INT-4458: Do not expose recursive generics API (#2432)

* INT-4458: Do not expose recursive generics API

JIRA: https://jira.spring.io/browse/INT-4458

According Kotlin generics system restrictions we can't expose API
based on the recursive generics, like we have with Java DSL for JMS

* Replace explicit recursive generics on factory method with the wildcard (`?`).
This way both Kotlin and Java are able to instantiate target object and perform
the proper chain API auto-completion
* Fix `JmsInboundChannelAdapterSpec` to deal with provided `S` type for the
`configureListenerContainer()` - the way we can configure a `JmsDefaultListenerContainerSpec`
* Add `kotlin-spring` Gradle plugin to avoid extra `open` modificator on `@Bean` methods
* Add `JmsDslKotlinTests.kt`

**Cherry-pick to 5.0.x excluding Kotlin support**

* Fix `Amqp` DSL factory for recursive generics

* Polishing for Kotlin tests

Author: artembilan

build.gradle

@@ -1,12 +1,13 @@
 buildscript {
-	ext.kotlinVersion = '1.2.40'
+	ext.kotlinVersion = '1.2.41'
 	repositories {
 		maven { url 'https://repo.spring.io/plugins-release' }
 	}
 	dependencies {
 		classpath 'io.spring.gradle:docbook-reference-plugin:0.3.1'
 		classpath 'org.asciidoctor:asciidoctor-gradle-plugin:1.5.3'
 		classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlinVersion"
+		classpath "org.jetbrains.kotlin:kotlin-allopen:$kotlinVersion"
 	}
 }
 
@@ -61,6 +62,7 @@ subprojects { subproject ->
 	apply plugin: 'jacoco'
 	apply plugin: 'checkstyle'
 	apply plugin: 'kotlin'
+	apply plugin: 'kotlin-spring'
 
 	sourceSets {
 		test {
@@ -77,6 +79,7 @@ subprojects { subproject ->
 
 	compileTestKotlin {
 		kotlinOptions {
+			freeCompilerArgs = ['-Xjsr305=strict']
 			jvmTarget = '1.8'
 		}
 	}
@@ -176,7 +179,7 @@ subprojects { subproject ->
 				exclude group: 'org.jetbrains.kotlin', module: 'kotlin-reflect'
 		}
 
-		testCompile "org.jetbrains.kotlin:kotlin-stdlib:$kotlinVersion"
+		testCompile "org.jetbrains.kotlin:kotlin-stdlib-jdk8:$kotlinVersion"
 		testRuntime "org.jetbrains.kotlin:kotlin-reflect:$kotlinVersion"
 
 	}

spring-integration-amqp/src/main/java/org/springframework/integration/amqp/dsl/Amqp.java

@@ -53,8 +53,8 @@ public static AmqpInboundGatewaySMLCSpec inboundGateway(ConnectionFactory connec
 	 * @param queueNames the queueNames.
 	 * @return the AmqpInboundGatewaySpec.
 	 */
-	public static AmqpInboundGatewaySMLCSpec inboundGateway(ConnectionFactory connectionFactory, AmqpTemplate amqpTemplate,
-			String... queueNames) {
+	public static AmqpInboundGatewaySMLCSpec inboundGateway(ConnectionFactory connectionFactory,
+			AmqpTemplate amqpTemplate, String... queueNames) {
 
 		SimpleMessageListenerContainer listenerContainer = new SimpleMessageListenerContainer(connectionFactory);
 		listenerContainer.setQueueNames(queueNames);
@@ -81,8 +81,8 @@ public static AmqpInboundGatewaySMLCSpec inboundGateway(ConnectionFactory connec
 	 * @param queues the queues.
 	 * @return the AmqpInboundGatewaySpec.
 	 */
-	public static AmqpInboundGatewaySMLCSpec inboundGateway(ConnectionFactory connectionFactory, AmqpTemplate amqpTemplate,
-			Queue... queues) {
+	public static AmqpInboundGatewaySMLCSpec inboundGateway(ConnectionFactory connectionFactory,
+			AmqpTemplate amqpTemplate, Queue... queues) {
 
 		SimpleMessageListenerContainer listenerContainer = new SimpleMessageListenerContainer(connectionFactory);
 		listenerContainer.setQueues(queues);
@@ -266,51 +266,41 @@ public static AmqpAsyncOutboundGatewaySpec asyncOutboundGateway(AsyncRabbitTempl
 	/**
 	 * Create an initial AmqpPollableMessageChannelSpec.
 	 * @param connectionFactory the connectionFactory.
-	 * @param <S> the spec type.
 	 * @return the AmqpPollableMessageChannelSpec.
 	 */
-	public static <S extends AmqpPollableMessageChannelSpec<S>> AmqpPollableMessageChannelSpec<S> pollableChannel(
-			ConnectionFactory connectionFactory) {
-
+	public static AmqpPollableMessageChannelSpec<?> pollableChannel(ConnectionFactory connectionFactory) {
 		return pollableChannel(null, connectionFactory);
 	}
 
