec.java b/spring-integration-ip/src/main/java/org/springframework/integration/ip/dsl/AbstractConnectionFactorySpec.java
index 65a91f828c..788adcf0bb 100644
--- a/spring-integration-ip/src/main/java/org/springframework/integration/ip/dsl/AbstractConnectionFactorySpec.java
+++ b/spring-integration-ip/src/main/java/org/springframework/integration/ip/dsl/AbstractConnectionFactorySpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -28,10 +28,13 @@ import org.springframework.integration.ip.tcp.connection.TcpSocketSupport;
 
 /**
  * An {@link IntegrationComponentSpec} for {@link AbstractConnectionFactory}s.
+ *
  * @param <S> the target {@link AbstractConnectionFactorySpec} implementation type.
  * @param <C> the target {@link AbstractConnectionFactory} implementation type.
  *
  * @author Gary Russell
+ * @author Artem Bilan
+ *
  * @since 5.0
  *
  */
@@ -39,7 +42,7 @@ public abstract class AbstractConnectionFactorySpec
 			<S extends AbstractConnectionFactorySpec<S, C>, C extends AbstractConnectionFactory>
 		extends IntegrationComponentSpec<S, C> {
 
-	AbstractConnectionFactorySpec(C connectionFactory) {
+	protected AbstractConnectionFactorySpec(C connectionFactory) {
 		this.target = connectionFactory;
 	}
 
diff --git a/spring-integration-ip/src/main/java/org/springframework/integration/ip/dsl/AbstractUdpOutboundChannelAdapterSpec.java b/spring-integration-ip/src/main/java/org/springframework/integration/ip/dsl/AbstractUdpOutboundChannelAdapterSpec.java
index e6afdd89c2..e3aa00c6e8 100644
--- a/spring-integration-ip/src/main/java/org/springframework/integration/ip/dsl/AbstractUdpOutboundChannelAdapterSpec.java
+++ b/spring-integration-ip/src/main/java/org/springframework/integration/ip/dsl/AbstractUdpOutboundChannelAdapterSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -30,6 +30,7 @@ import org.springframework.messaging.Message;
  * @param <S> the target {@link AbstractUdpOutboundChannelAdapterSpec} implementation type.
  *
  * @author Gary Russell
+ * @author Artem Bilan
  *
  * @since 5.0
  *
@@ -44,11 +45,11 @@ public abstract class AbstractUdpOutboundChannelAdapterSpec<S extends AbstractUd
 		this.target = new UnicastSendingMessageHandler(host, port);
 	}
 
-	AbstractUdpOutboundChannelAdapterSpec(String destinationExpression) {
+	protected AbstractUdpOutboundChannelAdapterSpec(String destinationExpression) {
 		this.target = new UnicastSendingMessageHandler(destinationExpression);
 	}
 
-	AbstractUdpOutboundChannelAdapterSpec(Function<Message<?>, ?> destinationFunction) {
+	protected AbstractUdpOutboundChannelAdapterSpec(Function<Message<?>, ?> destinationFunction) {
 		this.target = new UnicastSendingMessageHandler(new FunctionExpression<>(destinationFunction));
 	}
 
diff --git a/spring-integration-ip/src/main/java/org/springframework/integration/ip/dsl/TcpClientConnectionFactorySpec.java b/spring-integration-ip/src/main/java/org/springframework/integration/ip/dsl/TcpClientConnectionFactorySpec.java
index 7ac0738555..187190df78 100644
--- a/spring-integration-ip/src/main/java/org/springframework/integration/ip/dsl/TcpClientConnectionFactorySpec.java
+++ b/spring-integration-ip/src/main/java/org/springframework/integration/ip/dsl/TcpClientConnectionFactorySpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -22,7 +22,9 @@ import org.springframework.integration.ip.tcp.connection.TcpNioClientConnectionF
 
 /**
  * An {@link AbstractConnectionFactorySpec} for {@link AbstractClientConnectionFactory}s.
+ *
  * @author Gary Russell
+ * @author Artem Bilan
  *
  * @since 5.0
  *
@@ -30,11 +32,11 @@ import org.springframework.integration.ip.tcp.connection.TcpNioClientConnectionF
 public class TcpClientConnectionFactorySpec
 		extends AbstractConnectionFactorySpec<TcpClientConnectionFactorySpec, AbstractClientConnectionFactory> {
 
-	TcpClientConnectionFactorySpec(String host, int port) {
+	protected TcpClientConnectionFactorySpec(String host, int port) {
 		this(host, port, false);
 	}
 
-	TcpClientConnectionFactorySpec(String host, int port, boolean nio) {
+	protected TcpClientConnectionFactorySpec(String host, int port, boolean nio) {
 		super(nio ? new TcpNioClientConnectionFactory(host, port) : new TcpNetClientConnectionFactory(host, port));
 	}
 
diff --git a/spring-integration-ip/src/main/java/org/springframework/integration/ip/dsl/TcpInboundChannelAdapterSpec.java b/spring-integration-ip/src/main/java/org/springframework/integration/ip/dsl/TcpInboundChannelAdapterSpec.java
index 3d645d0e5b..4c3549a639 100644
--- a/spring-integration-ip/src/main/java/org/springframework/integration/ip/dsl/TcpInboundChannelAdapterSpec.java
+++ b/spring-integration-ip/src/main/java/org/springframework/integration/ip/dsl/TcpInboundChannelAdapterSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -38,13 +38,13 @@ public class TcpInboundChannelAdapterSpec
 		extends MessageProducerSpec<TcpInboundChannelAdapterSpec, TcpReceivingChannelAdapter>
 		implements ComponentsRegistration {
 
-	private final AbstractConnectionFactory connectionFactory;
+	protected final AbstractConnectionFactory connectionFactory; // NOSONAR - final
 
 	/**
 	 * Construct an instance using an existing spring-managed connection factory.
 	 * @param connectionFactoryBean the spring-managed bean.
 	 */
-	TcpInboundChannelAdapterSpec(AbstractConnectionFactory connectionFactoryBean) {
+	protected TcpInboundChannelAdapterSpec(AbstractConnectionFactory connectionFactoryBean) {
 		super(new TcpReceivingChannelAdapter());
 		this.connectionFactory = null;
 		this.target.setConnectionFactory(connectionFactoryBean);
@@ -54,7 +54,7 @@ public class TcpInboundChannelAdapterSpec
 	 * Construct an instance using the provided connection factory spec.
 	 * @param connectionFactorySpec the spec.
 	 */
-	TcpInboundChannelAdapterSpec(AbstractConnectionFactorySpec<?, ?> connectionFactorySpec) {
+	protected TcpInboundChannelAdapterSpec(AbstractConnectionFactorySpec<?, ?> connectionFactorySpec) {
 		super(new TcpReceivingChannelAdapter());
 		this.connectionFactory = connectionFactorySpec.get();
 		this.target.setConnectionFactory(this.connectionFactory);
diff --git a/spring-integration-ip/src/main/java/org/springframework/integration/ip/dsl/TcpInboundGatewaySpec.java b/spring-integration-ip/src/main/java/org/springframework/integration/ip/dsl/TcpInboundGatewaySpec.java
index 82af885f01..d24018b193 100644
--- a/spring-integration-ip/src/main/java/org/springframework/integration/ip/dsl/TcpInboundGatewaySpec.java
+++ b/spring-integration-ip/src/main/java/org/springframework/integration/ip/dsl/TcpInboundGatewaySpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -37,13 +37,13 @@ import org.springframework.scheduling.TaskScheduler;
 public class TcpInboundGatewaySpec extends MessagingGatewaySpec<TcpInboundGatewaySpec, TcpInboundGateway>
 		implements ComponentsRegistration {
 
-	private final AbstractConnectionFactory connectionFactory;
+	protected final AbstractConnectionFactory connectionFactory; // NOSONAR - final
 
