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/*
* Copyright 2007-2008 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;
/**
* <p>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()}.</p>
* @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(
"execute",
"Executor threw exception (" + this.getClass().getName() + ")",
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");
}
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