Configuration options for virtual threads (on JDK 21)

VirtualThreadDelegate built on JDK 21 for multi-release jar.
Includes dedicated VirtualThreadTaskExecutor as lean option.
Includes setVirtualThreads flag on SimpleAsyncTaskExecutor.
Includes additional default methods on AsyncTaskExecutor.

Closes gh-30241

Author: jhoeller

build.gradle

@@ -10,6 +10,7 @@ plugins {
 	id 'com.github.johnrengelman.shadow' version '8.1.1' apply false
 	id 'de.undercouch.download' version '5.4.0'
 	id 'me.champeau.jmh' version '0.7.0' apply false
+	id 'me.champeau.mrjar' version '0.1.1'
 }
 
 ext {

ci/images/get-jdk-url.sh

@@ -9,7 +9,7 @@ case "$1" in
 		echo "https://github.com/bell-sw/Liberica/releases/download/20.0.1+10/bellsoft-jdk20.0.1+10-linux-amd64.tar.gz"
 	;;
   java21)
-    echo "https://download.java.net/java/early_access/jdk21/18/GPL/openjdk-21-ea+18_linux-x64_bin.tar.gz"
+    echo "https://download.java.net/java/early_access/jdk21/20/GPL/openjdk-21-ea+20_linux-x64_bin.tar.gz"
   ;;
 	*)
 		echo $"Unknown java version"

spring-context-support/src/main/java/org/springframework/scheduling/quartz/SimpleThreadPoolTaskExecutor.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2022 the original author or authors.
+ * Copyright 2002-2023 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.
@@ -77,12 +77,6 @@ public void execute(Runnable task) {
 		}
 	}
 
-	@Deprecated
-	@Override
-	public void execute(Runnable task, long startTimeout) {
-		execute(task);
-	}
-
 	@Override
 	public Future<?> submit(Runnable task) {
 		FutureTask<Object> future = new FutureTask<>(task, null);

spring-context/src/main/java/org/springframework/scheduling/concurrent/ThreadPoolTaskExecutor.java

@@ -364,12 +364,6 @@ public void execute(Runnable task) {
 		}
 	}
 
-	@Deprecated
-	@Override
-	public void execute(Runnable task, long startTimeout) {
-		execute(task);
-	}
-
 	@Override
 	public Future<?> submit(Runnable task) {
 		ExecutorService executor = getThreadPoolExecutor();

spring-context/src/main/java/org/springframework/scheduling/concurrent/ThreadPoolTaskScheduler.java

@@ -282,12 +282,6 @@ public void execute(Runnable task) {
 		}
 	}
 
-	@Deprecated
-	@Override
-	public void execute(Runnable task, long startTimeout) {
-		execute(task);
-	}
-
 	@Override
 	public Future<?> submit(Runnable task) {
 		ExecutorService executor = getScheduledExecutor();

spring-core/spring-core.gradle

@@ -1,15 +1,25 @@
 import com.github.jengelman.gradle.plugins.shadow.tasks.ShadowJar
 import org.springframework.build.shadow.ShadowSource
 
+plugins {
+	id 'me.champeau.mrjar'
+}
+
 description = "Spring Core"
 
 apply plugin: "kotlin"
 apply plugin: "kotlinx-serialization"
 
+multiRelease {
+	targetVersions 17, 21
+}
+
 def javapoetVersion = "1.13.0"
 def objenesisVersion = "3.3"
 
 configurations {
+	java21Api.extendsFrom(api)
+	java21Implementation.extendsFrom(implementation)
 	javapoet
 	objenesis
 	graalvm

spring-core/src/main/java/org/springframework/core/task/AsyncTaskExecutor.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2022 the original author or authors.
+ * Copyright 2002-2023 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.
@@ -19,6 +19,7 @@
 import java.util.concurrent.Callable;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.Future;
+import java.util.concurrent.FutureTask;
 
 import org.springframework.util.concurrent.FutureUtils;
 
@@ -60,6 +61,8 @@ public interface AsyncTaskExecutor extends TaskExecutor {
 
 	/**
 	 * Execute the given {@code task}.
+	 * <p>As of 6.1, this method comes with a default implementation that simply
+	 * delegates to {@link #execute(Runnable)}, ignoring the timeout completely.
 	 * @param task the {@code Runnable} to execute (never {@code null})
 	 * @param startTimeout the time duration (milliseconds) within which the task is
 	 * supposed to start. This is intended as a hint to the executor, allowing for
@@ -72,27 +75,41 @@ public interface AsyncTaskExecutor extends TaskExecutor {
 	 * @deprecated as of 5.3.16 since the common executors do not support start timeouts
 	 */
 	@Deprecated
-	void execute(Runnable task, long startTimeout);
+	default void execute(Runnable task, long startTimeout) {
+		execute(task);
+	}
 