 	/**
 	 * Construct an instance using an existing spring-managed connection factory.
 	 * @param connectionFactoryBean the spring-managed bean.
 	 */
-	TcpInboundGatewaySpec(AbstractConnectionFactory connectionFactoryBean) {
+	protected TcpInboundGatewaySpec(AbstractConnectionFactory connectionFactoryBean) {
 		super(new TcpInboundGateway());
 		this.connectionFactory = null;
 		this.target.setConnectionFactory(connectionFactoryBean);
@@ -53,7 +53,7 @@ public class TcpInboundGatewaySpec extends MessagingGatewaySpec<TcpInboundGatewa
 	 * Construct an instance using a connection factory spec.
 	 * @param connectionFactorySpec the spec.
 	 */
-	TcpInboundGatewaySpec(AbstractConnectionFactorySpec<?, ?> connectionFactorySpec) {
+	protected TcpInboundGatewaySpec(AbstractConnectionFactorySpec<?, ?> connectionFactorySpec) {
 		super(new TcpInboundGateway());
 		this.connectionFactory = connectionFactorySpec.get();
 		this.target.setConnectionFactory(this.connectionFactory);
diff --git a/spring-integration-ip/src/main/java/org/springframework/integration/ip/dsl/TcpOutboundChannelAdapterSpec.java b/spring-integration-ip/src/main/java/org/springframework/integration/ip/dsl/TcpOutboundChannelAdapterSpec.java
index 73776e30e8..211aa47ce0 100644
--- a/spring-integration-ip/src/main/java/org/springframework/integration/ip/dsl/TcpOutboundChannelAdapterSpec.java
+++ b/spring-integration-ip/src/main/java/org/springframework/integration/ip/dsl/TcpOutboundChannelAdapterSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -38,13 +38,13 @@ public class TcpOutboundChannelAdapterSpec
 		extends MessageHandlerSpec<TcpOutboundChannelAdapterSpec, TcpSendingMessageHandler>
 		implements ComponentsRegistration {
 
-	private final AbstractConnectionFactory connectionFactory;
+	protected final AbstractConnectionFactory connectionFactory; // NOSONAR - final
 
 	/**
 	 * Construct an instance using an existing spring-managed connection factory.
 	 * @param connectionFactoryBean the spring-managed bean.
 	 */
-	TcpOutboundChannelAdapterSpec(AbstractConnectionFactory connectionFactoryBean) {
+	protected TcpOutboundChannelAdapterSpec(AbstractConnectionFactory connectionFactoryBean) {
 		this.target = new TcpSendingMessageHandler();
 		this.connectionFactory = null;
 		this.target.setConnectionFactory(connectionFactoryBean);
@@ -54,7 +54,7 @@ public class TcpOutboundChannelAdapterSpec
 	 * Construct an instance using the provided connection factory spec.
 	 * @param connectionFactorySpec the spec.
 	 */
-	TcpOutboundChannelAdapterSpec(AbstractConnectionFactorySpec<?, ?> connectionFactorySpec) {
+	protected TcpOutboundChannelAdapterSpec(AbstractConnectionFactorySpec<?, ?> connectionFactorySpec) {
 		this.target = new TcpSendingMessageHandler();
 		this.connectionFactory = connectionFactorySpec.get();
 		this.target.setConnectionFactory(this.connectionFactory);
diff --git a/spring-integration-ip/src/main/java/org/springframework/integration/ip/dsl/TcpOutboundGatewaySpec.java b/spring-integration-ip/src/main/java/org/springframework/integration/ip/dsl/TcpOutboundGatewaySpec.java
index 87cbb0b922..9389ccdc2b 100644
--- a/spring-integration-ip/src/main/java/org/springframework/integration/ip/dsl/TcpOutboundGatewaySpec.java
+++ b/spring-integration-ip/src/main/java/org/springframework/integration/ip/dsl/TcpOutboundGatewaySpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -39,7 +39,7 @@ import org.springframework.messaging.Message;
 public class TcpOutboundGatewaySpec extends MessageHandlerSpec<TcpOutboundGatewaySpec, TcpOutboundGateway>
 		implements ComponentsRegistration {
 
-	private final AbstractClientConnectionFactory connectionFactory;
+	protected final AbstractClientConnectionFactory connectionFactory; // NOSONAR - final
 
 	/**
 	 * Construct an instance using an existing spring-managed connection factory.
diff --git a/spring-integration-ip/src/main/java/org/springframework/integration/ip/dsl/TcpServerConnectionFactorySpec.java b/spring-integration-ip/src/main/java/org/springframework/integration/ip/dsl/TcpServerConnectionFactorySpec.java
index 1f83077266..2e540cbb08 100644
--- a/spring-integration-ip/src/main/java/org/springframework/integration/ip/dsl/TcpServerConnectionFactorySpec.java
+++ b/spring-integration-ip/src/main/java/org/springframework/integration/ip/dsl/TcpServerConnectionFactorySpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -22,7 +22,9 @@ import org.springframework.integration.ip.tcp.connection.TcpNioServerConnectionF
 
 /**
  * An {@link AbstractConnectionFactorySpec} for {@link AbstractServerConnectionFactory}s.
+ *
  * @author Gary Russell
+ * @author Artem Bilan
  *
  * @since 5.0
  *
@@ -30,11 +32,11 @@ import org.springframework.integration.ip.tcp.connection.TcpNioServerConnectionF
 public class TcpServerConnectionFactorySpec
 		extends AbstractConnectionFactorySpec<TcpServerConnectionFactorySpec, AbstractServerConnectionFactory> {
 
-	TcpServerConnectionFactorySpec(int port) {
+	protected TcpServerConnectionFactorySpec(int port) {
 		this(port, false);
 	}
 
-	TcpServerConnectionFactorySpec(int port, boolean nio) {
+	protected TcpServerConnectionFactorySpec(int port, boolean nio) {
 		super(nio ? new TcpNioServerConnectionFactory(port) : new TcpNetServerConnectionFactory(port));
 	}
 
diff --git a/spring-integration-ip/src/main/java/org/springframework/integration/ip/dsl/UdpInboundChannelAdapterSpec.java b/spring-integration-ip/src/main/java/org/springframework/integration/ip/dsl/UdpInboundChannelAdapterSpec.java
index c43781f3bb..009f3926c5 100644
--- a/spring-integration-ip/src/main/java/org/springframework/integration/ip/dsl/UdpInboundChannelAdapterSpec.java
+++ b/spring-integration-ip/src/main/java/org/springframework/integration/ip/dsl/UdpInboundChannelAdapterSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -28,17 +28,18 @@ import org.springframework.scheduling.TaskScheduler;
  * A {@link MessageProducerSpec} for {@link UnicastReceivingChannelAdapter}s.
  *
  * @author Gary Russell
+ *
  * @since 5.0
  *
  */
 public class UdpInboundChannelAdapterSpec
 		extends MessageProducerSpec<UdpInboundChannelAdapterSpec, UnicastReceivingChannelAdapter> {
 
-	UdpInboundChannelAdapterSpec(int port) {
+	protected UdpInboundChannelAdapterSpec(int port) {
 		super(new UnicastReceivingChannelAdapter(port));
 	}
 
-	UdpInboundChannelAdapterSpec(int port, String multicastGroup) {
+	protected UdpInboundChannelAdapterSpec(int port, String multicastGroup) {
 		super(new MulticastReceivingChannelAdapter(multicastGroup, port));
 	}
 
diff --git a/spring-integration-ip/src/main/java/org/springframework/integration/ip/dsl/UdpMulticastOutboundChannelAdapterSpec.java b/spring-integration-ip/src/main/java/org/springframework/integration/ip/dsl/UdpMulticastOutboundChannelAdapterSpec.java
index 05b3aab858..58f69d1bdc 100644
--- a/spring-integration-ip/src/main/java/org/springframework/integration/ip/dsl/UdpMulticastOutboundChannelAdapterSpec.java
+++ b/spring-integration-ip/src/main/java/org/springframework/integration/ip/dsl/UdpMulticastOutboundChannelAdapterSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -27,21 +27,23 @@ import org.springframework.messaging.Message;
  * {@link MulticastSendingMessageHandler}s.
  *
  * @author Gary Russell
+ * @author Artem Bilan
+ *
  * @since 5.0
  *
  */
 public class UdpMulticastOutboundChannelAdapterSpec
 		extends AbstractUdpOutboundChannelAdapterSpec<UdpMulticastOutboundChannelAdapterSpec> {
 
-	UdpMulticastOutboundChannelAdapterSpec(String host, int port) {
+	protected UdpMulticastOutboundChannelAdapterSpec(String host, int port) {
 		this.target = new MulticastSendingMessageHandler(host, port);
 	}
 
-	UdpMulticastOutboundChannelAdapterSpec(String destinationExpression) {
+	protected UdpMulticastOutboundChannelAdapterSpec(String destinationExpression) {
 		this.target = new MulticastSendingMessageHandler(destinationExpression);
 	}
 
