Configure Jetty with VirtualThreadPool

Prior to this commit, Spring Boot would auto-configure a
`QueuedThreadPool` on the Jetty embedded server when the virtual threads
option is enabled.

This commit configures instead the dedicated `VirtualThreadPool` that
the Jetty team recommends when Virtual Threads is supported.

Fixes gh-47690

Author: bclozel

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/embedded/JettyVirtualThreadsWebServerFactoryCustomizer.java

@@ -17,7 +17,7 @@
 package org.springframework.boot.autoconfigure.web.embedded;
 
 import org.eclipse.jetty.util.VirtualThreads;
-import org.eclipse.jetty.util.thread.QueuedThreadPool;
+import org.eclipse.jetty.util.thread.VirtualThreadPool;
 
 import org.springframework.boot.autoconfigure.web.ServerProperties;
 import org.springframework.boot.web.embedded.jetty.ConfigurableJettyWebServerFactory;
@@ -29,6 +29,7 @@
  * Activates virtual threads on the {@link ConfigurableJettyWebServerFactory}.
  *
  * @author Moritz Halbritter
+ * @author Brian Clozel
  * @since 3.2.0
  */
 public class JettyVirtualThreadsWebServerFactoryCustomizer
@@ -43,9 +44,9 @@ public JettyVirtualThreadsWebServerFactoryCustomizer(ServerProperties serverProp
 	@Override
 	public void customize(ConfigurableJettyWebServerFactory factory) {
 		Assert.state(VirtualThreads.areSupported(), "Virtual threads are not supported");
-		QueuedThreadPool threadPool = JettyThreadPool.create(this.serverProperties.getJetty().getThreads());
-		threadPool.setVirtualThreadsExecutor(VirtualThreads.getNamedVirtualThreadsExecutor("jetty-"));
-		factory.setThreadPool(threadPool);
+		VirtualThreadPool virtualThreadPool = new VirtualThreadPool();
+		virtualThreadPool.setName("jetty-");
+		factory.setThreadPool(virtualThreadPool);
 	}
 
 	@Override

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/web/embedded/JettyVirtualThreadsWebServerFactoryCustomizerTests.java

@@ -16,13 +16,7 @@
 
 package org.springframework.boot.autoconfigure.web.embedded;
 
-import java.time.Duration;
-import java.util.concurrent.Executor;
-import java.util.concurrent.atomic.AtomicReference;
-
-import org.awaitility.Awaitility;
-import org.eclipse.jetty.util.thread.QueuedThreadPool;
-import org.hamcrest.Matchers;
+import org.eclipse.jetty.util.thread.VirtualThreadPool;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.condition.EnabledForJreRange;
 import org.junit.jupiter.api.condition.JRE;
@@ -51,14 +45,9 @@ void shouldConfigureVirtualThreads() {
 		ConfigurableJettyWebServerFactory factory = mock(ConfigurableJettyWebServerFactory.class);
 		customizer.customize(factory);
 		then(factory).should().setThreadPool(assertArg((threadPool) -> {
-			assertThat(threadPool).isInstanceOf(QueuedThreadPool.class);
-			QueuedThreadPool queuedThreadPool = (QueuedThreadPool) threadPool;
-			Executor executor = queuedThreadPool.getVirtualThreadsExecutor();
-			assertThat(executor).isNotNull();
-			AtomicReference<String> threadName = new AtomicReference<>();
-			executor.execute(() -> threadName.set(Thread.currentThread().getName()));
-			Awaitility.await().atMost(Duration.ofSeconds(1)).untilAtomic(threadName, Matchers.notNullValue());
-			assertThat(threadName.get()).startsWith("jetty-");
+			assertThat(threadPool).isInstanceOf(VirtualThreadPool.class);
+			VirtualThreadPool virtualThreadPool = (VirtualThreadPool) threadPool;
+			assertThat(virtualThreadPool.getName()).isEqualTo("jetty-");
 		}));
 	}