ThreadPoolTaskScheduler allows for setPoolSize changes at runtime

Also exposing "getPoolSize()" and "getActiveCount()" from ThreadPoolTaskScheduler now, analogous to ThreadPoolTaskExecutor.

Issue: SPR-10883

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

 /*
- * Copyright 2002-2012 the original author or authors.
+ * Copyright 2002-2013 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.
@@ -154,9 +154,7 @@ public class ThreadPoolTaskExecutor extends ExecutorConfigurationSupport impleme
 	 * Specify whether to allow core threads to time out. This enables dynamic
 	 * growing and shrinking even in combination with a non-zero queue (since
 	 * the max pool size will only grow once the queue is full).
-	 * <p>Default is "false". Note that this feature is only available on Java 6
-	 * or above. On Java 5, consider switching to the backport-concurrent
-	 * version of ThreadPoolTaskExecutor which also supports this feature.
+	 * <p>Default is "false".
 	 * @see java.util.concurrent.ThreadPoolExecutor#allowCoreThreadTimeOut(boolean)
 	 */
 	public void setAllowCoreThreadTimeOut(boolean allowCoreThreadTimeOut) {
@@ -225,7 +223,11 @@ public class ThreadPoolTaskExecutor extends ExecutorConfigurationSupport impleme
 	 * @see java.util.concurrent.ThreadPoolExecutor#getPoolSize()
 	 */
 	public int getPoolSize() {
-		return getThreadPoolExecutor().getPoolSize();
+		if (this.threadPoolExecutor == null) {
+			// Not initialized yet: assume core pool size.
+			return this.corePoolSize;
+		}
+		return this.threadPoolExecutor.getPoolSize();
 	}
 
 	/**
@@ -233,7 +235,11 @@ public class ThreadPoolTaskExecutor extends ExecutorConfigurationSupport impleme
 	 * @see java.util.concurrent.ThreadPoolExecutor#getActiveCount()
 	 */
 	public int getActiveCount() {
-		return getThreadPoolExecutor().getActiveCount();
+		if (this.threadPoolExecutor == null) {
+			// Not initialized yet: assume no active threads.
+			return 0;
+		}
+		return this.threadPoolExecutor.getActiveCount();
 	}
 
 

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

 /*
- * Copyright 2002-2012 the original author or authors.
+ * Copyright 2002-2013 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.
@@ -62,14 +62,18 @@ public class ThreadPoolTaskScheduler extends ExecutorConfigurationSupport
 	/**
 	 * Set the ScheduledExecutorService's pool size.
 	 * Default is 1.
+	 * <p><b>This setting can be modified at runtime, for example through JMX.</b>
 	 */
 	public void setPoolSize(int poolSize) {
 		Assert.isTrue(poolSize > 0, "'poolSize' must be 1 or higher");
 		this.poolSize = poolSize;
+		if (this.scheduledExecutor instanceof ScheduledThreadPoolExecutor) {
+			((ScheduledThreadPoolExecutor) this.scheduledExecutor).setCorePoolSize(poolSize);
+		}
 	}
 
 	/**
-	 * Provide an {@link ErrorHandler} strategy.
+	 * Set a custom {@link ErrorHandler} strategy.
 	 */
 	public void setErrorHandler(ErrorHandler errorHandler) {
 		Assert.notNull(errorHandler, "'errorHandler' must not be null");
@@ -111,6 +115,47 @@ public class ThreadPoolTaskScheduler extends ExecutorConfigurationSupport
 		return this.scheduledExecutor;
 	}
 
+	/**
+	 * Return the underlying ScheduledThreadPoolExecutor, if available.
+	 * @return the underlying ScheduledExecutorService (never {@code null})
+	 * @throws IllegalStateException if the ThreadPoolTaskScheduler hasn't been initialized yet
+	 * or if the underlying ScheduledExecutorService isn't a ScheduledThreadPoolExecutor
+	 * @see #getScheduledExecutor()
+	 */
+	public ScheduledThreadPoolExecutor getScheduledThreadPoolExecutor() throws IllegalStateException {
+		Assert.state(this.scheduledExecutor instanceof ScheduledThreadPoolExecutor,
+				"No ScheduledThreadPoolExecutor available");
+		return (ScheduledThreadPoolExecutor) this.scheduledExecutor;
+	}
+
+	/**
+	 * Return the current pool size.
+	 * <p>Requires an underlying {@link ScheduledThreadPoolExecutor}.
+	 * @see #getScheduledThreadPoolExecutor()
+	 * @see java.util.concurrent.ScheduledThreadPoolExecutor#getPoolSize()
+	 */
+	public int getPoolSize() {
+		if (this.scheduledExecutor == null) {
+			// Not initialized yet: assume initial pool size.
+			return this.poolSize;
+		}
+		return getScheduledThreadPoolExecutor().getPoolSize();
+	}
+
+	/**
+	 * Return the number of currently active threads.
+	 * <p>Requires an underlying {@link ScheduledThreadPoolExecutor}.
+	 * @see #getScheduledThreadPoolExecutor()
+	 * @see java.util.concurrent.ScheduledThreadPoolExecutor#getActiveCount()
+	 */
+	public int getActiveCount() {
+		if (this.scheduledExecutor == null) {
+			// Not initialized yet: assume no active threads.
+			return 0;
+		}
+		return getScheduledThreadPoolExecutor().getActiveCount();
+	}
+
 
 	// SchedulingTaskExecutor implementation