-	UdpMulticastOutboundChannelAdapterSpec(Function<Message<?>, ?> destinationFunction) {
+	protected UdpMulticastOutboundChannelAdapterSpec(Function<Message<?>, ?> destinationFunction) {
 		this.target = new MulticastSendingMessageHandler(new FunctionExpression<>(destinationFunction));
 	}
 
diff --git a/spring-integration-ip/src/main/java/org/springframework/integration/ip/dsl/UdpUnicastOutboundChannelAdapterSpec.java b/spring-integration-ip/src/main/java/org/springframework/integration/ip/dsl/UdpUnicastOutboundChannelAdapterSpec.java
index 81d7a3f699..ed14579d0e 100644
--- a/spring-integration-ip/src/main/java/org/springframework/integration/ip/dsl/UdpUnicastOutboundChannelAdapterSpec.java
+++ b/spring-integration-ip/src/main/java/org/springframework/integration/ip/dsl/UdpUnicastOutboundChannelAdapterSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -25,21 +25,23 @@ import org.springframework.messaging.Message;
  * {@link org.springframework.integration.ip.udp.UnicastSendingMessageHandler}s.
  *
  * @author Gary Russell
+ * @author Artem Bilan
+ *
  * @since 5.0
  *
  */
 public class UdpUnicastOutboundChannelAdapterSpec
 		extends AbstractUdpOutboundChannelAdapterSpec<UdpUnicastOutboundChannelAdapterSpec> {
 
-	UdpUnicastOutboundChannelAdapterSpec(String host, int port) {
+	protected UdpUnicastOutboundChannelAdapterSpec(String host, int port) {
 		super(host, port);
 	}
 
-	UdpUnicastOutboundChannelAdapterSpec(Function<Message<?>, ?> destinationFunction) {
+	protected UdpUnicastOutboundChannelAdapterSpec(Function<Message<?>, ?> destinationFunction) {
 		super(destinationFunction);
 	}
 
-	UdpUnicastOutboundChannelAdapterSpec(String destinationExpression) {
+	protected UdpUnicastOutboundChannelAdapterSpec(String destinationExpression) {
 		super(destinationExpression);
 	}
 
diff --git a/spring-integration-jms/src/main/java/org/springframework/integration/jms/dsl/JmsDefaultListenerContainerSpec.java b/spring-integration-jms/src/main/java/org/springframework/integration/jms/dsl/JmsDefaultListenerContainerSpec.java
index 97ef6c69db..4139b48e07 100644
--- a/spring-integration-jms/src/main/java/org/springframework/integration/jms/dsl/JmsDefaultListenerContainerSpec.java
+++ b/spring-integration-jms/src/main/java/org/springframework/integration/jms/dsl/JmsDefaultListenerContainerSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -31,7 +31,7 @@ import org.springframework.util.backoff.BackOff;
 public class JmsDefaultListenerContainerSpec
 		extends JmsListenerContainerSpec<JmsDefaultListenerContainerSpec, DefaultMessageListenerContainer> {
 
-	JmsDefaultListenerContainerSpec() {
+	protected JmsDefaultListenerContainerSpec() {
 		super(DefaultMessageListenerContainer.class);
 	}
 
diff --git a/spring-integration-jms/src/main/java/org/springframework/integration/jms/dsl/JmsDestinationAccessorSpec.java b/spring-integration-jms/src/main/java/org/springframework/integration/jms/dsl/JmsDestinationAccessorSpec.java
index 543e825875..58778b4480 100644
--- a/spring-integration-jms/src/main/java/org/springframework/integration/jms/dsl/JmsDestinationAccessorSpec.java
+++ b/spring-integration-jms/src/main/java/org/springframework/integration/jms/dsl/JmsDestinationAccessorSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -39,7 +39,7 @@ public abstract class JmsDestinationAccessorSpec<S extends JmsDestinationAccesso
 		this.target = accessor;
 	}
 
-	S connectionFactory(ConnectionFactory connectionFactory) {
+	protected S connectionFactory(ConnectionFactory connectionFactory) {
 		this.target.setConnectionFactory(connectionFactory);
 		return _this();
 	}
diff --git a/spring-integration-jms/src/main/java/org/springframework/integration/jms/dsl/JmsInboundChannelAdapterSpec.java b/spring-integration-jms/src/main/java/org/springframework/integration/jms/dsl/JmsInboundChannelAdapterSpec.java
index f814a9a8c2..c6a38b3bc8 100644
--- a/spring-integration-jms/src/main/java/org/springframework/integration/jms/dsl/JmsInboundChannelAdapterSpec.java
+++ b/spring-integration-jms/src/main/java/org/springframework/integration/jms/dsl/JmsInboundChannelAdapterSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -44,7 +44,7 @@ public class JmsInboundChannelAdapterSpec<S extends JmsInboundChannelAdapterSpec
 
 	protected final JmsTemplateSpec jmsTemplateSpec = new JmsTemplateSpec(); // NOSONAR final
 
-	JmsInboundChannelAdapterSpec(JmsTemplate jmsTemplate) {
+	protected JmsInboundChannelAdapterSpec(JmsTemplate jmsTemplate) {
 		this.target = new JmsDestinationPollingSource(jmsTemplate);
 	}
 
@@ -100,7 +100,7 @@ public class JmsInboundChannelAdapterSpec<S extends JmsInboundChannelAdapterSpec
 			extends JmsInboundChannelAdapterSpec<JmsInboundChannelSpecTemplateAware>
 			implements ComponentsRegistration {
 
-		JmsInboundChannelSpecTemplateAware(ConnectionFactory connectionFactory) {
+		protected JmsInboundChannelSpecTemplateAware(ConnectionFactory connectionFactory) {
 			super(connectionFactory);
 		}
 
diff --git a/spring-integration-jms/src/main/java/org/springframework/integration/jms/dsl/JmsInboundGatewaySpec.java b/spring-integration-jms/src/main/java/org/springframework/integration/jms/dsl/JmsInboundGatewaySpec.java
index 14cca1d9a0..bf824be77b 100644
--- a/spring-integration-jms/src/main/java/org/springframework/integration/jms/dsl/JmsInboundGatewaySpec.java
+++ b/spring-integration-jms/src/main/java/org/springframework/integration/jms/dsl/JmsInboundGatewaySpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -42,7 +42,7 @@ import org.springframework.util.Assert;
 public class JmsInboundGatewaySpec<S extends JmsInboundGatewaySpec<S>>
 		extends MessagingGatewaySpec<S, JmsInboundGateway> {
 
-	JmsInboundGatewaySpec(AbstractMessageListenerContainer listenerContainer) {
+	protected JmsInboundGatewaySpec(AbstractMessageListenerContainer listenerContainer) {
 		super(new JmsInboundGateway(listenerContainer, new ChannelPublishingJmsMessageListener()));
 		this.target.getListener().setExpectReply(true);
 	}
@@ -202,7 +202,7 @@ public class JmsInboundGatewaySpec<S extends JmsInboundGatewaySpec<S>>
 
 		private final S spec;
 
-		JmsInboundGatewayListenerContainerSpec(S spec) {
+		protected JmsInboundGatewayListenerContainerSpec(S spec) {
 			super(spec.get());
 			this.spec = spec;
 			this.spec.get().setAutoStartup(false);
diff --git a/spring-integration-jms/src/main/java/org/springframework/integration/jms/dsl/JmsListenerContainerSpec.java b/spring-integration-jms/src/main/java/org/springframework/integration/jms/dsl/JmsListenerContainerSpec.java
index 1ca0bf0267..ccf67919e7 100644
--- a/spring-integration-jms/src/main/java/org/springframework/integration/jms/dsl/JmsListenerContainerSpec.java
+++ b/spring-integration-jms/src/main/java/org/springframework/integration/jms/dsl/JmsListenerContainerSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -37,7 +37,7 @@ import org.springframework.util.ErrorHandler;
 public class JmsListenerContainerSpec<S extends JmsListenerContainerSpec<S, C>, C extends AbstractMessageListenerContainer>
 		extends JmsDestinationAccessorSpec<S, C> {
 
-	JmsListenerContainerSpec(Class<C> aClass) {
+	protected JmsListenerContainerSpec(Class<C> aClass) {
 		super(newInstance(aClass));
 		if (DefaultMessageListenerContainer.class.isAssignableFrom(aClass)) {
 			this.target.setSessionTransacted(true);
diff --git a/spring-integration-jms/src/main/java/org/springframework/integration/jms/dsl/JmsMessageChannelSpec.java b/spring-integration-jms/src/main/java/org/springframework/integration/jms/dsl/JmsMessageChannelSpec.java
index c32a63752a..6a8af37a0c 100644
--- a/spring-integration-jms/src/main/java/org/springframework/integration/jms/dsl/JmsMessageChannelSpec.java
+++ b/spring-integration-jms/src/main/java/org/springframework/integration/jms/dsl/JmsMessageChannelSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -37,7 +37,7 @@ import org.springframework.util.ErrorHandler;
  */
 public class JmsMessageChannelSpec<S extends JmsMessageChannelSpec<S>> extends JmsPollableMessageChannelSpec<S> {
 
