Restore server.jetty.threads.max property for Jetty's virtual thread pool

Closes gh-48982

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

@@ -1434,8 +1434,7 @@ public class ServerProperties {
 			private Integer selectors = -1;
 
 			/**
-			 * Maximum number of threads. Doesn't have an effect if virtual threads are
-			 * enabled.
+			 * Maximum number of threads.
 			 */
 			private Integer max = 200;
 

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

@@ -83,16 +83,21 @@ public class EmbeddedWebServerFactoryCustomizerAutoConfiguration {
 	@ConditionalOnClass({ Server.class, Loader.class, WebAppContext.class })
 	public static class JettyWebServerFactoryCustomizerConfiguration {
 
+		private final ServerProperties serverProperties;
+
+		JettyWebServerFactoryCustomizerConfiguration(ServerProperties serverProperties) {
+			this.serverProperties = serverProperties;
+		}
+
 		@Bean
-		public JettyWebServerFactoryCustomizer jettyWebServerFactoryCustomizer(Environment environment,
-				ServerProperties serverProperties) {
-			return new JettyWebServerFactoryCustomizer(environment, serverProperties);
+		public JettyWebServerFactoryCustomizer jettyWebServerFactoryCustomizer(Environment environment) {
+			return new JettyWebServerFactoryCustomizer(environment, this.serverProperties);
 		}
 
 		@Bean
 		@ConditionalOnThreading(Threading.VIRTUAL)
 		JettyVirtualThreadsWebServerFactoryCustomizer jettyVirtualThreadsWebServerFactoryCustomizer() {
-			return new JettyVirtualThreadsWebServerFactoryCustomizer();
+			return new JettyVirtualThreadsWebServerFactoryCustomizer(this.serverProperties);
 		}
 
 	}

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

@@ -20,6 +20,7 @@ import org.eclipse.jetty.util.VirtualThreads;
 import org.eclipse.jetty.util.thread.VirtualThreadPool;
 
 import org.springframework.boot.autoconfigure.web.ServerProperties;
+import org.springframework.boot.autoconfigure.web.ServerProperties.Jetty.Threads;
 import org.springframework.boot.web.embedded.jetty.ConfigurableJettyWebServerFactory;
 import org.springframework.boot.web.server.WebServerFactoryCustomizer;
 import org.springframework.core.Ordered;
@@ -35,18 +36,24 @@ import org.springframework.util.Assert;
 public class JettyVirtualThreadsWebServerFactoryCustomizer
 		implements WebServerFactoryCustomizer<ConfigurableJettyWebServerFactory>, Ordered {
 
-	public JettyVirtualThreadsWebServerFactoryCustomizer() {
+	private final ServerProperties serverProperties;
 
+	/**
+	 * Create a new JettyVirtualThreadsWebServerFactoryCustomizer.
+	 * @deprecated since 3.5.11 for removal in 4.2.0 in favor of
+	 * {@link #JettyVirtualThreadsWebServerFactoryCustomizer(ServerProperties)}
+	 */
+	@Deprecated(since = "3.5.11", forRemoval = true)
+	public JettyVirtualThreadsWebServerFactoryCustomizer() {
+		this(null);
 	}
 
 	/**
 	 * Create a new JettyVirtualThreadsWebServerFactoryCustomizer.
-	 * @param serverProperties server properties
-	 * @deprecated since 3.4.12 for removal in 4.0.0 in favor of
-	 * {@link JettyVirtualThreadsWebServerFactoryCustomizer}.
+	 * @param serverProperties the server properties
 	 */
-	@Deprecated(since = "3.4.12", forRemoval = true)
 	public JettyVirtualThreadsWebServerFactoryCustomizer(ServerProperties serverProperties) {
+		this.serverProperties = serverProperties;
 	}
 
 	@Override
@@ -54,6 +61,11 @@ public class JettyVirtualThreadsWebServerFactoryCustomizer
 		Assert.state(VirtualThreads.areSupported(), "Virtual threads are not supported");
 		VirtualThreadPool virtualThreadPool = new VirtualThreadPool();
 		virtualThreadPool.setName("jetty-");
+		if (this.serverProperties != null) {
+			Threads properties = this.serverProperties.getJetty().getThreads();
+			int maxThreadCount = (properties.getMax() > 0) ? properties.getMax() : 200;
+			virtualThreadPool.setMaxThreads(maxThreadCount);
+		}
 		factory.setThreadPool(virtualThreadPool);
 	}
 

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

@@ -21,6 +21,7 @@ import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.condition.EnabledForJreRange;
 import org.junit.jupiter.api.condition.JRE;
 
+import org.springframework.boot.autoconfigure.web.ServerProperties;
 import org.springframework.boot.web.embedded.jetty.ConfigurableJettyWebServerFactory;
 
 import static org.assertj.core.api.Assertions.assertThat;
@@ -38,13 +39,17 @@ class JettyVirtualThreadsWebServerFactoryCustomizerTests {
 	@Test
 	@EnabledForJreRange(min = JRE.JAVA_21)
 	void shouldConfigureVirtualThreads() {
-		JettyVirtualThreadsWebServerFactoryCustomizer customizer = new JettyVirtualThreadsWebServerFactoryCustomizer();
+		ServerProperties serverProperties = new ServerProperties();
+		serverProperties.getJetty().getThreads().setMax(100);
+		JettyVirtualThreadsWebServerFactoryCustomizer customizer = new JettyVirtualThreadsWebServerFactoryCustomizer(
+				serverProperties);
 		ConfigurableJettyWebServerFactory factory = mock(ConfigurableJettyWebServerFactory.class);
 		customizer.customize(factory);
 		then(factory).should().setThreadPool(assertArg((threadPool) -> {
 			assertThat(threadPool).isInstanceOf(VirtualThreadPool.class);
 			VirtualThreadPool virtualThreadPool = (VirtualThreadPool) threadPool;
 			assertThat(virtualThreadPool.getName()).isEqualTo("jetty-");
+			assertThat(virtualThreadPool.getMaxThreads()).isEqualTo(100);
 		}));
 	}