GH-9558: Expose BarrierSpec.discardChannel & triggerTimeout

Fixes: #9558
Issue link: https://github.com/spring-projects/spring-integration/issues/9558

**Auto-cherry-pick to `6.3.x` & `6.2.x`**

spring-integration-core/src/main/java/org/springframework/integration/aggregator/BarrierMessageHandler.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2015-2020 the original author or authors.
+ * Copyright 2015-2024 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.
@@ -27,6 +27,7 @@ import org.springframework.integration.handler.AbstractReplyProducingMessageHand
 import org.springframework.integration.handler.DiscardingMessageHandler;
 import org.springframework.integration.handler.MessageTriggerAction;
 import org.springframework.integration.store.SimpleMessageGroup;
+import org.springframework.lang.Nullable;
 import org.springframework.messaging.Message;
 import org.springframework.messaging.MessageChannel;
 import org.springframework.messaging.MessageHandlingException;
@@ -170,7 +171,8 @@ public class BarrierMessageHandler extends AbstractReplyProducingMessageHandler
 	}
 
 	/**
-	 * Set the name of the channel to which late arriving trigger messages are sent.
+	 * Set the name of the channel to which late arriving trigger messages are sent,
+	 * or request message does not arrive in time.
 	 * @param discardChannelName the discard channel.
 	 * @since 5.0
 	 */
@@ -179,7 +181,8 @@ public class BarrierMessageHandler extends AbstractReplyProducingMessageHandler
 	}
 
 	/**
-	 * Set the channel to which late arriving trigger messages are sent.
+	 * Set the channel to which late arriving trigger messages are sent,
+	 * or request message does not arrive in time.
 	 * @param discardChannel the discard channel.
 	 * @since 5.0
 	 */
@@ -188,8 +191,11 @@ public class BarrierMessageHandler extends AbstractReplyProducingMessageHandler
 	}
 
 	/**
+	 * Return the discard message channel for trigger action message.
+	 * @return a discard message channel.
 	 * @since 5.0
 	 */
+	@Nullable
 	@Override
 	public MessageChannel getDiscardChannel() {
 		String channelName = this.discardChannelName;

spring-integration-core/src/main/java/org/springframework/integration/dsl/BarrierSpec.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2023 the original author or authors.
+ * Copyright 2016-2024 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.
@@ -25,6 +25,8 @@ import org.springframework.integration.aggregator.DefaultAggregatingMessageGroup
 import org.springframework.integration.aggregator.HeaderAttributeCorrelationStrategy;
 import org.springframework.integration.aggregator.MessageGroupProcessor;
 import org.springframework.integration.config.ConsumerEndpointFactoryBean;
+import org.springframework.lang.Nullable;
+import org.springframework.messaging.MessageChannel;
 import org.springframework.util.Assert;
 
 /**
@@ -43,6 +45,15 @@ public class BarrierSpec extends ConsumerEndpointSpec<BarrierSpec, BarrierMessag
 	private CorrelationStrategy correlationStrategy =
 			new HeaderAttributeCorrelationStrategy(IntegrationMessageHeaderAccessor.CORRELATION_ID);
 
+	@Nullable
+	private MessageChannel discardChannel;
+
+	@Nullable
+	private String discardChannelName;
+
+	@Nullable
+	private Long triggerTimeout;
+
 	protected BarrierSpec(long timeout) {
 		super(null);
 		this.timeout = timeout;
@@ -60,9 +71,57 @@ public class BarrierSpec extends ConsumerEndpointSpec<BarrierSpec, BarrierMessag
 		return this;
 	}
 
+	/**
+	 * Set the channel to which late arriving trigger messages are sent,
+	 * or request message does not arrive in time.
+	 * @param discardChannel the message channel for discarded triggers.
+	 * @return the spec
+	 * @since 6.2.10
+	 */
+	public BarrierSpec discardChannel(@Nullable MessageChannel discardChannel) {
+		this.discardChannel = discardChannel;
+		return this;
+	}
+
+	/**
+	 * Set the channel bean name to which late arriving trigger messages are sent,
+	 * or request message does not arrive in time.
+	 * @param discardChannelName the message channel for discarded triggers.
+	 * @return the spec
+	 * @since 6.2.10
+	 */
+	public BarrierSpec discardChannel(@Nullable String discardChannelName) {
+		this.discardChannelName = discardChannelName;
+		return this;
+	}
+
+	/**
+	 * Set the timeout in milliseconds when waiting for a request message.
+	 * @param triggerTimeout the timeout in milliseconds when waiting for a request message.
+	 * @return the spec
+	 * @since 6.2.10
+	 */
+	public BarrierSpec triggerTimeout(long triggerTimeout) {
+		this.triggerTimeout = triggerTimeout;
+		return this;
+	}
+
 	@Override
 	public Tuple2<ConsumerEndpointFactoryBean, BarrierMessageHandler> doGet() {
-		this.handler = new BarrierMessageHandler(this.timeout, this.outputProcessor, this.correlationStrategy);
+		if (this.triggerTimeout == null) {
+			this.handler = new BarrierMessageHandler(this.timeout, this.outputProcessor, this.correlationStrategy);
+		}
+		else {
+			this.handler =
+					new BarrierMessageHandler(this.timeout, this.triggerTimeout, this.outputProcessor,
+							this.correlationStrategy);
+		}
+		if (this.discardChannel != null) {
+			this.handler.setDiscardChannel(this.discardChannel);
+		}
+		else if (this.discardChannelName != null) {
+			this.handler.setDiscardChannelName(this.discardChannelName);
+		}
 		return super.doGet();
 	}
 

spring-integration-core/src/test/java/org/springframework/integration/dsl/correlation/CorrelationHandlerTests.java

@@ -300,6 +300,7 @@ public class CorrelationHandlerTests {
 			return f -> f
 					.barrier(10000, b -> b
 							.correlationStrategy(new HeaderAttributeCorrelationStrategy(BARRIER))
+							.discardChannel("nullChannel")
 							.outputProcessor(g ->
 									g.getMessages()
 											.stream()