-	JmsMessageChannelSpec(ConnectionFactory connectionFactory) {
+	protected JmsMessageChannelSpec(ConnectionFactory connectionFactory) {
 		super(new JmsChannelFactoryBean(true), connectionFactory);
 	}
 
diff --git a/spring-integration-jms/src/main/java/org/springframework/integration/jms/dsl/JmsMessageDrivenChannelAdapterSpec.java b/spring-integration-jms/src/main/java/org/springframework/integration/jms/dsl/JmsMessageDrivenChannelAdapterSpec.java
index ce4452bbd6..295b5ac6b9 100644
--- a/spring-integration-jms/src/main/java/org/springframework/integration/jms/dsl/JmsMessageDrivenChannelAdapterSpec.java
+++ b/spring-integration-jms/src/main/java/org/springframework/integration/jms/dsl/JmsMessageDrivenChannelAdapterSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -44,7 +44,7 @@ import org.springframework.util.Assert;
 public class JmsMessageDrivenChannelAdapterSpec<S extends JmsMessageDrivenChannelAdapterSpec<S>>
 		extends MessageProducerSpec<S, JmsMessageDrivenEndpoint> {
 
-	JmsMessageDrivenChannelAdapterSpec(AbstractMessageListenerContainer listenerContainer) {
+	protected JmsMessageDrivenChannelAdapterSpec(AbstractMessageListenerContainer listenerContainer) {
 		super(new JmsMessageDrivenEndpoint(listenerContainer, new ChannelPublishingJmsMessageListener()));
 		this.target.getListener().setExpectReply(false);
 	}
@@ -105,7 +105,7 @@ public class JmsMessageDrivenChannelAdapterSpec<S extends JmsMessageDrivenChanne
 
 		private final S spec;
 
-		JmsMessageDrivenChannelAdapterListenerContainerSpec(S spec) {
+		protected JmsMessageDrivenChannelAdapterListenerContainerSpec(S spec) {
 			super(spec.get());
 			this.spec = spec;
 			this.spec.get().setAutoStartup(false);
diff --git a/spring-integration-jms/src/main/java/org/springframework/integration/jms/dsl/JmsOutboundChannelAdapterSpec.java b/spring-integration-jms/src/main/java/org/springframework/integration/jms/dsl/JmsOutboundChannelAdapterSpec.java
index c2732458e7..b44a6e1d5c 100644
--- a/spring-integration-jms/src/main/java/org/springframework/integration/jms/dsl/JmsOutboundChannelAdapterSpec.java
+++ b/spring-integration-jms/src/main/java/org/springframework/integration/jms/dsl/JmsOutboundChannelAdapterSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -46,7 +46,7 @@ public class JmsOutboundChannelAdapterSpec<S extends JmsOutboundChannelAdapterSp
 
 	protected final JmsTemplateSpec jmsTemplateSpec = new JmsTemplateSpec(); // NOSONAR final
 
-	JmsOutboundChannelAdapterSpec(JmsTemplate jmsTemplate) {
+	protected JmsOutboundChannelAdapterSpec(JmsTemplate jmsTemplate) {
 		this.target = new JmsSendingMessageHandler(jmsTemplate);
 	}
 
@@ -182,7 +182,7 @@ public class JmsOutboundChannelAdapterSpec<S extends JmsOutboundChannelAdapterSp
 			extends JmsOutboundChannelAdapterSpec<JmsOutboundChannelSpecTemplateAware>
 			implements ComponentsRegistration {
 
-		JmsOutboundChannelSpecTemplateAware(ConnectionFactory connectionFactory) {
+		protected JmsOutboundChannelSpecTemplateAware(ConnectionFactory connectionFactory) {
 			super(connectionFactory);
 		}
 
diff --git a/spring-integration-jms/src/main/java/org/springframework/integration/jms/dsl/JmsOutboundGatewaySpec.java b/spring-integration-jms/src/main/java/org/springframework/integration/jms/dsl/JmsOutboundGatewaySpec.java
index 452c869a41..7df015b72a 100644
--- a/spring-integration-jms/src/main/java/org/springframework/integration/jms/dsl/JmsOutboundGatewaySpec.java
+++ b/spring-integration-jms/src/main/java/org/springframework/integration/jms/dsl/JmsOutboundGatewaySpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -41,7 +41,7 @@ import org.springframework.util.Assert;
  */
 public class JmsOutboundGatewaySpec extends MessageHandlerSpec<JmsOutboundGatewaySpec, JmsOutboundGateway> {
 
-	JmsOutboundGatewaySpec(ConnectionFactory connectionFactory) {
+	protected JmsOutboundGatewaySpec(ConnectionFactory connectionFactory) {
 		this.target = new JmsOutboundGateway();
 		this.target.setConnectionFactory(connectionFactory);
 		this.target.setRequiresReply(true);
diff --git a/spring-integration-jms/src/main/java/org/springframework/integration/jms/dsl/JmsPollableMessageChannelSpec.java b/spring-integration-jms/src/main/java/org/springframework/integration/jms/dsl/JmsPollableMessageChannelSpec.java
index e9884ff73a..9b5fb36c81 100644
--- a/spring-integration-jms/src/main/java/org/springframework/integration/jms/dsl/JmsPollableMessageChannelSpec.java
+++ b/spring-integration-jms/src/main/java/org/springframework/integration/jms/dsl/JmsPollableMessageChannelSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -41,13 +41,15 @@ import org.springframework.lang.Nullable;
 public class JmsPollableMessageChannelSpec<S extends JmsPollableMessageChannelSpec<S>>
 		extends MessageChannelSpec<S, AbstractJmsChannel> {
 
-	protected final JmsChannelFactoryBean jmsChannelFactoryBean; // NOSONAR final
+	protected final JmsChannelFactoryBean jmsChannelFactoryBean; // NOSONAR - final
 
-	JmsPollableMessageChannelSpec(ConnectionFactory connectionFactory) {
+	protected JmsPollableMessageChannelSpec(ConnectionFactory connectionFactory) {
 		this(new JmsChannelFactoryBean(false), connectionFactory);
 	}
 
-	JmsPollableMessageChannelSpec(JmsChannelFactoryBean jmsChannelFactoryBean, ConnectionFactory connectionFactory) {
+	protected JmsPollableMessageChannelSpec(JmsChannelFactoryBean jmsChannelFactoryBean,
+			ConnectionFactory connectionFactory) {
+
 		this.jmsChannelFactoryBean = jmsChannelFactoryBean;
 		this.jmsChannelFactoryBean.setConnectionFactory(connectionFactory);
 		this.jmsChannelFactoryBean.setSingleton(false);
@@ -95,9 +97,8 @@ public class JmsPollableMessageChannelSpec<S extends JmsPollableMessageChannelSp
 
 	/**
 	 * Configure a message selector in the
-	 * {@link org.springframework.jms.listener.DefaultMessageListenerContainer} (when
-	 * message driven) or the {@link org.springframework.jms.core.JmsTemplate} (when
-	 * polled).
+	 * {@link org.springframework.jms.listener.DefaultMessageListenerContainer} (when message driven)
+	 * or the {@link org.springframework.jms.core.JmsTemplate} (when polled).
 	 * @param messageSelector the messageSelector.
 	 * @return the current {@link MessageChannelSpec}.
 	 * @see org.springframework.jms.listener.DefaultMessageListenerContainer#setMessageSelector(String)
diff --git a/spring-integration-jms/src/main/java/org/springframework/integration/jms/dsl/JmsPublishSubscribeMessageChannelSpec.java b/spring-integration-jms/src/main/java/org/springframework/integration/jms/dsl/JmsPublishSubscribeMessageChannelSpec.java
index f1fb93a336..a71b1f31f3 100644
--- a/spring-integration-jms/src/main/java/org/springframework/integration/jms/dsl/JmsPublishSubscribeMessageChannelSpec.java
+++ b/spring-integration-jms/src/main/java/org/springframework/integration/jms/dsl/JmsPublishSubscribeMessageChannelSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -28,7 +28,7 @@ import javax.jms.ConnectionFactory;
 public class JmsPublishSubscribeMessageChannelSpec
 		extends JmsMessageChannelSpec<JmsPublishSubscribeMessageChannelSpec> {
 
