Add support for Coroutines transactions

This commit adds Coroutines extensions for
TransactionalOperator.transactional that accept suspending lambda or
Kotlin Flow parameters.

@transactional on suspending functions is not supported yet, gh-23575
has been created for that purpose.

Closes gh-22915

Author: sdeleuze

spring-tx/spring-tx.gradle

@@ -1,17 +1,24 @@
 description = "Spring Transaction"
 
+apply plugin: "kotlin"
+
 dependencies {
 	compile(project(":spring-beans"))
 	compile(project(":spring-core"))
 	optional(project(":spring-aop"))
 	optional(project(":spring-context"))  // for JCA, @EnableTransactionManagement
+	optional(project(":kotlin-coroutines"))
 	optional("javax.ejb:javax.ejb-api")
 	optional("javax.interceptor:javax.interceptor-api")
 	optional("javax.resource:javax.resource-api")
 	optional("javax.transaction:javax.transaction-api")
 	optional("com.ibm.websphere:uow")
 	optional("io.projectreactor:reactor-core")
 	optional("io.vavr:vavr")
+	optional("org.jetbrains.kotlin:kotlin-reflect")
+	optional("org.jetbrains.kotlin:kotlin-stdlib")
+	optional("org.jetbrains.kotlinx:kotlinx-coroutines-core")
+	optional("org.jetbrains.kotlinx:kotlinx-coroutines-reactor")
 	testCompile("org.aspectj:aspectjweaver")
 	testCompile("org.codehaus.groovy:groovy")
 	testCompile("org.eclipse.persistence:javax.persistence")

spring-tx/src/main/java/org/springframework/transaction/interceptor/TransactionAspectSupport.java

@@ -21,6 +21,8 @@
 import java.util.concurrent.ConcurrentMap;
 
 import io.vavr.control.Try;
+import kotlin.reflect.KFunction;
+import kotlin.reflect.jvm.ReflectJvmMapping;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import reactor.core.publisher.Flux;
@@ -30,6 +32,7 @@
 import org.springframework.beans.factory.BeanFactoryAware;
 import org.springframework.beans.factory.InitializingBean;
 import org.springframework.beans.factory.annotation.BeanFactoryAnnotationUtils;
+import org.springframework.core.KotlinDetector;
 import org.springframework.core.NamedThreadLocal;
 import org.springframework.core.ReactiveAdapter;
 import org.springframework.core.ReactiveAdapterRegistry;
@@ -41,6 +44,7 @@
 import org.springframework.transaction.TransactionManager;
 import org.springframework.transaction.TransactionStatus;
 import org.springframework.transaction.TransactionSystemException;
+import org.springframework.transaction.TransactionUsageException;
 import org.springframework.transaction.reactive.TransactionContextManager;
 import org.springframework.transaction.support.CallbackPreferringPlatformTransactionManager;
 import org.springframework.util.Assert;
@@ -322,6 +326,10 @@ protected Object invokeWithinTransaction(Method method, @Nullable Class<?> targe
 			final InvocationCallback invocation) throws Throwable {
 
 		if (this.reactiveAdapterRegistry != null) {
+			if (KotlinDetector.isKotlinType(method.getDeclaringClass()) && KotlinDelegate.isSuspend(method)) {
+				throw new TransactionUsageException("Annotated transactions on suspending functions are not supported," +
+						" use TransactionalOperator.transactional extensions instead.");
+			}
 			ReactiveAdapter adapter = this.reactiveAdapterRegistry.getAdapter(method.getReturnType());
 			if (adapter != null) {
 				return new ReactiveTransactionSupport(adapter).invokeWithinTransaction(method, targetClass, invocation);
@@ -809,6 +817,17 @@ public static Object evaluateTryFailure(Object retVal, TransactionAttribute txAt
 		}
 	}
 
+	/**
+	 * Inner class to avoid a hard dependency on Kotlin at runtime.
+	 */
+	private static class KotlinDelegate {
+
+		static private boolean isSuspend(Method method) {
+			KFunction<?> function = ReflectJvmMapping.getKotlinFunction(method);
+			return function != null && function.isSuspend();
+		}
+	}
+
 
 	/**
 	 * Delegate for Reactor-based management of transactional methods with a

spring-tx/src/main/kotlin/org/springframework/transaction/reactive/TransactionalOperatorExtensions.kt