 	/**
 	 * Create an initial AmqpPollableMessageChannelSpec.
 	 * @param id the id.
 	 * @param connectionFactory the connectionFactory.
-	 * @param <S> the spec type.
 	 * @return the AmqpPollableMessageChannelSpec.
 	 */
-	public static <S extends AmqpPollableMessageChannelSpec<S>> AmqpPollableMessageChannelSpec<S> pollableChannel(
-			String id, ConnectionFactory connectionFactory) {
-
-		return new AmqpPollableMessageChannelSpec<S>(connectionFactory).id(id);
+	public static AmqpPollableMessageChannelSpec<?> pollableChannel(String id, ConnectionFactory connectionFactory) {
+		return new AmqpPollableMessageChannelSpec<>(connectionFactory)
+				.id(id);
 	}
 
 	/**
 	 * Create an initial AmqpMessageChannelSpec.
 	 * @param connectionFactory the connectionFactory.
-	 * @param <S> the spec type.
 	 * @return the AmqpMessageChannelSpec.
 	 */
-	public static <S extends AmqpMessageChannelSpec<S>> AmqpMessageChannelSpec<S> channel(
-			ConnectionFactory connectionFactory) {
-
+	public static AmqpMessageChannelSpec<?> channel(ConnectionFactory connectionFactory) {
 		return channel(null, connectionFactory);
 	}
 
 	/**
 	 * Create an initial AmqpMessageChannelSpec.
 	 * @param id the id.
 	 * @param connectionFactory the connectionFactory.
-	 * @param <S> the spec type.
 	 * @return the AmqpMessageChannelSpec.
 	 */
-	public static <S extends AmqpMessageChannelSpec<S>> AmqpMessageChannelSpec<S> channel(String id,
-			ConnectionFactory connectionFactory) {
-
-		return new AmqpMessageChannelSpec<S>(connectionFactory).id(id);
+	public static AmqpMessageChannelSpec<?> channel(String id, ConnectionFactory connectionFactory) {
+		return new AmqpMessageChannelSpec<>(connectionFactory)
+				.id(id);
 	}
 
 	/**

spring-integration-core/src/test/kotlin/org/springframework/integration/dsl/routers/RouterDslTests.kt

@@ -68,10 +68,10 @@ class RouterDslTests {
 
     @Configuration
     @EnableIntegration
-    open class Config {
+    class Config {
 
         @Bean
-        open fun routerTwoSubFlows() =
+        fun routerTwoSubFlows() =
                 IntegrationFlow { f ->
                     f.split()
                             .route<Int, Boolean>({ p -> p % 2 == 0 },

spring-integration-jms/src/main/java/org/springframework/integration/jms/dsl/Jms.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2014-2017 the original author or authors.
+ * Copyright 2014-2018 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.
@@ -36,47 +36,40 @@ public final class Jms {
 	/**
 	 * The factory to produce a {@link JmsPollableMessageChannelSpec}.
 	 * @param connectionFactory the JMS ConnectionFactory to build on
-	 * @param <S>               the {@link JmsPollableMessageChannelSpec} inheritor type
 	 * @return the {@link JmsPollableMessageChannelSpec} instance
 	 */
-	public static <S extends JmsPollableMessageChannelSpec<S>> JmsPollableMessageChannelSpec<S> pollableChannel(
-			ConnectionFactory connectionFactory) {
+	public static JmsPollableMessageChannelSpec<?> pollableChannel(ConnectionFactory connectionFactory) {
 		return pollableChannel(null, connectionFactory);
 	}
 
 	/**
 	 * The factory to produce a {@link JmsPollableMessageChannelSpec}.
 	 * @param id                the bean name for the target {@code PollableChannel} component
 	 * @param connectionFactory the JMS ConnectionFactory to build on
-	 * @param <S>               the {@link JmsPollableMessageChannelSpec} inheritor type
 	 * @return the {@link JmsPollableMessageChannelSpec} instance
 	 */
-	public static <S extends JmsPollableMessageChannelSpec<S>> JmsPollableMessageChannelSpec<S> pollableChannel(
-			String id, ConnectionFactory connectionFactory) {
-		return new JmsPollableMessageChannelSpec<S>(connectionFactory).id(id);
+	public static JmsPollableMessageChannelSpec<?> pollableChannel(String id, ConnectionFactory connectionFactory) {
+		return new JmsPollableMessageChannelSpec<>(connectionFactory).id(id);
 	}
 
