Merge spring-integration-kotlin-dsl project

* Migrate all the Kotlin tests to use new Kotlin DSL
* Upgrade to the latest Kotlin
* Generate KDocs

spring-integration-core/src/main/kotlin/org/springframework/integration/dsl/IntegrationFlowDsl.kt

@@ -0,0 +1,159 @@
+/*
+ * 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 org.reactivestreams.Publisher
+import org.springframework.integration.core.MessageSource
+import org.springframework.integration.endpoint.MessageProducerSupport
+import org.springframework.integration.gateway.MessagingGatewaySupport
+import org.springframework.messaging.Message
+import org.springframework.messaging.MessageChannel
+import java.util.function.Consumer
+
+private fun buildIntegrationFlow(flowBuilder: IntegrationFlowBuilder,
+								 flow: (KotlinIntegrationFlowDefinition) -> Unit): IntegrationFlow {
+
+	flow(KotlinIntegrationFlowDefinition(flowBuilder))
+	return flowBuilder.get()
+}
+
+/**
+ * Functional [IntegrationFlow] definition in Kotlin DSL for [IntegrationFlow] lambdas.
+ *
+ * @author Artem Bilan
+ */
+fun integrationFlow(flow: KotlinIntegrationFlowDefinition.() -> Unit) =
+		IntegrationFlow {
+			flow(KotlinIntegrationFlowDefinition(it))
+		}
+
+/**
+ * Functional [IntegrationFlow] definition in Kotlin DSL for [IntegrationFlows.from] -
+ * `IntegrationFlows.from(Class<?>, Consumer<GatewayProxySpec>)` factory method.
+ *
+ * @author Artem Bilan
+ */
+inline fun <reified T> integrationFlow(
+		crossinline gateway: GatewayProxySpec.() -> Unit = {},
+		flow: KotlinIntegrationFlowDefinition.() -> Unit): IntegrationFlow {
+
+	val flowBuilder = IntegrationFlows.from(T::class.java) { gateway(it) }
+	flow(KotlinIntegrationFlowDefinition(flowBuilder))
+	return flowBuilder.get()
+}
+
+/**
+ * Functional [IntegrationFlow] definition in Kotlin DSL for [IntegrationFlows.from] -
+ * `IntegrationFlows.from(String, Boolean)` factory method.
+ *
+ * @author Artem Bilan
+ */
+fun integrationFlow(channelName: String, fixedSubscriber: Boolean = false,
+					flow: KotlinIntegrationFlowDefinition.() -> Unit) =
+		buildIntegrationFlow(IntegrationFlows.from(channelName, fixedSubscriber), flow)
+
+/**
+ * Functional [IntegrationFlow] definition in Kotlin DSL for [IntegrationFlows.from] -
+ * `IntegrationFlows.from(MessageChannel)` factory method.
+ *
+ * @author Artem Bilan
+ */
+fun integrationFlow(channel: MessageChannel, flow: KotlinIntegrationFlowDefinition.() -> Unit) =
+		buildIntegrationFlow(IntegrationFlows.from(channel), flow)
+
+/**
+ * Functional [IntegrationFlow] definition in Kotlin DSL for [IntegrationFlows.from]  -
+ * `IntegrationFlows.from(MessageSource<*>, Consumer<SourcePollingChannelAdapterSpec>)` factory method.
+ *
+ * @author Artem Bilan
+ */
+fun integrationFlow(messageSource: MessageSource<*>,
+					options: SourcePollingChannelAdapterSpec.() -> Unit = {},
+					flow: KotlinIntegrationFlowDefinition.() -> Unit) =
+		buildIntegrationFlow(IntegrationFlows.from(messageSource, Consumer { options(it) }), flow)
+
+/**
+ * Functional [IntegrationFlow] definition in Kotlin DSL for [IntegrationFlows.from]  -
+ * `IntegrationFlows.from(MessageSourceSpec<*>, Consumer<SourcePollingChannelAdapterSpec>)` factory method.
+ *
+ * @author Artem Bilan
+ */
+fun integrationFlow(messageSource: MessageSourceSpec<*, out MessageSource<*>>,
+					options: SourcePollingChannelAdapterSpec.() -> Unit = {},
+					flow: KotlinIntegrationFlowDefinition.() -> Unit) =
+		buildIntegrationFlow(IntegrationFlows.from(messageSource, options), flow)
+
+/**
+ * Functional [IntegrationFlow] definition in Kotlin DSL for [IntegrationFlows.from] -
+ * `IntegrationFlows.from(Supplier<*>, Consumer<SourcePollingChannelAdapterSpec>)` factory method.
+ *
+ * @author Artem Bilan
+ */
+fun integrationFlow(source: () -> Any,
+					options: SourcePollingChannelAdapterSpec.() -> Unit = {},
+					flow: KotlinIntegrationFlowDefinition.() -> Unit) =
+		buildIntegrationFlow(IntegrationFlows.from(source, options), flow)
+
+/**
+ * Functional [IntegrationFlow] definition in Kotlin DSL for [IntegrationFlows.from] -
+ * `IntegrationFlows.from(Publisher<out Message<*>>)` factory method.
+ *
+ * @author Artem Bilan
+ */
+fun integrationFlow(publisher: Publisher<out Message<*>>,
+					flow: KotlinIntegrationFlowDefinition.() -> Unit) =
+		buildIntegrationFlow(IntegrationFlows.from(publisher), flow)
+
+/**
+ * Functional [IntegrationFlow] definition in Kotlin DSL for [IntegrationFlows.from] -
+ * `IntegrationFlows.from(MessagingGatewaySupport)` factory method.
+ *
+ * @author Artem Bilan
+ */
+fun integrationFlow(gateway: MessagingGatewaySupport,
+					flow: KotlinIntegrationFlowDefinition.() -> Unit) =
+		buildIntegrationFlow(IntegrationFlows.from(gateway), flow)
+
+/**
+ * Functional [IntegrationFlow] definition in Kotlin DSL for [IntegrationFlows.from] -
+ * `IntegrationFlows.from(MessagingGatewaySpec<*, *>)` factory method.
+ *
+ * @author Artem Bilan
+ */
+fun integrationFlow(gatewaySpec: MessagingGatewaySpec<*, *>,
+					flow: KotlinIntegrationFlowDefinition.() -> Unit) =
+		buildIntegrationFlow(IntegrationFlows.from(gatewaySpec), flow)
+
+/**
+ * Functional [IntegrationFlow] definition in Kotlin DSL for [IntegrationFlows.from] -
+ * `IntegrationFlows.from(MessageProducerSupport)` factory method.
+ *
+ * @author Artem Bilan
+ */
+fun integrationFlow(producer: MessageProducerSupport,
+					flow: KotlinIntegrationFlowDefinition.() -> Unit) =
+		buildIntegrationFlow(IntegrationFlows.from(producer), flow)
+
+/**
+ * Functional [IntegrationFlow] definition in Kotlin DSL for [IntegrationFlows.from] -
+ * `IntegrationFlows.from(MessageProducerSpec<*, *>)` factory method.
+ *
+ * @author Artem Bilan
+ */
+fun integrationFlow(producerSpec: MessageProducerSpec<*, *>,
+					flow: KotlinIntegrationFlowDefinition.() -> Unit) =
+		buildIntegrationFlow(IntegrationFlows.from(producerSpec), flow)