org.joyqueue.toolkit.concurrent.EventFuture Maven / Gradle / Ivy
/**
* Copyright 2019 The JoyQueue Authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.joyqueue.toolkit.concurrent;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
/**
* @author liyue25
* Date: 2018/11/9
*/
public class EventFuture implements Future,EventListener{
private R result = null;
private final Lock lock = new ReentrantLock();
private final Condition condition = lock.newCondition();
private volatile boolean done = false;
/**
* 事件处理，不要抛出异常
*
* @param event 事件
*/
@Override
public void onEvent(R event) {
lock.lock();
try {
if(!done) {
result = event;
done = true;
condition.signal();
}
} finally {
lock.unlock();
}
}
/**
* Attempts to cancel execution of this task. This attempt will
* fail if the task has already completed, has already been cancelled,
* or could not be cancelled for some other reason. If successful,
* and this task has not started when {@code cancel} is called,
* this task should never run. If the task has already started,
* then the {@code mayInterruptIfRunning} parameter determines
* whether the thread executing this task should be interrupted in
* an attempt to stop the task.
*
* After this method returns, subsequent calls to {@link #isDone} will
* always return {@code true}. Subsequent calls to {@link #isCancelled}
* will always return {@code true} if this method returned {@code true}.
*
* @param mayInterruptIfRunning {@code true} if the thread executing this
* task should be interrupted; otherwise, in-progress tasks are allowed
* to complete
* @return {@code false} if the task could not be cancelled,
* typically because it has already completed normally;
* {@code true} otherwise
*/
@Override
public boolean cancel(boolean mayInterruptIfRunning) {
// not supported
return false;
}
/**
* Returns {@code true} if this task was cancelled before it completed
* normally.
*
* @return {@code true} if this task was cancelled before it completed
*/
@Override
public boolean isCancelled() {
return false;
}
/**
* Returns {@code true} if this task completed.
*
* Completion may be due to normal termination, an exception, or
* cancellation -- in all of these cases, this method will return
* {@code true}.
*
* @return {@code true} if this task completed
*/
@Override
public boolean isDone() {
return done;
}
/**
* Waits if necessary for the computation to complete, and then
* retrieves its result.
*
* @return the computed result
* @throws java.util.concurrent.CancellationException if the computation was cancelled
* @throws InterruptedException if the current thread was interrupted
* while waiting
*/
@Override
public R get() throws InterruptedException {
lock.lock();
try {
if(!done) {
condition.await();
}
}finally {
lock.unlock();
}
return result;
}
/**
* Waits if necessary for at most the given time for the computation
* to complete, and then retrieves its result, if available.
*
* @param timeout the maximum time to wait
* @param unit the time unit of the timeout argument
* @return the computed result
* @throws InterruptedException if the current thread was interrupted
* while waiting
*/
@Override
public R get(long timeout, TimeUnit unit) throws InterruptedException, TimeoutException {
lock.lock();
try {
if(!done) {
if (!condition.await(timeout, unit)) {
throw new TimeoutException();
}
}
}finally {
lock.unlock();
}
return result;
}
}