 	/**
 	 * The factory to produce a {@link JmsMessageChannelSpec}.
 	 * @param connectionFactory the JMS ConnectionFactory to build on
-	 * @param <S>               the {@link JmsMessageChannelSpec} inheritor type
 	 * @return the {@link JmsMessageChannelSpec} instance
 	 */
-	public static <S extends JmsMessageChannelSpec<S>> JmsMessageChannelSpec<S> channel(
-			ConnectionFactory connectionFactory) {
+	public static JmsMessageChannelSpec<?> channel(ConnectionFactory connectionFactory) {
 		return channel(null, connectionFactory);
 	}
 
 	/**
 	 * The factory to produce a {@link JmsMessageChannelSpec}.
 	 * @param id                the bean name for the target {@code MessageChannel} component
 	 * @param connectionFactory the JMS ConnectionFactory to build on
-	 * @param <S>               the {@link JmsMessageChannelSpec} inheritor type
 	 * @return the {@link JmsMessageChannelSpec} instance
 	 */
-	public static <S extends JmsMessageChannelSpec<S>> JmsMessageChannelSpec<S> channel(String id,
-			ConnectionFactory connectionFactory) {
-		return new JmsMessageChannelSpec<S>(connectionFactory).id(id);
+	public static JmsMessageChannelSpec<?> channel(String id, ConnectionFactory connectionFactory) {
+		return new JmsMessageChannelSpec<>(connectionFactory)
+				.id(id);
 	}
 
 	/**
@@ -96,18 +89,17 @@ public static JmsPublishSubscribeMessageChannelSpec publishSubscribeChannel(Conn
 	 */
 	public static JmsPublishSubscribeMessageChannelSpec publishSubscribeChannel(String id,
 			ConnectionFactory connectionFactory) {
+
 		return new JmsPublishSubscribeMessageChannelSpec(connectionFactory).id(id);
 	}
 
 	/**
 	 * The factory to produce a {@link JmsOutboundChannelAdapterSpec}.
 	 * @param jmsTemplate the JmsTemplate to build on
-	 * @param <S>         the {@link JmsOutboundChannelAdapterSpec} inheritor type
 	 * @return the {@link JmsOutboundChannelAdapterSpec} instance
 	 */
-	public static <S extends JmsOutboundChannelAdapterSpec<S>> JmsOutboundChannelAdapterSpec<S> outboundAdapter(
-			JmsTemplate jmsTemplate) {
-		return new JmsOutboundChannelAdapterSpec<S>(jmsTemplate);
+	public static JmsOutboundChannelAdapterSpec<?> outboundAdapter(JmsTemplate jmsTemplate) {
+		return new JmsOutboundChannelAdapterSpec<>(jmsTemplate);
 	}
 
 	/**
@@ -117,18 +109,17 @@ public static <S extends JmsOutboundChannelAdapterSpec<S>> JmsOutboundChannelAda
 	 */
 	public static JmsOutboundChannelAdapterSpec.JmsOutboundChannelSpecTemplateAware outboundAdapter(
 			ConnectionFactory connectionFactory) {
+
 		return new JmsOutboundChannelAdapterSpec.JmsOutboundChannelSpecTemplateAware(connectionFactory);
 	}
 
 	/**
 	 * The factory to produce a {@link JmsInboundChannelAdapterSpec}.
 	 * @param jmsTemplate the JmsTemplate to build on
-	 * @param <S>         the {@link JmsInboundChannelAdapterSpec} inheritor type
 	 * @return the {@link JmsInboundChannelAdapterSpec} instance
 	 */
-	public static <S extends JmsInboundChannelAdapterSpec<S>> JmsInboundChannelAdapterSpec<S> inboundAdapter(
-			JmsTemplate jmsTemplate) {
-		return new JmsInboundChannelAdapterSpec<S>(jmsTemplate);
+	public static JmsInboundChannelAdapterSpec<?> inboundAdapter(JmsTemplate jmsTemplate) {
+		return new JmsInboundChannelAdapterSpec<>(jmsTemplate);
 	}
 