-	JmsPublishSubscribeMessageChannelSpec(ConnectionFactory connectionFactory) {
+	protected JmsPublishSubscribeMessageChannelSpec(ConnectionFactory connectionFactory) {
 		super(connectionFactory);
 		this.jmsChannelFactoryBean.setPubSubDomain(true);
 	}
diff --git a/spring-integration-jms/src/main/java/org/springframework/integration/jms/dsl/JmsTemplateSpec.java b/spring-integration-jms/src/main/java/org/springframework/integration/jms/dsl/JmsTemplateSpec.java
index 6e5c73353d..026472a317 100644
--- a/spring-integration-jms/src/main/java/org/springframework/integration/jms/dsl/JmsTemplateSpec.java
+++ b/spring-integration-jms/src/main/java/org/springframework/integration/jms/dsl/JmsTemplateSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -27,7 +27,7 @@ import org.springframework.jms.support.converter.MessageConverter;
  */
 public class JmsTemplateSpec extends JmsDestinationAccessorSpec<JmsTemplateSpec, DynamicJmsTemplate> {
 
-	JmsTemplateSpec() {
+	protected JmsTemplateSpec() {
 		super(new DynamicJmsTemplate());
 	}
 
diff --git a/spring-integration-jpa/src/main/java/org/springframework/integration/jpa/dsl/JpaInboundChannelAdapterSpec.java b/spring-integration-jpa/src/main/java/org/springframework/integration/jpa/dsl/JpaInboundChannelAdapterSpec.java
index 81bdeafbf4..d2592e8697 100644
--- a/spring-integration-jpa/src/main/java/org/springframework/integration/jpa/dsl/JpaInboundChannelAdapterSpec.java
+++ b/spring-integration-jpa/src/main/java/org/springframework/integration/jpa/dsl/JpaInboundChannelAdapterSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -38,9 +38,9 @@ public class JpaInboundChannelAdapterSpec
 		extends MessageSourceSpec<JpaInboundChannelAdapterSpec, JpaPollingChannelAdapter>
 		implements ComponentsRegistration {
 
-	private final JpaExecutor jpaExecutor;
+	protected final JpaExecutor jpaExecutor; // NOSONAR - final
 
-	JpaInboundChannelAdapterSpec(JpaExecutor jpaExecutor) {
+	protected JpaInboundChannelAdapterSpec(JpaExecutor jpaExecutor) {
 		this.jpaExecutor = jpaExecutor;
 		this.target = new JpaPollingChannelAdapter(this.jpaExecutor);
 	}
diff --git a/spring-integration-jpa/src/main/java/org/springframework/integration/jpa/dsl/JpaRetrievingOutboundGatewaySpec.java b/spring-integration-jpa/src/main/java/org/springframework/integration/jpa/dsl/JpaRetrievingOutboundGatewaySpec.java
index 02d803db34..c2ce78f5ca 100644
--- a/spring-integration-jpa/src/main/java/org/springframework/integration/jpa/dsl/JpaRetrievingOutboundGatewaySpec.java
+++ b/spring-integration-jpa/src/main/java/org/springframework/integration/jpa/dsl/JpaRetrievingOutboundGatewaySpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -32,7 +32,7 @@ import org.springframework.integration.jpa.support.OutboundGatewayType;
  */
 public class JpaRetrievingOutboundGatewaySpec extends JpaBaseOutboundEndpointSpec<JpaRetrievingOutboundGatewaySpec> {
 
-	JpaRetrievingOutboundGatewaySpec(JpaExecutor jpaExecutor) {
+	protected JpaRetrievingOutboundGatewaySpec(JpaExecutor jpaExecutor) {
 		super(jpaExecutor);
 		this.target.setGatewayType(OutboundGatewayType.RETRIEVING);
 		this.target.setRequiresReply(true);
diff --git a/spring-integration-jpa/src/main/java/org/springframework/integration/jpa/dsl/JpaUpdatingOutboundEndpointSpec.java b/spring-integration-jpa/src/main/java/org/springframework/integration/jpa/dsl/JpaUpdatingOutboundEndpointSpec.java
index 784127b751..ef6ce62766 100644
--- a/spring-integration-jpa/src/main/java/org/springframework/integration/jpa/dsl/JpaUpdatingOutboundEndpointSpec.java
+++ b/spring-integration-jpa/src/main/java/org/springframework/integration/jpa/dsl/JpaUpdatingOutboundEndpointSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -30,11 +30,11 @@ import org.springframework.integration.jpa.support.PersistMode;
  */
 public class JpaUpdatingOutboundEndpointSpec extends JpaBaseOutboundEndpointSpec<JpaUpdatingOutboundEndpointSpec> {
 
-	JpaUpdatingOutboundEndpointSpec(JpaExecutor jpaExecutor) {
+	protected JpaUpdatingOutboundEndpointSpec(JpaExecutor jpaExecutor) {
 		super(jpaExecutor);
 	}
 
-	JpaUpdatingOutboundEndpointSpec producesReply(boolean producesReply) {
+	protected JpaUpdatingOutboundEndpointSpec producesReply(boolean producesReply) {
 		this.target.setProducesReply(producesReply);
 		if (producesReply) {
 			this.target.setRequiresReply(true);
diff --git a/spring-integration-mail/src/main/java/org/springframework/integration/mail/dsl/ImapIdleChannelAdapterSpec.java b/spring-integration-mail/src/main/java/org/springframework/integration/mail/dsl/ImapIdleChannelAdapterSpec.java
index d61ceccb5e..eb04fc7667 100644
--- a/spring-integration-mail/src/main/java/org/springframework/integration/mail/dsl/ImapIdleChannelAdapterSpec.java
+++ b/spring-integration-mail/src/main/java/org/springframework/integration/mail/dsl/ImapIdleChannelAdapterSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2014-2019 the original author or authors.
+ * Copyright 2014-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -59,9 +59,9 @@ public class ImapIdleChannelAdapterSpec
 		extends MessageProducerSpec<ImapIdleChannelAdapterSpec, ImapIdleChannelAdapter>
 		implements ComponentsRegistration {
 
-	private final ImapMailReceiver receiver;
+	protected final ImapMailReceiver receiver; // NOSONAR - final
 
-	private final Map<Object, String> componentsToRegister = new LinkedHashMap<>();
+	protected final Map<Object, String> componentsToRegister = new LinkedHashMap<>();  // NOSONAR - final
 
 	private final List<Advice> adviceChain = new LinkedList<>();
 
@@ -69,11 +69,11 @@ public class ImapIdleChannelAdapterSpec
 
 	private boolean sessionProvided;
 
-	ImapIdleChannelAdapterSpec(ImapMailReceiver receiver) {
+	protected ImapIdleChannelAdapterSpec(ImapMailReceiver receiver) {
 		this(receiver, false);
 	}
 
-	ImapIdleChannelAdapterSpec(ImapMailReceiver receiver, boolean externalReceiver) {
+	protected ImapIdleChannelAdapterSpec(ImapMailReceiver receiver, boolean externalReceiver) {
 		super(new ImapIdleChannelAdapter(receiver));
 		this.target.setAdviceChain(this.adviceChain);
 		this.receiver = receiver;
diff --git a/spring-integration-mail/src/main/java/org/springframework/integration/mail/dsl/ImapMailInboundChannelAdapterSpec.java b/spring-integration-mail/src/main/java/org/springframework/integration/mail/dsl/ImapMailInboundChannelAdapterSpec.java
index a09671d514..177aa307d5 100644
--- a/spring-integration-mail/src/main/java/org/springframework/integration/mail/dsl/ImapMailInboundChannelAdapterSpec.java
+++ b/spring-integration-mail/src/main/java/org/springframework/integration/mail/dsl/ImapMailInboundChannelAdapterSpec.java
@@ -30,15 +30,15 @@ import org.springframework.integration.mail.SearchTermStrategy;
 public class ImapMailInboundChannelAdapterSpec
 		extends MailInboundChannelAdapterSpec<ImapMailInboundChannelAdapterSpec, ImapMailReceiver> {
 
-	ImapMailInboundChannelAdapterSpec() {
+	protected ImapMailInboundChannelAdapterSpec() {
 		super(new ImapMailReceiver());
 	}
 
-	ImapMailInboundChannelAdapterSpec(ImapMailReceiver imapMailReceiver) {
+	protected ImapMailInboundChannelAdapterSpec(ImapMailReceiver imapMailReceiver) {
 		super(imapMailReceiver, true);
 	}
 
