Introduce spring-core-coroutines module

This commit introduces the spring-core-coroutines module
in order to avoid referencing Kotlin code from Java one,
which is currently not supported by Eclipse.

During the build, spring-core-coroutines is merged into
spring-core, so this change is expected to have no impact
for end users.

This module contains functions accessible from Java via
the CoroutinesUtils class to adapt Coroutines and Deferred
instances to and from Mono.

See gh-19975

build.gradle

@@ -25,7 +25,7 @@ ext {
 	linkScmDevConnection = "scm:git:ssh://git@github.com:spring-projects/spring-framework.git"
 
 	moduleProjects = subprojects.findAll {
-		!it.name.equals("spring-build-src") && !it.name.equals("spring-framework-bom")
+		!it.name.equals("spring-build-src") && !it.name.equals("spring-framework-bom") && !it.name.equals("spring-core-coroutines")
 	}
 
 	aspectjVersion       = "1.9.2"

settings.gradle

@@ -5,6 +5,7 @@ include "spring-context"
 include "spring-context-support"
 include "spring-context-indexer"
 include "spring-core"
+include "spring-core-coroutines"
 include "spring-expression"
 include "spring-instrument"
 include "spring-jcl"

spring-core-coroutines/spring-core-coroutines.gradle

@@ -0,0 +1,9 @@
+description = "Spring Core Coroutines support"
+
+dependencies {
+	compile("org.jetbrains.kotlin:kotlin-reflect:${kotlinVersion}")
+	compile("org.jetbrains.kotlin:kotlin-stdlib:${kotlinVersion}")
+	compile("io.projectreactor:reactor-core")
+	compile("org.jetbrains.kotlinx:kotlinx-coroutines-core:${coroutinesVersion}")
+	compile("org.jetbrains.kotlinx:kotlinx-coroutines-reactor:${coroutinesVersion}")
+}

spring-core-coroutines/src/main/kotlin/org/springframework/core/CoroutinesUtils.kt

@@ -14,10 +14,16 @@
  * limitations under the License.
  */
 
-package org.springframework.web.reactive.result.method
+@file:JvmName("CoroutinesUtils")
+package org.springframework.core
 
+import kotlinx.coroutines.Deferred
 import kotlinx.coroutines.GlobalScope
+import kotlinx.coroutines.async
+import kotlinx.coroutines.reactive.awaitFirstOrNull
+
 import kotlinx.coroutines.reactor.mono
+import reactor.core.publisher.Mono
 import reactor.core.publisher.onErrorMap
 import java.lang.reflect.InvocationTargetException
 import java.lang.reflect.Method
@@ -25,7 +31,23 @@ import kotlin.reflect.full.callSuspend
 import kotlin.reflect.jvm.kotlinFunction
 
 /**
- * Invoke an handler method converting suspending method to {@link Mono} if necessary.
+ * Convert a [Deferred] instance to a [Mono] one.
+ *
+ * @author Sebastien Deleuze
+ * @since 5.2
+ */
+internal fun <T: Any> deferredToMono(source: Deferred<T>) = GlobalScope.mono { source.await() }
+
+/**
+ * Convert a [Mono] instance to a [Deferred] one.
+ *
+ * @author Sebastien Deleuze
+ * @since 5.2
+ */
+internal fun <T: Any> monoToDeferred(source: Mono<T>) = GlobalScope.async { source.awaitFirstOrNull() }
+
+/**
+ * Invoke an handler method converting suspending method to [Mono] if necessary.
  *
  * @author Sebastien Deleuze
  * @since 5.2
@@ -40,4 +62,4 @@ internal fun invokeHandlerMethod(method: Method, bean: Any, vararg args: Any?):
 	else {
 		function.call(bean, *args)
 	}
-}
+}

spring-core/spring-core.gradle

@@ -17,6 +17,9 @@ configurations {
 	jarjar
 	cglib
 	objenesis
+	coroutines {
+		transitive = false
+	}
 }
 
 task cglibRepackJar(type: Jar) { repackJar ->
@@ -65,10 +68,12 @@ dependencies {
 	cglib("cglib:cglib:${cglibVersion}@jar")
 	objenesis("org.objenesis:objenesis:${objenesisVersion}@jar")
 	jarjar("org.pantsbuild:jarjar:1.7.2")
+	coroutines(project(":spring-core-coroutines"))
 
 	compile(files(cglibRepackJar))
 	compile(files(objenesisRepackJar))
 	compile(project(":spring-jcl"))
+	compileOnly(project(":spring-core-coroutines"))
 	optional("net.sf.jopt-simple:jopt-simple:5.0.4")
 	optional("org.aspectj:aspectjweaver:${aspectjVersion}")
 	optional("org.jetbrains.kotlin:kotlin-reflect:${kotlinVersion}")
@@ -78,8 +83,6 @@ dependencies {
 	optional("io.reactivex:rxjava-reactive-streams:${rxjavaAdapterVersion}")
 	optional("io.reactivex.rxjava2:rxjava:${rxjava2Version}")
 	optional("io.netty:netty-buffer")
-	optional("org.jetbrains.kotlinx:kotlinx-coroutines-core:${coroutinesVersion}")
-	optional("org.jetbrains.kotlinx:kotlinx-coroutines-reactor:${coroutinesVersion}")
 	testCompile("io.projectreactor:reactor-test")
 	testCompile("org.apache.tomcat.embed:tomcat-embed-core:${tomcatVersion}")
 	testCompile("org.xmlunit:xmlunit-matchers:2.6.2")
@@ -87,6 +90,7 @@ dependencies {
 	testCompile("com.fasterxml.woodstox:woodstox-core:5.2.0") {
 		exclude group: "stax", module: "stax-api"
 	}
+	testCompile(project(":spring-core-coroutines"))
 }
 