 	/**
 	 * Submit a Runnable task for execution, receiving a Future representing that task.
 	 * The Future will return a {@code null} result upon completion.
+	 * <p>As of 6.1, this method comes with a default implementation that delegates
+	 * to {@link #execute(Runnable)}.
 	 * @param task the {@code Runnable} to execute (never {@code null})
 	 * @return a Future representing pending completion of the task
 	 * @throws TaskRejectedException if the given task was not accepted
 	 * @since 3.0
 	 */
-	Future<?> submit(Runnable task);
+	default Future<?> submit(Runnable task) {
+		FutureTask<Object> future = new FutureTask<>(task, null);
+		execute(future);
+		return future;
+	}
 
 	/**
 	 * Submit a Callable task for execution, receiving a Future representing that task.
 	 * The Future will return the Callable's result upon completion.
+	 * <p>As of 6.1, this method comes with a default implementation that delegates
+	 * to {@link #execute(Runnable)}.
 	 * @param task the {@code Callable} to execute (never {@code null})
 	 * @return a Future representing pending completion of the task
 	 * @throws TaskRejectedException if the given task was not accepted
 	 * @since 3.0
 	 */
-	<T> Future<T> submit(Callable<T> task);
+	default <T> Future<T> submit(Callable<T> task) {
+		FutureTask<T> future = new FutureTask<>(task);
+		execute(future, TIMEOUT_INDEFINITE);
+		return future;
+	}
 
 	/**
 	 * Submit a {@code Runnable} task for execution, receiving a {@code CompletableFuture}

spring-core/src/main/java/org/springframework/core/task/SimpleAsyncTaskExecutor.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2022 the original author or authors.
+ * Copyright 2002-2023 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.
@@ -66,6 +66,9 @@ public class SimpleAsyncTaskExecutor extends CustomizableThreadCreator
 	/** Internal concurrency throttle used by this executor. */
 	private final ConcurrencyThrottleAdapter concurrencyThrottle = new ConcurrencyThrottleAdapter();
 
+	@Nullable
+	private VirtualThreadDelegate virtualThreadDelegate;
+
 	@Nullable
 	private ThreadFactory threadFactory;
 
@@ -97,6 +100,16 @@ public SimpleAsyncTaskExecutor(ThreadFactory threadFactory) {
 	}
 
 
+	/**
+	 * Switch this executor to virtual threads. Requires Java 21 or higher.
+	 * <p>The default is {@code false}, indicating platform threads.
+	 * Set this flag to {@code true} in order to create virtual threads instead.
+	 * @since 6.1
+	 */
+	public void setVirtualThreads(boolean virtual) {
+		this.virtualThreadDelegate = (virtual ? new VirtualThreadDelegate() : null);
+	}
+
 	/**
 	 * Specify an external factory to use for creating new Threads,
 	 * instead of relying on the local properties of this executor.
@@ -238,11 +251,16 @@ public <T> ListenableFuture<T> submitListenable(Callable<T> task) {
 	 * Template method for the actual execution of a task.
 	 * <p>The default implementation creates a new Thread and starts it.
 	 * @param task the Runnable to execute
+	 * @see #setVirtualThreads
 	 * @see #setThreadFactory
 	 * @see #createThread
 	 * @see java.lang.Thread#start()
 	 */
 	protected void doExecute(Runnable task) {
+		if (this.virtualThreadDelegate != null) {
+			this.virtualThreadDelegate.startVirtualThread(nextThreadName(), task);
+		}
+
 		Thread thread = (this.threadFactory != null ? this.threadFactory.newThread(task) : createThread(task));
 		thread.start();
 	}

spring-core/src/main/java/org/springframework/core/task/VirtualThreadDelegate.java

@@ -0,0 +1,47 @@
+/*
+ * Copyright 2002-2023 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.task;
+
+import java.util.concurrent.ThreadFactory;
+
+/**
+ * Internal delegate for virtual thread handling on JDK 21.
+ * This is a dummy version for reachability on JDK <21.
+ *
+ * @author Juergen Hoeller
+ * @since 6.1
+ * @see VirtualThreadTaskExecutor
+ */
+class VirtualThreadDelegate {
+
+	public VirtualThreadDelegate() {
+		throw new UnsupportedOperationException("Virtual threads not supported on JDK <21");
+	}
+
+	public ThreadFactory virtualThreadFactory() {
+		throw new UnsupportedOperationException();
+	}
+
+	public ThreadFactory virtualThreadFactory(String threadNamePrefix) {
+		throw new UnsupportedOperationException();
+	}
+
+	public Thread startVirtualThread(String name, Runnable task) {
+		throw new UnsupportedOperationException();
+	}
+
+}

spring-core/src/main/java/org/springframework/core/task/VirtualThreadTaskExecutor.java

