mq5.0-source.main.comm-util.src.main.java.com.sun.messaging.jmq.util.LockTable Maven / Gradle / Ivy
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/*
* @(#)LockTable.java 1.3 06/29/07
*/
package com.sun.messaging.jmq.util;
import java.util.*;
/**
* this is a generic class which allows you to wait for notification
* that an event has occurred even if the objects are different but
* equivalent (generate the same hashCode/isequals == true)
*/
public class LockTable
{
HashMap notifyTable = new HashMap();
/**
* Request notification when notifiy is called on the same or
* equivalent instance of an object. This method should be called
* before any notification could occur.
* @param object object to wait for notification on
* @throws IllegalAccessException indicates the system is already waiting
* on that object
*/
public void requestNotify(Object object) throws IllegalAccessException {
synchronized(notifyTable) {
if (notifyTable.containsKey(object))
throw new IllegalAccessException("Already waiting for " + object);
Object lock = new IDLock();
notifyTable.put(object, lock);
}
}
/**
* Cancel notification on an object. Cleans up any
* allocated resources. This call does NOT wake up
* any resources waiting for notification.
* @param object equivalent object to the one passed into
* requestNotify
*/
public void cancelNotify(Object object) {
synchronized(notifyTable) {
notifyTable.remove(object);
}
}
// we cant just sync on interest .. it could be a different
// object w/ the same contents
/**
* Wait for notification on an object.
*
* @param object equivalent object to the one passed into
* requestNotify
*/
public void wait(Object object) {
wait(object, 0 /* no timeout */);
}
/**
* Waits up to a timeout for notification on an object.
*
* @param timeout time (in milliseconds) to wait for the
* notification
* @param object equivalent object to the one passed into
* requestNotify
* @returns true if the notification was received, false
* if the system timed out.
*/
public boolean wait(Object object, long timeout) {
// OK first get the lock
IDLock lock = null;
synchronized (notifyTable) {
lock = (IDLock)notifyTable.get(object);
}
if (lock == null) return true; // done
synchronized(lock) {
if (lock.isValid()) {
try {
lock.wait(timeout);
} catch (Exception ex) {
ex.printStackTrace();
}
}
if (lock.isValid() ) {
// wait did not complete
return false;
}
synchronized(notifyTable) {
lock = (IDLock)notifyTable.remove(object);
}
return true;
}
}
/**
* Notify the system that the operation has completed.
*
* @param object equivalent object to the one passed into
* requestNotify
*/
public void notify(Object object) {
IDLock lock = null;
synchronized (notifyTable) {
lock = (IDLock)notifyTable.get(object);
}
if (lock == null) return;
synchronized(lock) {
lock.destroy();
lock.notify();
}
}
}
class IDLock {
boolean valid = true;
public IDLock() {
}
public void destroy() {
valid = false;
}
public boolean isValid() {
return valid;
}
}