Create SockJS ThreadPoolTaskScheduler extension

Commit 5d2e6f enabled the setRemoveOnCancelPolicy of the SockJS
ScheduledThreadPoolExecutor by default. However that property is only
available in JDK 1.7 or later. This change fixes the issue and
introduces an extension of ThreadPoolTaskScheduler for for use with
SockJS which is necessary in any case since ThreadPoolTaskScheduler
does not expose the underlying ScheduledThreadPoolExecutor otherwise.

Issue: SPR-11918

spring-websocket/src/main/java/org/springframework/web/socket/config/WebSocketNamespaceUtils.java

@@ -16,6 +16,7 @@
 
 package org.springframework.web.socket.config;
 
+import org.springframework.web.socket.sockjs.transport.SockJsThreadPoolTaskScheduler;
 import org.w3c.dom.Element;
 
 import org.springframework.beans.factory.config.BeanDefinition;
@@ -24,18 +25,12 @@ import org.springframework.beans.factory.parsing.BeanComponentDefinition;
 import org.springframework.beans.factory.support.ManagedList;
 import org.springframework.beans.factory.support.RootBeanDefinition;
 import org.springframework.beans.factory.xml.ParserContext;
-import org.springframework.scheduling.concurrent.ThreadPoolTaskScheduler;
 import org.springframework.util.xml.DomUtils;
 import org.springframework.web.socket.server.support.DefaultHandshakeHandler;
 import org.springframework.web.socket.sockjs.transport.TransportHandlingSockJsService;
 import org.springframework.web.socket.sockjs.transport.handler.DefaultSockJsService;
 import org.springframework.web.socket.sockjs.transport.handler.WebSocketTransportHandler;
 
-import java.util.concurrent.ExecutorService;
-import java.util.concurrent.RejectedExecutionHandler;
-import java.util.concurrent.ScheduledThreadPoolExecutor;
-import java.util.concurrent.ThreadFactory;
-
 /**
  * Provides utility methods for parsing common WebSocket XML namespace elements.
  *
@@ -166,16 +161,4 @@ class WebSocketNamespaceUtils {
 		return beans;
 	}
 
-
-	@SuppressWarnings("serial")
-	private static class SockJsThreadPoolTaskScheduler extends ThreadPoolTaskScheduler {
-
-		@Override
-		protected ExecutorService initializeExecutor(ThreadFactory factory, RejectedExecutionHandler handler) {
-			ExecutorService service = super.initializeExecutor(factory, handler);
-			((ScheduledThreadPoolExecutor) service).setRemoveOnCancelPolicy(true);
-			return service;
-		}
-	}
-
 }

spring-websocket/src/main/java/org/springframework/web/socket/config/annotation/WebSocketConfigurationSupport.java

@@ -20,11 +20,7 @@ import org.springframework.context.annotation.Bean;
 import org.springframework.scheduling.concurrent.ThreadPoolTaskScheduler;
 import org.springframework.web.servlet.HandlerMapping;
 import org.springframework.web.servlet.handler.AbstractHandlerMapping;
-
-import java.util.concurrent.ExecutorService;
-import java.util.concurrent.RejectedExecutionHandler;
-import java.util.concurrent.ScheduledThreadPoolExecutor;
-import java.util.concurrent.ThreadFactory;
+import org.springframework.web.socket.sockjs.transport.SockJsThreadPoolTaskScheduler;
 
 /**
  * Configuration support for WebSocket request handling.
@@ -64,15 +60,7 @@ public class WebSocketConfigurationSupport {
 	 */
 	@Bean
 	public ThreadPoolTaskScheduler defaultSockJsTaskScheduler() {
-		@SuppressWarnings("serial")
-		ThreadPoolTaskScheduler scheduler = new ThreadPoolTaskScheduler() {
-			@Override
-			protected ExecutorService initializeExecutor(ThreadFactory factory, RejectedExecutionHandler handler) {
-				ExecutorService service = super.initializeExecutor(factory, handler);
-				((ScheduledThreadPoolExecutor) service).setRemoveOnCancelPolicy(true);
-				return service;
-			}
-		};
+		ThreadPoolTaskScheduler scheduler = new SockJsThreadPoolTaskScheduler();
 		scheduler.setThreadNamePrefix("SockJS-");
 		return scheduler;
 	}

spring-websocket/src/main/java/org/springframework/web/socket/config/annotation/WebSocketMessageBrokerConfigurationSupport.java

