/* * Copyright 2007 Sun Microsystems, Inc. All Rights Reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Sun designates this * particular file as subject to the "Classpath" exception as provided * by Sun in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, * CA 95054 USA or visit www.sun.com if you need additional information or * have any questions. */ package com.sun.jmx.event; import com.sun.jmx.remote.util.ClassLogger; import java.util.concurrent.Executor; import java.util.concurrent.RejectedExecutionException; /** *
A task that is repeatedly run by an Executor. The task will be * repeated as long as the {@link #isSuspended()} method returns true. Once * that method returns false, the task is no longer executed until someone * calls {@link #resume()}.
* @author sjiang */ public abstract class RepeatedSingletonJob implements Runnable { public RepeatedSingletonJob(Executor executor) { if (executor == null) { throw new NullPointerException("Null executor!"); } this.executor = executor; } public boolean isWorking() { return working; } public void resume() { synchronized(this) { if (!working) { if (logger.traceOn()) { logger.trace("resume", ""); } working = true; execute(); } } } public abstract void task(); public abstract boolean isSuspended(); public void run() { if (logger.traceOn()) { logger.trace("run", "execute the task"); } try { task(); } catch (Exception e) { // A correct task() implementation should not throw exceptions. // It may cause isSuspended() to start returning true, though. logger.trace("run", "failed to execute the task", e); } synchronized(this) { if (!isSuspended()) { execute(); } else { if (logger.traceOn()) { logger.trace("run", "suspend the task"); } working = false; } } } private void execute() { try { executor.execute(this); } catch (RejectedExecutionException e) { logger.warning( "setEventReceiver", "Executor threw exception", e); throw new RejectedExecutionException( "Executor.execute threw exception -" + "should not be possible", e); // User-supplied Executor should not be configured in a way that // might cause this exception, for example if it is shared between // several client objects and doesn't have capacity for one job // from each one. CR 6732037 will add text to the spec explaining // the problem. The rethrown exception will propagate either out // of resume() to user code, or out of run() to the Executor // (which will probably ignore it). } } private boolean working = false; private final Executor executor; private static final ClassLogger logger = new ClassLogger("javax.management.event", "RepeatedSingletonJob"); }