Rework KotlinIntFlowDefinition for delegation

According Kotlin best practice it is better to not
extend from Java classes, but instead provide a
clean Kotlin API and delegate to Java one internally

* Implement all the `IntegrationFlowDefinition` methods
in the `KotlinIntegrationFlowDefinition` Kotlin way and
delegate to the provided `IntegrationFlowDefinition` instance
* Remove `@UseExperimental` and `@BuilderInference` since
we now have all the API in Kotlin
* Rework `KotlinDslTests` for support now Kotlin code style
* Remove `-Xuse-experimental` from Gradle config since we
don't use experimental API any more

spring-integration-kotlin-dsl/build.gradle

@@ -66,7 +66,7 @@ dependencyManagement {
 compileKotlin {
     kotlinOptions {
         jvmTarget = '1.8'
-        freeCompilerArgs = ['-Xjsr305=strict', '-Xuse-experimental=kotlin.Experimental']
+        freeCompilerArgs = ['-Xjsr305=strict']
         allWarningsAsErrors = true
     }
 }

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

@@ -14,8 +14,6 @@
  * limitations under the License.
  */
 
-@file:UseExperimental(kotlin.experimental.ExperimentalTypeInference::class)
-
 package org.springframework.integration.dsl
 
 import org.reactivestreams.Publisher
@@ -38,7 +36,7 @@ private fun buildIntegrationFlow(flowBuilder: IntegrationFlowBuilder,
  *
  * @author Artem Bilan
  */
-fun integrationFlow(@BuilderInference flow: KotlinIntegrationFlowDefinition.() -> Unit) =
+fun integrationFlow(flow: KotlinIntegrationFlowDefinition.() -> Unit) =
 		IntegrationFlow {
 			flow(KotlinIntegrationFlowDefinition(it))
 		}
@@ -51,7 +49,7 @@ fun integrationFlow(@BuilderInference flow: KotlinIntegrationFlowDefinition.() -
  */
 inline fun <reified T> integrationFlow(
 		crossinline gateway: (GatewayProxySpec) -> Unit = {},
-		@BuilderInference flow: KotlinIntegrationFlowDefinition.() -> Unit): IntegrationFlow {
+		flow: KotlinIntegrationFlowDefinition.() -> Unit): IntegrationFlow {
 
 	val flowBuilder = IntegrationFlows.from(T::class.java) { gateway(it) }
 	flow(KotlinIntegrationFlowDefinition(flowBuilder))
@@ -65,7 +63,7 @@ inline fun <reified T> integrationFlow(
  * @author Artem Bilan
  */
 fun integrationFlow(channelName: String, fixedSubscriber: Boolean = false,
-					@BuilderInference flow: KotlinIntegrationFlowDefinition.() -> Unit) =
+					flow: KotlinIntegrationFlowDefinition.() -> Unit) =
 		buildIntegrationFlow(IntegrationFlows.from(channelName, fixedSubscriber), flow)
 
 /**
@@ -74,7 +72,7 @@ fun integrationFlow(channelName: String, fixedSubscriber: Boolean = false,
  *
  * @author Artem Bilan
  */
-fun integrationFlow(channel: MessageChannel, @BuilderInference flow: KotlinIntegrationFlowDefinition.() -> Unit) =
+fun integrationFlow(channel: MessageChannel, flow: KotlinIntegrationFlowDefinition.() -> Unit) =
 		buildIntegrationFlow(IntegrationFlows.from(channel), flow)
 
 /**
@@ -85,7 +83,7 @@ fun integrationFlow(channel: MessageChannel, @BuilderInference flow: KotlinInteg
  */
 fun integrationFlow(messageSource: MessageSource<*>,
 					options: (SourcePollingChannelAdapterSpec) -> Unit = {},
-					@BuilderInference flow: KotlinIntegrationFlowDefinition.() -> Unit) =
+					flow: KotlinIntegrationFlowDefinition.() -> Unit) =
 		buildIntegrationFlow(IntegrationFlows.from(messageSource, Consumer { options(it) }), flow)
 
 /**
@@ -96,7 +94,7 @@ fun integrationFlow(messageSource: MessageSource<*>,
  */
 fun integrationFlow(messageSource: MessageSourceSpec<*, out MessageSource<*>>,
 					options: (SourcePollingChannelAdapterSpec) -> Unit = {},
-					@BuilderInference flow: KotlinIntegrationFlowDefinition.() -> Unit) =
+					flow: KotlinIntegrationFlowDefinition.() -> Unit) =
 		buildIntegrationFlow(IntegrationFlows.from(messageSource, options), flow)
 
 /**
@@ -107,7 +105,7 @@ fun integrationFlow(messageSource: MessageSourceSpec<*, out MessageSource<*>>,
  */
 fun integrationFlow(source: () -> Any,
 					options: (SourcePollingChannelAdapterSpec) -> Unit = {},
-					@BuilderInference flow: KotlinIntegrationFlowDefinition.() -> Unit) =
+					flow: KotlinIntegrationFlowDefinition.() -> Unit) =
 		buildIntegrationFlow(IntegrationFlows.from(source, options), flow)
 
