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

Author: sdeleuze

build.gradle

@@ -25,7 +25,7 @@ ext {
 	linkScmDevConnection = "scm:git:ssh://[email protected]: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-webflux/src/main/kotlin/org/springframework/web/reactive/result/method/InvocableHandlerMethod.kt renamed to spring-core-coroutines/src/main/kotlin/org/springframework/core/CoroutinesUtils.kt

@@ -14,18 +14,40 @@
  * 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
 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}")
@@ -78,15 +83,14 @@ 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")
 	testCompile("javax.xml.bind:jaxb-api:2.3.1")
 	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 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 ReactiveAdapterRegistry() {
 
 		// Coroutines
 		if (ClassUtils.isPresent("kotlinx.coroutines.Deferred", classLoader)) {
-			CoroutinesRegistrarKt.registerAdapter(this);
+			new CoroutinesRegistrar().registerAdapters(this);
 		}
 	}
 
@@ -324,4 +326,16 @@ public <T> Publisher<T> toPublisher(@Nullable Object source) {
 		}
 	}
 
+	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

@@ -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/spring-webflux.gradle

@@ -26,6 +26,7 @@
 
 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 void setReactiveAdapterRegistry(ReactiveAdapterRegistry registry) {
 	 * @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 Mono<HandlerResult> invoke(
 				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);