 	/**
@@ -138,6 +129,7 @@ public static <S extends JmsInboundChannelAdapterSpec<S>> JmsInboundChannelAdapt
 	 */
 	public static JmsInboundChannelAdapterSpec.JmsInboundChannelSpecTemplateAware inboundAdapter(
 			ConnectionFactory connectionFactory) {
+
 		return new JmsInboundChannelAdapterSpec.JmsInboundChannelSpecTemplateAware(connectionFactory);
 	}
 
@@ -153,12 +145,10 @@ public static JmsOutboundGatewaySpec outboundGateway(ConnectionFactory connectio
 	/**
 	 * The factory to produce a {@link JmsOutboundGatewaySpec}.
 	 * @param listenerContainer the JMS {@link AbstractMessageListenerContainer} to build on
-	 * @param <S> the {@link JmsInboundGatewaySpec} inheritor type
 	 * @return the {@link JmsOutboundGatewaySpec} instance
 	 */
-	public static <S extends JmsInboundGatewaySpec<S>> JmsInboundGatewaySpec<S> inboundGateway(
-			AbstractMessageListenerContainer listenerContainer) {
-		return new JmsInboundGatewaySpec<S>(listenerContainer);
+	public static JmsInboundGatewaySpec<?> inboundGateway(AbstractMessageListenerContainer listenerContainer) {
+		return new JmsInboundGatewaySpec<>(listenerContainer);
 	}
 
 	/**
@@ -168,26 +158,35 @@ public static <S extends JmsInboundGatewaySpec<S>> JmsInboundGatewaySpec<S> inbo
 	 */
 	public static JmsInboundGatewaySpec.JmsInboundGatewayListenerContainerSpec<JmsDefaultListenerContainerSpec, DefaultMessageListenerContainer>
 	inboundGateway(ConnectionFactory connectionFactory) {
-		return inboundGateway(connectionFactory, DefaultMessageListenerContainer.class);
+
+		try {
+			return new JmsInboundGatewaySpec.JmsInboundGatewayListenerContainerSpec<>(
+					new JmsDefaultListenerContainerSpec()
+							.connectionFactory(connectionFactory));
+		}
+		catch (Exception e) {
+			throw new IllegalStateException(e);
+		}
 	}
 
 	/**
 	 * The factory to produce a {@link JmsOutboundGatewaySpec}.
 	 * @param connectionFactory the JMS ConnectionFactory to build on
 	 * @param containerClass    the {@link AbstractMessageListenerContainer} implementation class
 	 *                          to instantiate listener container
-	 * @param <S>               the {@link JmsListenerContainerSpec} inheritor type
 	 * @param <C>               the {@link AbstractMessageListenerContainer} inheritor type
 	 * @return the {@link JmsOutboundGatewaySpec} instance
 	 */
-	public static <S extends JmsListenerContainerSpec<S, C>, C extends AbstractMessageListenerContainer>
-	JmsInboundGatewaySpec.JmsInboundGatewayListenerContainerSpec<S, C> inboundGateway(ConnectionFactory connectionFactory,
-			Class<C> containerClass) {
+	@SuppressWarnings({ "rawtypes", "unchecked" })
+	public static <C extends AbstractMessageListenerContainer>
+	JmsInboundGatewaySpec.JmsInboundGatewayListenerContainerSpec<?, C> inboundGateway(
+			ConnectionFactory connectionFactory, Class<C> containerClass) {
+
 		try {
-			JmsListenerContainerSpec<S, C> spec =
-					new JmsListenerContainerSpec<S, C>(containerClass)
+			JmsListenerContainerSpec<?, C> spec =
+					new JmsListenerContainerSpec<>(containerClass)
 							.connectionFactory(connectionFactory);
-			return new JmsInboundGatewaySpec.JmsInboundGatewayListenerContainerSpec<S, C>(spec);
+			return new JmsInboundGatewaySpec.JmsInboundGatewayListenerContainerSpec(spec);
 		}
 		catch (Exception e) {
 			throw new IllegalStateException(e);
@@ -197,13 +196,10 @@ JmsInboundGatewaySpec.JmsInboundGatewayListenerContainerSpec<S, C> inboundGatewa
 	/**
 	 * The factory to produce a {@link JmsMessageDrivenChannelAdapterSpec}.
 	 * @param listenerContainer the {@link AbstractMessageListenerContainer} to build on
-	 * @param <S>               the {@link JmsMessageDrivenChannelAdapterSpec} inheritor type
 	 * @return the {@link JmsMessageDrivenChannelAdapterSpec} instance
 	 */
-	public static <S extends JmsMessageDrivenChannelAdapterSpec<S>>
-	JmsMessageDrivenChannelAdapterSpec<S> messageDrivenChannelAdapter(
-			AbstractMessageListenerContainer listenerContainer) {
-		return new JmsMessageDrivenChannelAdapterSpec<S>(listenerContainer);
+	public static JmsMessageDrivenChannelAdapterSpec<?> messageDrivenChannelAdapter(AbstractMessageListenerContainer listenerContainer) {
+		return new JmsMessageDrivenChannelAdapterSpec<>(listenerContainer);
 	}
 