 /**
@@ -117,7 +115,7 @@ fun integrationFlow(source: () -> Any,
  * @author Artem Bilan
  */
 fun integrationFlow(publisher: Publisher<out Message<*>>,
-					@BuilderInference flow: KotlinIntegrationFlowDefinition.() -> Unit) =
+					flow: KotlinIntegrationFlowDefinition.() -> Unit) =
 		buildIntegrationFlow(IntegrationFlows.from(publisher), flow)
 
 /**
@@ -127,7 +125,7 @@ fun integrationFlow(publisher: Publisher<out Message<*>>,
  * @author Artem Bilan
  */
 fun integrationFlow(gateway: MessagingGatewaySupport,
-					@BuilderInference flow: KotlinIntegrationFlowDefinition.() -> Unit) =
+					flow: KotlinIntegrationFlowDefinition.() -> Unit) =
 		buildIntegrationFlow(IntegrationFlows.from(gateway), flow)
 
 /**
@@ -137,7 +135,7 @@ fun integrationFlow(gateway: MessagingGatewaySupport,
  * @author Artem Bilan
  */
 fun integrationFlow(gatewaySpec: MessagingGatewaySpec<*, *>,
-					@BuilderInference flow: KotlinIntegrationFlowDefinition.() -> Unit) =
+					flow: KotlinIntegrationFlowDefinition.() -> Unit) =
 		buildIntegrationFlow(IntegrationFlows.from(gatewaySpec), flow)
 
 /**
@@ -147,7 +145,7 @@ fun integrationFlow(gatewaySpec: MessagingGatewaySpec<*, *>,
  * @author Artem Bilan
  */
 fun integrationFlow(producer: MessageProducerSupport,
-					@BuilderInference flow: KotlinIntegrationFlowDefinition.() -> Unit) =
+					flow: KotlinIntegrationFlowDefinition.() -> Unit) =
 		buildIntegrationFlow(IntegrationFlows.from(producer), flow)
 
 /**
@@ -157,5 +155,5 @@ fun integrationFlow(producer: MessageProducerSupport,
  * @author Artem Bilan
  */
 fun integrationFlow(producerSpec: MessageProducerSpec<*, *>,
-					@BuilderInference flow: KotlinIntegrationFlowDefinition.() -> Unit) =
+					flow: KotlinIntegrationFlowDefinition.() -> Unit) =
 		buildIntegrationFlow(IntegrationFlows.from(producerSpec), flow)

spring-integration-kotlin-dsl/src/test/kotlin/org/springframework/integration/dsl/kotlin/test/KotlinDslTests.kt

@@ -207,8 +207,10 @@ class KotlinDslTests {
 		fun functionFlow() =
 				integrationFlow<Function<String, String>>({ it.beanName("functionGateway") }) {
 					transform<String, String> { it.toUpperCase() }
-					split<String> { p -> p }
-					split<String>({ p -> p }) { it.id("splitterEndpoint") }
+					split<Message<*>> { it.payload }
+					split<String>({ it }) { it.id("splitterEndpoint") }
+					resequence()
+					aggregate { it.id("aggregator").outputProcessor { it.one } }
 				}
 
 		@Bean
@@ -223,43 +225,44 @@ class KotlinDslTests {
 		fun messageSourceFlow() =
 				integrationFlow(MessageProcessorMessageSource { "testSource" },
 						{ it.poller { it.trigger(OnlyOnceTrigger()) } }) {
-					channel { c -> c.queue("fromSupplierQueue") }
+					channel { it.queue("fromSupplierQueue") }
 				}
 
 		@Bean
 		fun messageSourceFlow2() =
 				integrationFlow(MessageProcessorMessageSource { "testSource2" }) {
-					channel { c -> c.queue("fromSupplierQueue2") }
+					channel { it.queue("fromSupplierQueue2") }
 				}
 
 		@Bean
 		fun fixedSubscriberFlow() =
 				integrationFlow("fixedSubscriberInput", true) {
-					logAndReply(LoggingHandler.Level.WARN)
+					log<Any>(LoggingHandler.Level.WARN) { it.payload }
+					transform("payload") { it.id("spelTransformer") }
 				}
 
 		@Bean
 		fun flowFromSupplier() =
 				integrationFlow({ "testSupplier" }) {
-					channel { c -> c.queue("testSupplierResult") }
+					channel { it.queue("testSupplierResult") }
 				}
 
 		@Bean
 		fun flowFromSupplier2() =
 				integrationFlow({ "testSupplier2" },
 						{ it.poller { it.trigger(OnlyOnceTrigger()) } }) {
-					filter<Message<Any>> { m -> m.payload is String }
-					channel { c -> c.queue("testSupplierResult2") }
+					filter<Message<*>> { m -> m.payload is String }
+					channel { it.queue("testSupplierResult2") }
 				}
 
 		@Bean
 		fun flowLambda() =
 				integrationFlow {
 					filter<String>({ it === "test" }) { it.id("filterEndpoint") }
-					wireTap(
-							integrationFlow {
-								channel { c -> c.queue("wireTapChannel") }
-							})
+					wireTap {
+						channel { it.queue("wireTapChannel") }
+					}
+					delay("delayGroup") { it.defaultDelay(100) }
 					transform<String, String> { it.toUpperCase() }
 				}