@@ -17,20 +17,16 @@
 package org.springframework.web.socket.config.annotation;
 
 import java.util.Collections;
-import java.util.concurrent.ExecutorService;
-import java.util.concurrent.RejectedExecutionHandler;
-import java.util.concurrent.ScheduledThreadPoolExecutor;
-import java.util.concurrent.ThreadFactory;
 
 import org.springframework.beans.factory.config.CustomScopeConfigurer;
 import org.springframework.context.annotation.Bean;
 import org.springframework.messaging.simp.SimpSessionScope;
 import org.springframework.messaging.simp.config.AbstractMessageBrokerConfiguration;
-import org.springframework.messaging.simp.user.UserSessionRegistry;
 import org.springframework.scheduling.concurrent.ThreadPoolTaskScheduler;
 import org.springframework.web.servlet.HandlerMapping;
 import org.springframework.web.socket.WebSocketHandler;
 import org.springframework.web.socket.messaging.SubProtocolWebSocketHandler;
+import org.springframework.web.socket.sockjs.transport.SockJsThreadPoolTaskScheduler;
 
 /**
  * Extends {@link AbstractMessageBrokerConfiguration} and adds configuration for
@@ -100,16 +96,7 @@ public abstract class WebSocketMessageBrokerConfigurationSupport extends Abstrac
 	 */
 	@Bean
 	public ThreadPoolTaskScheduler messageBrokerSockJsTaskScheduler() {
-		@SuppressWarnings("serial")
-		ThreadPoolTaskScheduler scheduler = new ThreadPoolTaskScheduler() {
-			@Override
-			protected ExecutorService initializeExecutor(ThreadFactory factory, RejectedExecutionHandler handler) {
-				ExecutorService service = super.initializeExecutor(factory, handler);
-				((ScheduledThreadPoolExecutor) service).setRemoveOnCancelPolicy(true);
-				return service;
-			}
-		};
-		scheduler.setPoolSize(Runtime.getRuntime().availableProcessors());
+		ThreadPoolTaskScheduler scheduler = new SockJsThreadPoolTaskScheduler();
 		scheduler.setThreadNamePrefix("MessageBrokerSockJS-");
 		return scheduler;
 	}

spring-websocket/src/main/java/org/springframework/web/socket/sockjs/transport/SockJsThreadPoolTaskScheduler.java

@@ -0,0 +1,66 @@
+/*
+ * Copyright 2002-2014 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
+ *
+ * http://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.web.socket.sockjs.transport;
+
+import org.springframework.lang.UsesJava7;
+import org.springframework.scheduling.concurrent.ThreadPoolTaskScheduler;
+import org.springframework.util.ClassUtils;
+
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.RejectedExecutionHandler;
+import java.util.concurrent.ScheduledThreadPoolExecutor;
+import java.util.concurrent.ThreadFactory;
+
+/**
+ * An extension of ThreadPoolTaskScheduler optimized for managing a large number
+ * of task, e.g. setting he pool size to the number of available processors and
+ * setting the setRemoveOnCancelPolicy property of
+ * {@link java.util.concurrent.ScheduledThreadPoolExecutor} available in JDK 1.7
+ * or higher in order to avoid keeping cancelled tasks around.
+ *
+ * @author Rossen Stoyanchev
+ * @since 4.1
+ */
+@SuppressWarnings("serial")
+public class SockJsThreadPoolTaskScheduler extends ThreadPoolTaskScheduler {
+
+	// Check for setRemoveOnCancelPolicy method - available on JDK 7 and higher
+	private static boolean hasRemoveOnCancelPolicyMethod = ClassUtils.hasMethod(
+			ScheduledThreadPoolExecutor.class, "setRemoveOnCancelPolicy", Boolean.class);
+
+
+	public SockJsThreadPoolTaskScheduler() {
+		setThreadNamePrefix("SockJS-");
+		setPoolSize(Runtime.getRuntime().availableProcessors());
+	}
+
+
+	@Override
+	protected ExecutorService initializeExecutor(ThreadFactory factory, RejectedExecutionHandler handler) {
+		ExecutorService service = super.initializeExecutor(factory, handler);
+		configureRemoveOnCancelPolicy((ScheduledThreadPoolExecutor) service);
+		return service;
+	}
+
+	@UsesJava7 // guard setting removeOnCancelPolicy (safe with 1.6 due to hasRemoveOnCancelPolicyMethod check)
+	private void configureRemoveOnCancelPolicy(ScheduledThreadPoolExecutor service) {
+		if (hasRemoveOnCancelPolicyMethod) {
+			service.setRemoveOnCancelPolicy(true);
+		}
+	}
+
+}