@@ -0,0 +1,29 @@
+package org.springframework.transaction.reactive
+
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.ExperimentalCoroutinesApi
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.reactive.asFlow
+import kotlinx.coroutines.reactive.awaitFirstOrNull
+import kotlinx.coroutines.reactor.asFlux
+import kotlinx.coroutines.reactor.mono
+
+/**
+ * Coroutines variant of [TransactionalOperator.transactional] with a [Flow] parameter.
+ *
+ * @author Sebastien Deleuze
+ * @since 5.2
+ */
+@ExperimentalCoroutinesApi
+fun <T : Any> TransactionalOperator.transactional(flow: Flow<T>): Flow<T> =
+		transactional(flow.asFlux()).asFlow()
+
+/**
+* Coroutines variant of [TransactionalOperator.transactional] with a suspending lambda
+* parameter.
+*
+* @author Sebastien Deleuze
+* @since 5.2
+*/
+suspend fun <T : Any> TransactionalOperator.transactional(f: suspend () -> T?): T? =
+		transactional(mono(Dispatchers.Unconfined) { f() }).awaitFirstOrNull()

spring-tx/src/test/kotlin/org/springframework/transaction/reactive/TransactionalOperatorExtensionsTests.kt

@@ -0,0 +1,100 @@
+/*
+ * 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.transaction.reactive
+
+import kotlinx.coroutines.ExperimentalCoroutinesApi
+import kotlinx.coroutines.delay
+import kotlinx.coroutines.flow.flow
+import kotlinx.coroutines.flow.toList
+import kotlinx.coroutines.runBlocking
+import org.assertj.core.api.Assertions.assertThat
+import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.fail
+import org.springframework.transaction.support.DefaultTransactionDefinition
+
+class TransactionalOperatorExtensionsTests {
+
+	private val tm = ReactiveTestTransactionManager(false, true)
+
+	@Test
+	fun commitWithSuspendingFunction() {
+		val operator = TransactionalOperator.create(tm, DefaultTransactionDefinition())
+		runBlocking {
+			operator.transactional {
+				delay(1)
+				true
+			}
+		}
+		assertThat(tm.commit).isTrue()
+		assertThat(tm.rollback).isFalse()
+	}
+
+	@Test
+	fun rollbackWithSuspendingFunction() {
+		val operator = TransactionalOperator.create(tm, DefaultTransactionDefinition())
+		runBlocking {
+			try {
+				operator.transactional {
+					delay(1)
+					throw IllegalStateException()
+				}
+			} catch (ex: IllegalStateException) {
+				assertThat(tm.commit).isFalse()
+				assertThat(tm.rollback).isTrue()
+				return@runBlocking
+			}
+			fail("")
+		}
+	}
+
+	@Test
+	@ExperimentalCoroutinesApi
+	fun commitWithFlow() {
+		val operator = TransactionalOperator.create(tm, DefaultTransactionDefinition())
+		val flow = flow {
+			emit(1)
+			emit(2)
+			emit(3)
+			emit(4)
+		}
+		runBlocking {
+			val list = operator.transactional(flow).toList()
+			assertThat(list).hasSize(4)
+		}
+		assertThat(tm.commit).isTrue()
+		assertThat(tm.rollback).isFalse()
+	}
+
+	@Test
+	@ExperimentalCoroutinesApi
+	fun rollbackWithFlow() {
+		val operator = TransactionalOperator.create(tm, DefaultTransactionDefinition())
+		val flow = flow<Int> {
+			delay(1)
+			throw IllegalStateException()
+		}
+		runBlocking {
+			try {
+				operator.transactional(flow).toList()
+			} catch (ex: IllegalStateException) {
+				assertThat(tm.commit).isFalse()
+				assertThat(tm.rollback).isTrue()
+				return@runBlocking
+			}
+		}
+	}
+}

src/docs/asciidoc/languages/kotlin.adoc

@@ -574,6 +574,12 @@ class UserHandler(builder: WebClient.Builder) {
 }
 ----
 
+=== Transactions
+
+Transactions on Coroutines are supported via the programmatic variant of the Reactive
+transaction management provided as of Spring Framework 5.2. `TransactionalOperator.transactional`
+extensions with suspending lambda and Kotlin `Flow` parameter are provided for that purpose.
+
 [[kotlin-spring-projects-in-kotlin]]
 == Spring Projects in Kotlin