-	ImapMailInboundChannelAdapterSpec(String url) {
+	protected ImapMailInboundChannelAdapterSpec(String url) {
 		super(new ImapMailReceiver(url), false);
 	}
 
diff --git a/spring-integration-mail/src/main/java/org/springframework/integration/mail/dsl/MailSendingMessageHandlerSpec.java b/spring-integration-mail/src/main/java/org/springframework/integration/mail/dsl/MailSendingMessageHandlerSpec.java
index eaed04f181..14a2c7d0e9 100644
--- a/spring-integration-mail/src/main/java/org/springframework/integration/mail/dsl/MailSendingMessageHandlerSpec.java
+++ b/spring-integration-mail/src/main/java/org/springframework/integration/mail/dsl/MailSendingMessageHandlerSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2014-2019 the original author or authors.
+ * Copyright 2014-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -36,9 +36,9 @@ import org.springframework.mail.javamail.JavaMailSenderImpl;
 public class MailSendingMessageHandlerSpec
 		extends MessageHandlerSpec<MailSendingMessageHandlerSpec, MailSendingMessageHandler> {
 
-	private final JavaMailSenderImpl sender = new JavaMailSenderImpl();
+	protected final JavaMailSenderImpl sender = new JavaMailSenderImpl(); // NOSONAR - final
 
-	MailSendingMessageHandlerSpec(@Nullable String host) {
+	protected MailSendingMessageHandlerSpec(@Nullable String host) {
 		this.sender.setHost(host);
 		this.target = new MailSendingMessageHandler(this.sender);
 	}
diff --git a/spring-integration-mail/src/main/java/org/springframework/integration/mail/dsl/Pop3MailInboundChannelAdapterSpec.java b/spring-integration-mail/src/main/java/org/springframework/integration/mail/dsl/Pop3MailInboundChannelAdapterSpec.java
index 70daf6348d..c0eadcf4a5 100644
--- a/spring-integration-mail/src/main/java/org/springframework/integration/mail/dsl/Pop3MailInboundChannelAdapterSpec.java
+++ b/spring-integration-mail/src/main/java/org/springframework/integration/mail/dsl/Pop3MailInboundChannelAdapterSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2014-2019 the original author or authors.
+ * Copyright 2014-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -28,23 +28,23 @@ import org.springframework.integration.mail.Pop3MailReceiver;
 public class Pop3MailInboundChannelAdapterSpec
 		extends MailInboundChannelAdapterSpec<Pop3MailInboundChannelAdapterSpec, Pop3MailReceiver> {
 
-	Pop3MailInboundChannelAdapterSpec() {
+	protected Pop3MailInboundChannelAdapterSpec() {
 		super(new Pop3MailReceiver());
 	}
 
-	Pop3MailInboundChannelAdapterSpec(Pop3MailReceiver receiver) {
+	protected Pop3MailInboundChannelAdapterSpec(Pop3MailReceiver receiver) {
 		super(receiver, true);
 	}
 
-	Pop3MailInboundChannelAdapterSpec(String url) {
+	protected Pop3MailInboundChannelAdapterSpec(String url) {
 		super(new Pop3MailReceiver(url));
 	}
 
-	Pop3MailInboundChannelAdapterSpec(String host, String username, String password) {
+	protected Pop3MailInboundChannelAdapterSpec(String host, String username, String password) {
 		super(new Pop3MailReceiver(host, username, password));
 	}
 
-	Pop3MailInboundChannelAdapterSpec(String host, int port, String username, String password) {
+	protected Pop3MailInboundChannelAdapterSpec(String host, int port, String username, String password) {
 		super(new Pop3MailReceiver(host, port, username, password));
 	}
 
diff --git a/spring-integration-mongodb/src/main/java/org/springframework/integration/mongodb/dsl/MongoDbOutboundGatewaySpec.java b/spring-integration-mongodb/src/main/java/org/springframework/integration/mongodb/dsl/MongoDbOutboundGatewaySpec.java
index 4658f53673..ff59898a34 100644
--- a/spring-integration-mongodb/src/main/java/org/springframework/integration/mongodb/dsl/MongoDbOutboundGatewaySpec.java
+++ b/spring-integration-mongodb/src/main/java/org/springframework/integration/mongodb/dsl/MongoDbOutboundGatewaySpec.java
@@ -40,12 +40,12 @@ import org.springframework.messaging.Message;
 public class MongoDbOutboundGatewaySpec
 		extends MessageHandlerSpec<MongoDbOutboundGatewaySpec, MongoDbOutboundGateway> {
 
-	MongoDbOutboundGatewaySpec(MongoDatabaseFactory mongoDbFactory, MongoConverter mongoConverter) {
+	protected MongoDbOutboundGatewaySpec(MongoDatabaseFactory mongoDbFactory, MongoConverter mongoConverter) {
 		this.target = new MongoDbOutboundGateway(mongoDbFactory, mongoConverter);
 		this.target.setRequiresReply(true);
 	}
 
-	MongoDbOutboundGatewaySpec(MongoOperations mongoTemplate) {
+	protected MongoDbOutboundGatewaySpec(MongoOperations mongoTemplate) {
 		this.target = new MongoDbOutboundGateway(mongoTemplate);
 		this.target.setRequiresReply(true);
 	}
diff --git a/spring-integration-mongodb/src/main/java/org/springframework/integration/mongodb/dsl/ReactiveMongoDbMessageHandlerSpec.java b/spring-integration-mongodb/src/main/java/org/springframework/integration/mongodb/dsl/ReactiveMongoDbMessageHandlerSpec.java
index f5fbb5dda8..f4ab5e64db 100644
--- a/spring-integration-mongodb/src/main/java/org/springframework/integration/mongodb/dsl/ReactiveMongoDbMessageHandlerSpec.java
+++ b/spring-integration-mongodb/src/main/java/org/springframework/integration/mongodb/dsl/ReactiveMongoDbMessageHandlerSpec.java
@@ -44,13 +44,13 @@ public class ReactiveMongoDbMessageHandlerSpec
 		extends MessageHandlerSpec<ReactiveMongoDbMessageHandlerSpec, ReactiveMessageHandlerAdapter>
 		implements ComponentsRegistration {
 
-	private final ReactiveMongoDbStoringMessageHandler messageHandler;
+	protected final ReactiveMongoDbStoringMessageHandler messageHandler; // NOSONAR - final
 
-	ReactiveMongoDbMessageHandlerSpec(ReactiveMongoDatabaseFactory mongoDbFactory) {
+	protected ReactiveMongoDbMessageHandlerSpec(ReactiveMongoDatabaseFactory mongoDbFactory) {
 		this(new ReactiveMongoDbStoringMessageHandler(mongoDbFactory));
 	}
 
-	ReactiveMongoDbMessageHandlerSpec(ReactiveMongoOperations reactiveMongoOperations) {
+	protected ReactiveMongoDbMessageHandlerSpec(ReactiveMongoOperations reactiveMongoOperations) {
 		this(new ReactiveMongoDbStoringMessageHandler(reactiveMongoOperations));
 	}
 
diff --git a/spring-integration-mongodb/src/main/java/org/springframework/integration/mongodb/dsl/ReactiveMongoDbMessageSourceSpec.java b/spring-integration-mongodb/src/main/java/org/springframework/integration/mongodb/dsl/ReactiveMongoDbMessageSourceSpec.java
index 59eb8c3718..174686fc56 100644
--- a/spring-integration-mongodb/src/main/java/org/springframework/integration/mongodb/dsl/ReactiveMongoDbMessageSourceSpec.java
+++ b/spring-integration-mongodb/src/main/java/org/springframework/integration/mongodb/dsl/ReactiveMongoDbMessageSourceSpec.java
@@ -37,12 +37,15 @@ import org.springframework.integration.mongodb.inbound.ReactiveMongoDbMessageSou
 public class ReactiveMongoDbMessageSourceSpec
 		extends MessageSourceSpec<ReactiveMongoDbMessageSourceSpec, ReactiveMongoDbMessageSource> {
 
-	ReactiveMongoDbMessageSourceSpec(ReactiveMongoDatabaseFactory reactiveMongoDatabaseFactory,
+	protected ReactiveMongoDbMessageSourceSpec(ReactiveMongoDatabaseFactory reactiveMongoDatabaseFactory,
 			Expression queryExpression) {
+
 		this.target = new ReactiveMongoDbMessageSource(reactiveMongoDatabaseFactory, queryExpression);
 	}
 
-	ReactiveMongoDbMessageSourceSpec(ReactiveMongoOperations reactiveMongoTemplate, Expression queryExpression) {
+	protected ReactiveMongoDbMessageSourceSpec(ReactiveMongoOperations reactiveMongoTemplate,
+			Expression queryExpression) {
+
 		this.target = new ReactiveMongoDbMessageSource(reactiveMongoTemplate, queryExpression);
 	}
 
diff --git a/spring-integration-rsocket/src/main/java/org/springframework/integration/rsocket/dsl/RSocketInboundGatewaySpec.java b/spring-integration-rsocket/src/main/java/org/springframework/integration/rsocket/dsl/RSocketInboundGatewaySpec.java
index b0a5d9566e..0c7cd14909 100644
--- a/spring-integration-rsocket/src/main/java/org/springframework/integration/rsocket/dsl/RSocketInboundGatewaySpec.java
+++ b/spring-integration-rsocket/src/main/java/org/springframework/integration/rsocket/dsl/RSocketInboundGatewaySpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2019 the original author or authors.
+ * Copyright 2019-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -32,7 +32,7 @@ import org.springframework.messaging.rsocket.RSocketStrategies;
  */
 public class RSocketInboundGatewaySpec extends MessagingGatewaySpec<RSocketInboundGatewaySpec, RSocketInboundGateway> {
 