 jar {
@@ -107,4 +111,6 @@ jar {
 	from(zipTree(objenesisRepackJar.archivePath)) {
 		include "org/springframework/objenesis/**"
 	}
+
+	from { configurations.coroutines.collect { it.isDirectory() ? it : zipTree(it) } }
 }

spring-core/src/main/java/org/springframework/core/ReactiveAdapterRegistry.java

@@ -25,6 +25,8 @@ import java.util.function.Function;
 
 import io.reactivex.BackpressureStrategy;
 import io.reactivex.Flowable;
+import kotlinx.coroutines.CompletableDeferredKt;
+import kotlinx.coroutines.Deferred;
 import org.reactivestreams.Publisher;
 import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
@@ -93,7 +95,7 @@ public class ReactiveAdapterRegistry {
 
 		// Coroutines
 		if (ClassUtils.isPresent("kotlinx.coroutines.Deferred", classLoader)) {
-			CoroutinesRegistrarKt.registerAdapter(this);
+			new CoroutinesRegistrar().registerAdapters(this);
 		}
 	}
 
@@ -324,4 +326,16 @@ public class ReactiveAdapterRegistry {
 		}
 	}
 
+	private static class CoroutinesRegistrar {
+
+		@SuppressWarnings("KotlinInternalInJava")
+		void registerAdapters(ReactiveAdapterRegistry registry) {
+			registry.registerReactiveType(
+					ReactiveTypeDescriptor.singleOptionalValue(Deferred.class, () -> CompletableDeferredKt.CompletableDeferred(null)),
+					source -> CoroutinesUtils.deferredToMono((Deferred<?>) source),
+					source -> CoroutinesUtils.monoToDeferred(Mono.from(source)));
+		}
+
+	}
+
 }

spring-core/src/main/kotlin/org/springframework/core/CoroutinesRegistrar.kt

@@ -1,38 +0,0 @@
-/*
- * Copyright 2002-2019 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.core
-
-import kotlinx.coroutines.Deferred
-import kotlinx.coroutines.GlobalScope
-import kotlinx.coroutines.async
-import kotlinx.coroutines.reactive.awaitFirstOrNull
-import kotlinx.coroutines.reactor.mono
-import reactor.core.publisher.toMono
-
-/**
- * Register Reactive adapters for Coroutines types.
- *
- * @author Sebastien Deleuze
- * @since 5.2
- */
-internal fun registerAdapter(registry: ReactiveAdapterRegistry) {
-	registry.registerReactiveType(
-			ReactiveTypeDescriptor.singleOptionalValue(Deferred::class.java) { GlobalScope.async {} },
-			{ source -> GlobalScope.mono { (source as Deferred<*>).await() }},
-			{ source -> GlobalScope.async { source.toMono().awaitFirstOrNull() } }
-	)
-}

spring-webflux/spring-webflux.gradle

@@ -13,6 +13,7 @@ dependencies {
 	compile(project(":spring-core"))
 	compile(project(":spring-web"))
 	compile("io.projectreactor:reactor-core")
+	compileOnly(project(":spring-core-coroutines"))
 	optional(project(":spring-context"))
 	optional(project(":spring-context-support"))  // for FreeMarker support
 	optional("javax.servlet:javax.servlet-api:4.0.1")
@@ -55,6 +56,7 @@ dependencies {
 	testCompile("org.eclipse.jetty:jetty-reactive-httpclient:1.0.2")
 	testCompile("com.squareup.okhttp3:mockwebserver:3.14.0")
 	testCompile("org.jetbrains.kotlin:kotlin-script-runtime:${kotlinVersion}")
+	testCompile(project(":spring-core-coroutines"))
 	testRuntime("org.jetbrains.kotlin:kotlin-script-util:${kotlinVersion}")
 	testRuntime("org.jetbrains.kotlin:kotlin-compiler:${kotlinVersion}")
 	testRuntime("org.jruby:jruby:9.2.6.0")

spring-webflux/src/main/java/org/springframework/web/reactive/result/method/InvocableHandlerMethod.java

@@ -26,6 +26,7 @@ import java.util.stream.Stream;
 
 import reactor.core.publisher.Mono;
 
+import org.springframework.core.CoroutinesUtils;
 import org.springframework.core.DefaultParameterNameDiscoverer;
 import org.springframework.core.KotlinDetector;
 import org.springframework.core.MethodParameter;
@@ -131,6 +132,7 @@ public class InvocableHandlerMethod extends HandlerMethod {
 	 * @param providedArgs optional list of argument values to match by type
 	 * @return a Mono with a {@link HandlerResult}.
 	 */
+	@SuppressWarnings("KotlinInternalInJava")
 	public Mono<HandlerResult> invoke(
 			ServerWebExchange exchange, BindingContext bindingContext, Object... providedArgs) {
 
@@ -140,7 +142,7 @@ public class InvocableHandlerMethod extends HandlerMethod {
 				ReflectionUtils.makeAccessible(getBridgedMethod());
 				Method method = getBridgedMethod();
 				if (KotlinDetector.isKotlinReflectPresent() && KotlinDetector.isKotlinType(method.getDeclaringClass())) {
-					value = InvocableHandlerMethodKt.invokeHandlerMethod(method, getBean(), args);
+					value = CoroutinesUtils.invokeHandlerMethod(method, getBean(), args);
 				}
 				else {
 					value = method.invoke(getBean(), args);