@@ -0,0 +1,67 @@
+/*
+ * Copyright 2002-2023 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.task;
+
+import java.util.concurrent.ThreadFactory;
+
+/**
+ * A {@link TaskExecutor} implementation based on virtual threads in JDK 21+.
+ * The only configuration option is a thread name prefix.
+ *
+ * <p>For additional features such as concurrency limiting or task decoration,
+ * consider using {@link SimpleAsyncTaskExecutor#setVirtualThreads} instead.
+ *
+ * @author Juergen Hoeller
+ * @since 6.1
+ * @see SimpleAsyncTaskExecutor
+ */
+public class VirtualThreadTaskExecutor implements AsyncTaskExecutor {
+
+	private final ThreadFactory virtualThreadFactory;
+
+
+	/**
+	 * Create a new {@code VirtualThreadTaskExecutor} without thread naming.
+	 */
+	public VirtualThreadTaskExecutor() {
+		this.virtualThreadFactory = new VirtualThreadDelegate().virtualThreadFactory();
+	}
+
+	/**
+	 * Create a new {@code VirtualThreadTaskExecutor} with thread names based
+	 * on the given thread name prefix followed by a counter (e.g. "test-0").
+	 * @param threadNamePrefix the prefix for thread names (e.g. "test-")
+	 */
+	public VirtualThreadTaskExecutor(String threadNamePrefix) {
+		this.virtualThreadFactory = new VirtualThreadDelegate().virtualThreadFactory(threadNamePrefix);
+	}
+
+
+	/**
+	 * Return the underlying virtual {@link ThreadFactory}.
+	 * Can also be used for custom thread creation elsewhere.
+	 */
+	public final ThreadFactory getVirtualThreadFactory() {
+		return this.virtualThreadFactory;
+	}
+
+	@Override
+	public void execute(Runnable task) {
+		this.virtualThreadFactory.newThread(task).start();
+	}
+
+}

spring-core/src/main/java/org/springframework/core/task/support/TaskExecutorAdapter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2022 the original author or authors.
+ * Copyright 2002-2023 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.
@@ -98,12 +98,6 @@ public void execute(Runnable task) {
 		}
 	}
 
-	@Deprecated
-	@Override
-	public void execute(Runnable task, long startTimeout) {
-		execute(task);
-	}
-
 	@Override
 	public Future<?> submit(Runnable task) {
 		try {

spring-core/src/main/java21/org/springframework/core/task/VirtualThreadDelegate.java

@@ -0,0 +1,45 @@
+/*
+ * Copyright 2002-2023 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.task;
+
+import java.util.concurrent.ThreadFactory;
+
+/**
+ * Internal delegate for virtual thread handling on JDK 21.
+ * This is the actual version compiled against JDK 21.
+ *
+ * @author Juergen Hoeller
+ * @since 6.1
+ * @see VirtualThreadTaskExecutor
+ */
+class VirtualThreadDelegate {
+
+	private final Thread.Builder threadBuilder = Thread.ofVirtual();
+
+	public ThreadFactory virtualThreadFactory() {
+		return this.threadBuilder.factory();
+	}
+
+	public ThreadFactory virtualThreadFactory(String threadNamePrefix) {
+		return this.threadBuilder.name(threadNamePrefix, 0).factory();
+	}
+
+	public Thread startVirtualThread(String name, Runnable task) {
+		return this.threadBuilder.name(name).start(task);
+	}
+
+}

spring-core/src/test/java/org/springframework/core/io/ClassPathResourceTests.java

@@ -214,7 +214,7 @@ void convertsToAbsolutePathForClassRelativeAccess() {
 
 	@Test
 	void directoryNotReadable() throws Exception {
-		Resource fileDir = new ClassPathResource("org/springframework/core");
+		Resource fileDir = new ClassPathResource("example/type");
 		assertThat(fileDir.getURL()).asString().startsWith("file:");
 		assertThat(fileDir.exists()).isTrue();
 		assertThat(fileDir.isReadable()).isFalse();