 	/**
@@ -215,7 +211,8 @@ JmsMessageDrivenChannelAdapterSpec<S> messageDrivenChannelAdapter(
 	messageDrivenChannelAdapter(ConnectionFactory connectionFactory) {
 		try {
 			return new JmsMessageDrivenChannelAdapterSpec.JmsMessageDrivenChannelAdapterListenerContainerSpec<>(
-					new JmsDefaultListenerContainerSpec().connectionFactory(connectionFactory));
+					new JmsDefaultListenerContainerSpec()
+							.connectionFactory(connectionFactory));
 		}
 		catch (Exception e) {
 			throw new IllegalStateException(e);
@@ -227,18 +224,18 @@ JmsMessageDrivenChannelAdapterSpec<S> messageDrivenChannelAdapter(
 	 * @param connectionFactory the JMS ConnectionFactory to build on
 	 * @param containerClass    the {@link AbstractMessageListenerContainer} implementation class
 	 *                          to instantiate listener container
-	 * @param <S>               the {@link JmsListenerContainerSpec} inheritor type
 	 * @param <C>               the {@link AbstractMessageListenerContainer} inheritor type
 	 * @return the {@link JmsMessageDrivenChannelAdapterSpec} instance
 	 */
-	public static <S extends JmsListenerContainerSpec<S, C>, C extends AbstractMessageListenerContainer>
-	JmsMessageDrivenChannelAdapterSpec.JmsMessageDrivenChannelAdapterListenerContainerSpec<S, C>
+	@SuppressWarnings({ "rawtypes", "unchecked" })
+	public static <C extends AbstractMessageListenerContainer>
+	JmsMessageDrivenChannelAdapterSpec.JmsMessageDrivenChannelAdapterListenerContainerSpec<?, C>
 	messageDrivenChannelAdapter(ConnectionFactory connectionFactory, Class<C> containerClass) {
 		try {
-			S spec =
-					new JmsListenerContainerSpec<S, C>(containerClass)
+			JmsListenerContainerSpec<?, C> spec =
+					new JmsListenerContainerSpec<>(containerClass)
 							.connectionFactory(connectionFactory);
-			return new JmsMessageDrivenChannelAdapterSpec.JmsMessageDrivenChannelAdapterListenerContainerSpec<>(spec);
+			return new JmsMessageDrivenChannelAdapterSpec.JmsMessageDrivenChannelAdapterListenerContainerSpec(spec);
 		}
 		catch (Exception e) {
 			throw new IllegalStateException(e);

spring-integration-jms/src/main/java/org/springframework/integration/jms/dsl/JmsInboundGatewaySpec.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2017 the original author or authors.
+ * Copyright 2016-2018 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.
@@ -35,6 +35,7 @@
  * @param <S> the target {@link JmsInboundGatewaySpec} implementation type.
  *
  * @author Artem Bilan
+ *
  * @since 5.0
  */
 public class JmsInboundGatewaySpec<S extends JmsInboundGatewaySpec<S>>
@@ -184,9 +185,9 @@ public S extractReplyPayload(boolean extractReplyPayload) {
 	public static class JmsInboundGatewayListenerContainerSpec<S extends JmsListenerContainerSpec<S, C>, C extends AbstractMessageListenerContainer>
 			extends JmsInboundGatewaySpec<JmsInboundGatewayListenerContainerSpec<S, C>> {
 
-		private final JmsListenerContainerSpec<S, C> spec;
+		private final S spec;
 
-		JmsInboundGatewayListenerContainerSpec(JmsListenerContainerSpec<S, C> spec) {
+		JmsInboundGatewayListenerContainerSpec(S spec) {
 			super(spec.get());
 			this.spec = spec;
 			this.spec.get().setAutoStartup(false);
@@ -213,7 +214,7 @@ public JmsInboundGatewayListenerContainerSpec<S, C> destination(String destinati
 		}
 
 		public JmsInboundGatewayListenerContainerSpec<S, C> configureListenerContainer(
-				Consumer<JmsListenerContainerSpec<S, C>> configurer) {
+				Consumer<S> configurer) {
 			Assert.notNull(configurer, "'configurer' must not be null");
 			configurer.accept(this.spec);
 			return _this();