Defensively use setRemoveOnCancelPolicy for JDK 6 compatibility

Issue: SPR-12238

Author: jhoeller

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

@@ -28,6 +28,7 @@
 import org.springframework.scheduling.support.DelegatingErrorHandlingRunnable;
 import org.springframework.scheduling.support.TaskUtils;
 import org.springframework.util.Assert;
+import org.springframework.util.ClassUtils;
 import org.springframework.util.ObjectUtils;
 
 /**
@@ -67,9 +68,14 @@
 public class ScheduledExecutorFactoryBean extends ExecutorConfigurationSupport
 		implements FactoryBean<ScheduledExecutorService> {
 
+	// ScheduledThreadPoolExecutor.setRemoveOnCancelPolicy(boolean) only available on JDK 1.7+
+	private static final boolean setRemoveOnCancelPolicyAvailable =
+			ClassUtils.hasMethod(ScheduledThreadPoolExecutor.class, "setRemoveOnCancelPolicy", boolean.class);
+
+
 	private int poolSize = 1;
 
-	private Boolean removeOnCancelPolicy;
+	private boolean removeOnCancelPolicy;
 
 	private ScheduledExecutorTask[] scheduledExecutorTasks;
 
@@ -143,8 +149,13 @@ protected ExecutorService initializeExecutor(
 		ScheduledExecutorService executor =
 				createExecutor(this.poolSize, threadFactory, rejectedExecutionHandler);
 
-		if (executor instanceof ScheduledThreadPoolExecutor && this.removeOnCancelPolicy != null) {
-			((ScheduledThreadPoolExecutor) executor).setRemoveOnCancelPolicy(this.removeOnCancelPolicy);
+		if (this.removeOnCancelPolicy) {
+			if (setRemoveOnCancelPolicyAvailable && executor instanceof ScheduledThreadPoolExecutor) {
+				((ScheduledThreadPoolExecutor) executor).setRemoveOnCancelPolicy(true);
+			}
+			else {
+				logger.info("Could not apply remove-on-cancel policy - not a Java 7+ ScheduledThreadPoolExecutor");
+			}
 		}
 
 		// Register specified ScheduledExecutorTasks, if necessary.
@@ -216,6 +227,7 @@ protected Runnable getRunnableToSchedule(ScheduledExecutorTask task) {
 				new DelegatingErrorHandlingRunnable(task.getRunnable(), TaskUtils.LOG_AND_PROPAGATE_ERROR_HANDLER));
 	}
 
+
 	@Override
 	public ScheduledExecutorService getObject() {
 		return this.exposedExecutor;

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

@@ -37,6 +37,7 @@
 import org.springframework.scheduling.Trigger;
 import org.springframework.scheduling.support.TaskUtils;
 import org.springframework.util.Assert;
+import org.springframework.util.ClassUtils;
 import org.springframework.util.ErrorHandler;
 import org.springframework.util.concurrent.ListenableFuture;
 import org.springframework.util.concurrent.ListenableFutureTask;
@@ -57,9 +58,14 @@
 public class ThreadPoolTaskScheduler extends ExecutorConfigurationSupport
 		implements AsyncListenableTaskExecutor, SchedulingTaskExecutor, TaskScheduler {
 
+	// ScheduledThreadPoolExecutor.setRemoveOnCancelPolicy(boolean) only available on JDK 1.7+
+	private static final boolean setRemoveOnCancelPolicyAvailable =
+			ClassUtils.hasMethod(ScheduledThreadPoolExecutor.class, "setRemoveOnCancelPolicy", boolean.class);
+
+
 	private volatile int poolSize = 1;
 
-	private volatile Boolean removeOnCancelPolicy;
+	private volatile boolean removeOnCancelPolicy;
 
 	private volatile ScheduledExecutorService scheduledExecutor;
 
@@ -87,28 +93,36 @@ public void setPoolSize(int poolSize) {
 	@UsesJava7
 	public void setRemoveOnCancelPolicy(boolean removeOnCancelPolicy) {
 		this.removeOnCancelPolicy = removeOnCancelPolicy;
-		if (this.scheduledExecutor instanceof ScheduledThreadPoolExecutor) {
+		if (setRemoveOnCancelPolicyAvailable && this.scheduledExecutor instanceof ScheduledThreadPoolExecutor) {
 			((ScheduledThreadPoolExecutor) this.scheduledExecutor).setRemoveOnCancelPolicy(removeOnCancelPolicy);
 		}
+		else if (removeOnCancelPolicy && this.scheduledExecutor != null) {
+			logger.info("Could not apply remove-on-cancel policy - not a Java 7+ ScheduledThreadPoolExecutor");
+		}
 	}
 
 	/**
 	 * Set a custom {@link ErrorHandler} strategy.
 	 */
 	public void setErrorHandler(ErrorHandler errorHandler) {
-		Assert.notNull(errorHandler, "'errorHandler' must not be null");
 		this.errorHandler = errorHandler;
 	}
 
+
 	@UsesJava7
 	@Override
 	protected ExecutorService initializeExecutor(
 			ThreadFactory threadFactory, RejectedExecutionHandler rejectedExecutionHandler) {
 
 		this.scheduledExecutor = createExecutor(this.poolSize, threadFactory, rejectedExecutionHandler);
 
-		if (this.scheduledExecutor instanceof ScheduledThreadPoolExecutor && this.removeOnCancelPolicy != null) {
-			((ScheduledThreadPoolExecutor) this.scheduledExecutor).setRemoveOnCancelPolicy(this.removeOnCancelPolicy);
+		if (this.removeOnCancelPolicy) {
+			if (setRemoveOnCancelPolicyAvailable && this.scheduledExecutor instanceof ScheduledThreadPoolExecutor) {
+				((ScheduledThreadPoolExecutor) this.scheduledExecutor).setRemoveOnCancelPolicy(true);
+			}
+			else {
+				logger.info("Could not apply remove-on-cancel policy - not a Java 7+ ScheduledThreadPoolExecutor");
+			}
 		}
 
 		return this.scheduledExecutor;
@@ -175,8 +189,8 @@ public int getPoolSize() {
 	@UsesJava7
 	public boolean isRemoveOnCancelPolicy() {
 		if (this.scheduledExecutor == null) {
-			// Not initialized yet: return false (the default of the executor)
-			return false;
+			// Not initialized yet: return our setting for the time being.
+			return (setRemoveOnCancelPolicyAvailable && this.removeOnCancelPolicy);
 		}
 		return getScheduledThreadPoolExecutor().getRemoveOnCancelPolicy();
 	}