-	RSocketInboundGatewaySpec(String... path) {
+	protected RSocketInboundGatewaySpec(String... path) {
 		super(new RSocketInboundGateway(path));
 	}
 
diff --git a/spring-integration-rsocket/src/main/java/org/springframework/integration/rsocket/dsl/RSocketOutboundGatewaySpec.java b/spring-integration-rsocket/src/main/java/org/springframework/integration/rsocket/dsl/RSocketOutboundGatewaySpec.java
index 4ad7b968b2..48bf76437c 100644
--- a/spring-integration-rsocket/src/main/java/org/springframework/integration/rsocket/dsl/RSocketOutboundGatewaySpec.java
+++ b/spring-integration-rsocket/src/main/java/org/springframework/integration/rsocket/dsl/RSocketOutboundGatewaySpec.java
@@ -38,11 +38,11 @@ import org.springframework.util.MimeType;
  */
 public class RSocketOutboundGatewaySpec extends MessageHandlerSpec<RSocketOutboundGatewaySpec, RSocketOutboundGateway> {
 
-	RSocketOutboundGatewaySpec(String route, Object... routeVariables) {
+	protected RSocketOutboundGatewaySpec(String route, Object... routeVariables) {
 		this.target = new RSocketOutboundGateway(route, routeVariables);
 	}
 
-	RSocketOutboundGatewaySpec(Expression routeExpression) {
+	protected RSocketOutboundGatewaySpec(Expression routeExpression) {
 		this.target = new RSocketOutboundGateway(routeExpression);
 	}
 
diff --git a/spring-integration-sftp/src/main/java/org/springframework/integration/sftp/dsl/SftpInboundChannelAdapterSpec.java b/spring-integration-sftp/src/main/java/org/springframework/integration/sftp/dsl/SftpInboundChannelAdapterSpec.java
index d7077fa155..38bf43647c 100644
--- a/spring-integration-sftp/src/main/java/org/springframework/integration/sftp/dsl/SftpInboundChannelAdapterSpec.java
+++ b/spring-integration-sftp/src/main/java/org/springframework/integration/sftp/dsl/SftpInboundChannelAdapterSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2014-2019 the original author or authors.
+ * Copyright 2014-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -42,7 +42,9 @@ public class SftpInboundChannelAdapterSpec
 		extends RemoteFileInboundChannelAdapterSpec<ChannelSftp.LsEntry, SftpInboundChannelAdapterSpec,
 				SftpInboundFileSynchronizingMessageSource> {
 
-	SftpInboundChannelAdapterSpec(SessionFactory<ChannelSftp.LsEntry> sessionFactory, Comparator<File> comparator) {
+	protected SftpInboundChannelAdapterSpec(SessionFactory<ChannelSftp.LsEntry> sessionFactory,
+			Comparator<File> comparator) {
+
 		super(new SftpInboundFileSynchronizer(sessionFactory));
 		this.target = new SftpInboundFileSynchronizingMessageSource(this.synchronizer, comparator);
 	}
diff --git a/spring-integration-sftp/src/main/java/org/springframework/integration/sftp/dsl/SftpMessageHandlerSpec.java b/spring-integration-sftp/src/main/java/org/springframework/integration/sftp/dsl/SftpMessageHandlerSpec.java
index e0d150fbfc..715b040b66 100644
--- a/spring-integration-sftp/src/main/java/org/springframework/integration/sftp/dsl/SftpMessageHandlerSpec.java
+++ b/spring-integration-sftp/src/main/java/org/springframework/integration/sftp/dsl/SftpMessageHandlerSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2014-2019 the original author or authors.
+ * Copyright 2014-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -34,16 +34,20 @@ import com.jcraft.jsch.ChannelSftp;
 public class SftpMessageHandlerSpec
 		extends FileTransferringMessageHandlerSpec<ChannelSftp.LsEntry, SftpMessageHandlerSpec> {
 
-	SftpMessageHandlerSpec(SessionFactory<ChannelSftp.LsEntry> sessionFactory) {
+	protected SftpMessageHandlerSpec(SessionFactory<ChannelSftp.LsEntry> sessionFactory) {
 		this.target = new SftpMessageHandler(sessionFactory);
 	}
 
-	SftpMessageHandlerSpec(RemoteFileTemplate<ChannelSftp.LsEntry> remoteFileTemplate) {
+	protected SftpMessageHandlerSpec(RemoteFileTemplate<ChannelSftp.LsEntry> remoteFileTemplate) {
 		this.target = new SftpMessageHandler(remoteFileTemplate.getSessionFactory());
 	}
 
-	SftpMessageHandlerSpec(RemoteFileTemplate<ChannelSftp.LsEntry> remoteFileTemplate, FileExistsMode fileExistsMode) {
-		this.target = new SftpMessageHandler(new SftpRemoteFileTemplate(remoteFileTemplate.getSessionFactory()), fileExistsMode);
+	protected SftpMessageHandlerSpec(RemoteFileTemplate<ChannelSftp.LsEntry> remoteFileTemplate,
+			FileExistsMode fileExistsMode) {
+
+		this.target =
+				new SftpMessageHandler(new SftpRemoteFileTemplate(remoteFileTemplate.getSessionFactory()),
+						fileExistsMode);
 	}
 
 }
diff --git a/spring-integration-sftp/src/main/java/org/springframework/integration/sftp/dsl/SftpOutboundGatewaySpec.java b/spring-integration-sftp/src/main/java/org/springframework/integration/sftp/dsl/SftpOutboundGatewaySpec.java
index e76ba25833..02df28e1f4 100644
--- a/spring-integration-sftp/src/main/java/org/springframework/integration/sftp/dsl/SftpOutboundGatewaySpec.java
+++ b/spring-integration-sftp/src/main/java/org/springframework/integration/sftp/dsl/SftpOutboundGatewaySpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2014-2019 the original author or authors.
+ * Copyright 2014-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -26,13 +26,14 @@ import com.jcraft.jsch.ChannelSftp;
 /**
  * @author Artem Bilan
  * @author Gary Russell
+ *
  * @since 5.0
  */
 public class SftpOutboundGatewaySpec
 		extends RemoteFileOutboundGatewaySpec<ChannelSftp.LsEntry, SftpOutboundGatewaySpec> {
 
 
-	SftpOutboundGatewaySpec(AbstractRemoteFileOutboundGateway<ChannelSftp.LsEntry> outboundGateway) {
+	protected SftpOutboundGatewaySpec(AbstractRemoteFileOutboundGateway<ChannelSftp.LsEntry> outboundGateway) {
 		super(outboundGateway);
 	}
 
diff --git a/spring-integration-sftp/src/main/java/org/springframework/integration/sftp/dsl/SftpStreamingInboundChannelAdapterSpec.java b/spring-integration-sftp/src/main/java/org/springframework/integration/sftp/dsl/SftpStreamingInboundChannelAdapterSpec.java
index 49856e4853..c12c71ca97 100644
--- a/spring-integration-sftp/src/main/java/org/springframework/integration/sftp/dsl/SftpStreamingInboundChannelAdapterSpec.java
+++ b/spring-integration-sftp/src/main/java/org/springframework/integration/sftp/dsl/SftpStreamingInboundChannelAdapterSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -32,6 +32,7 @@ import com.jcraft.jsch.ChannelSftp.LsEntry;
 
 /**
  * @author Gary Russell
+ *
  * @since 5.0
  *
  */
@@ -39,8 +40,9 @@ public class SftpStreamingInboundChannelAdapterSpec
 		extends RemoteFileStreamingInboundChannelAdapterSpec<LsEntry, SftpStreamingInboundChannelAdapterSpec,
 		SftpStreamingMessageSource> {
 
-	SftpStreamingInboundChannelAdapterSpec(RemoteFileTemplate<LsEntry> remoteFileTemplate,
+	protected SftpStreamingInboundChannelAdapterSpec(RemoteFileTemplate<LsEntry> remoteFileTemplate,
 			Comparator<LsEntry> comparator) {
+
 		this.target = new SftpStreamingMessageSource(remoteFileTemplate, comparator);
 	}
 
@@ -66,7 +68,6 @@ public class SftpStreamingInboundChannelAdapterSpec
 		return filter(composeFilters(new SftpRegexPatternFileListFilter(regex)));
 	}
 
-	@SuppressWarnings("unchecked")
 	private CompositeFileListFilter<LsEntry> composeFilters(FileListFilter<LsEntry> fileListFilter) {
 		CompositeFileListFilter<LsEntry> compositeFileListFilter = new CompositeFileListFilter<>();
 		compositeFileListFilter.addFilters(fileListFilter,
diff --git a/spring-integration-webflux/src/main/java/org/springframework/integration/webflux/dsl/WebFluxInboundEndpointSpec.java b/spring-integration-webflux/src/main/java/org/springframework/integration/webflux/dsl/WebFluxInboundEndpointSpec.java
index 9f017eeb01..6f66ca74c7 100644
--- a/spring-integration-webflux/src/main/java/org/springframework/integration/webflux/dsl/WebFluxInboundEndpointSpec.java
+++ b/spring-integration-webflux/src/main/java/org/springframework/integration/webflux/dsl/WebFluxInboundEndpointSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2017-2019 the original author or authors.
+ * Copyright 2017-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -32,7 +32,7 @@ import org.springframework.web.reactive.accept.RequestedContentTypeResolver;
 public class WebFluxInboundEndpointSpec
 		extends HttpInboundEndpointSupportSpec<WebFluxInboundEndpointSpec, WebFluxInboundEndpoint> {
 
-	WebFluxInboundEndpointSpec(WebFluxInboundEndpoint gateway, String... path) {
+	protected WebFluxInboundEndpointSpec(WebFluxInboundEndpoint gateway, String... path) {
 		super(gateway, path);
 	}
 
diff --git a/spring-integration-webflux/src/main/java/org/springframework/integration/webflux/dsl/WebFluxMessageHandlerSpec.java b/spring-integration-webflux/src/main/java/org/springframework/integration/webflux/dsl/WebFluxMessageHandlerSpec.java
index 38725ea378..431851d942 100644
--- a/spring-integration-webflux/src/main/java/org/springframework/integration/webflux/dsl/WebFluxMessageHandlerSpec.java
+++ b/spring-integration-webflux/src/main/java/org/springframework/integration/webflux/dsl/WebFluxMessageHandlerSpec.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2017-2019 the original author or authors.
+ * Copyright 2017-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -46,17 +46,17 @@ import org.springframework.web.reactive.function.client.WebClient;
 public class WebFluxMessageHandlerSpec
 		extends BaseHttpMessageHandlerSpec<WebFluxMessageHandlerSpec, WebFluxRequestExecutingMessageHandler> {
 
-	private final WebClient webClient;
+	protected final WebClient webClient; // NOSONAR - final
 
-	WebFluxMessageHandlerSpec(URI uri, WebClient webClient) {
+	protected WebFluxMessageHandlerSpec(URI uri, WebClient webClient) {
 		this(new ValueExpression<>(uri), webClient);
 	}
 
-	WebFluxMessageHandlerSpec(String uri, WebClient webClient) {
+	protected WebFluxMessageHandlerSpec(String uri, WebClient webClient) {
 		this(new LiteralExpression(uri), webClient);
 	}
 
-	WebFluxMessageHandlerSpec(Expression uriExpression, WebClient webClient) {
+	protected WebFluxMessageHandlerSpec(Expression uriExpression, WebClient webClient) {
 		super(new WebFluxRequestExecutingMessageHandler(uriExpression, webClient));
 		this.webClient = webClient;
 	}
diff --git a/src/reference/asciidoc/dsl.adoc b/src/reference/asciidoc/dsl.adoc
index 909c554d4c..4efa05459e 100644
--- a/src/reference/asciidoc/dsl.adoc
+++ b/src/reference/asciidoc/dsl.adoc
@@ -1202,3 +1202,63 @@ That `errorRecovererFlow` can be used as follows:
 private Function<String, String> errorRecovererFlowGateway;
 ----
 ====
+
+[[java-dsl-extensions]]
+=== DSL Extensions
+
+Starting with version 5.3, an `IntegrationFlowExtension` has been introduced to allow extension of the existing Java DSL with custom or composed EIP-operators.
+All that is needed is an extension of this class that provides methods which can be used in the `IntegrationFlow` bean definitions.
+The extension class can also be used for custom `IntegrationComponentSpec` configuration; for example, missed or default options can be implemented in the existing `IntegrationComponentSpec` extension.
+The sample below demonstrates a composite custom operator and usage of an `AggregatorSpec` extension for a default custom `outputProcessor`:
+
+====
+[source,java]
+----
+public class CustomIntegrationFlowDefinition
+        extends IntegrationFlowExtension<CustomIntegrationFlowDefinition> {
+
+    public CustomIntegrationFlowDefinition upperCaseAfterSplit() {
+        return split()
+                .transform("payload.toUpperCase()");
+    }
+
+    public CustomIntegrationFlowDefinition customAggregate(Consumer<CustomAggregatorSpec> aggregator) {
+        return register(new CustomAggregatorSpec(), aggregator);
+    }
+
+}
+
+public class CustomAggregatorSpec extends AggregatorSpec {
+
+    CustomAggregatorSpec() {
+        outputProcessor(group ->
+                group.getMessages()
+                        .stream()
+                        .map(Message::getPayload)
+                        .map(String.class::cast)
+                        .collect(Collectors.joining(", ")));
+    }
+
+}
+----
+====
+
+For a method chain flow the new DSL operator in these extensions must return the extension class.
+This way a target `IntegrationFlow` definition will work with new and existing DSL operators:
+
+====
+[source,java]
+----
+@Bean
+public IntegrationFlow customFlowDefinition() {
+    return
+            new CustomIntegrationFlowDefinition()
+                    .log()
+                    .upperCaseAfterSplit()
+                    .channel("innerChannel")
+                    .customAggregate(customAggregatorSpec ->
+                            customAggregatorSpec.expireGroupsUponCompletion(true))
+                    .logAndReply();
+}
+----
+====
diff --git a/src/reference/asciidoc/whats-new.adoc b/src/reference/asciidoc/whats-new.adoc
index b6c3a8f5cd..be8a4600f6 100644
--- a/src/reference/asciidoc/whats-new.adoc
+++ b/src/reference/asciidoc/whats-new.adoc
@@ -27,18 +27,20 @@ See its JavaDocs and <<./graph.adoc#integration-graph,Integration Graph>> for mo
 The `ReactiveMessageHandler` is now natively supported in the framework.
 See <<./reactive-streams.adoc/reactive-message-handler,ReactiveMessageHandler>> for more information.
 
+[[x5.3-java-dsl-extensions]]
+==== Java DSL Extensions
+
+A new `IntegrationFlowExtension` API has been introduced to allow extension of the existing Java DSL with custom or composed EIP-operators.
+This also can be used to introduce customizers for any out-of-the-box `IntegrationComponentSpec` extensions.
+See <<./dsl.adoc/java-dsl-extensions,DSL Extensions>> for more information.
+
+
 [[x5.3-mongodb-reactive-channel-adapters]]
 ==== MongoDB Reactive Channel Adapters
 
 `spring-integration-mongodb` module now provides channel adapter implementations for Reactive MongoDB driver support in Spring Data.
 See <<./mongodb.adoc#mongodb-reactive-channel-adapters,MongoDB Reactive Channel Adapters>> for more information.
 
-[[x5.3-AbstractCorrelatingMessageHandler]]
-==== Aggregator Changes
-
-If the `MessageGroupProcessor` returns a `Message`, the `MessageBuilder.popSequenceDetails()` is performed on the output message if the `sequenceDetails` matches with first message of group.
-See <<./aggregator.adoc#aggregator-api,Aggregator Programming Model>> for more information.
-
 [[x5.3-general]]
 === General Changes
 
@@ -48,6 +50,9 @@ See <<./gateway.adoc/gateway-calling-default-methods,Invoking `default` Methods>
 Internal components (such as `_org.springframework.integration.errorLogger`) now have a shortened name when they are represented in the integration graph.
 See <<./graph.adoc#integration-graph,Integration Graph>> for more information.
 
+In the aggregator, when the `MessageGroupProcessor` returns a `Message`, the `MessageBuilder.popSequenceDetails()` is performed on the output message if the `sequenceDetails` matches the header in the first message of the group.
+See <<./aggregator.adoc#aggregator-api,Aggregator Programming Model>> for more information.
+
 [[x5.3-amqp]]
 === AMQP Changes