sviolet.thistle.model.queue.AsyncWaiter Maven / Gradle / Ivy
/*
* Copyright (C) 2015-2017 S.Violet
*
* 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.
*
* Project GitHub: https://github.com/shepherdviolet/thistle
* Email: [email protected]
*/
package sviolet.thistle.model.queue;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.ReentrantLock;
import sviolet.thistle.entity.Destroyable;
/**
* 挂起当前线程等待异步线程的结果
*
* @author S.Violet
*/
public class AsyncWaiter implements Destroyable {
/**
* 超时时间ms
*/
private long timeout = 0;
private Result result;
private T value;
private Exception exception;
private final ReentrantLock lock = new ReentrantLock();
private final Condition condition = lock.newCondition();
/**
* 无限等待
*/
public AsyncWaiter() {
this(0);
}
/**
* @param timeout 超时时间(ms), 该参数<=0时无限等待
*/
public AsyncWaiter(long timeout) {
this.timeout = timeout;
}
/**
* [异步线程]回调传回结果
*
* @param value 结果对象
*/
public void callback(T value){
lock.lock();
try{
//can only be called once
if (result != null) {
//destroy data
if (value instanceof Destroyable){
((Destroyable) value).onDestroy();
}
return;
}
this.value = value;
this.result = Result.SUCCESS;
condition.signalAll();
}finally {
lock.unlock();
}
}
/**
* [异步线程]回调传回异常
*
* @param e 异常
*/
public void callback(Exception e){
lock.lock();
try{
//can only be called once
if (result != null) {
return;
}
this.exception = e;
this.result = Result.ERROR;
condition.signalAll();
}finally {
lock.unlock();
}
}
/**
* [原线程]获得结果对象
*/
public T getValue(){
return value;
}
/**
* [原线程]获得异常
*/
public Exception getException(){
if (exception == null){
return new Exception("empty exception from async task");
}
return exception;
}
/**
* [原线程]挂起当前线程等待异步线程的结果
* @return 结果类型
*/
public Result waitForResult(){
final long startMillis = System.currentTimeMillis();
try{
lock.lock();
if (timeout > 0) {
while (result == null) {
final long remainTimeout = timeout - (System.currentTimeMillis() - startMillis);
if (remainTimeout <= 0) {
result = Result.TIMEOUT;
break;
}
try {
if (!condition.await(remainTimeout, TimeUnit.MILLISECONDS)) {
result = Result.TIMEOUT;
break;
}
} catch (InterruptedException e) {
result = Result.ERROR;
exception = e;
break;
}
}
} else {
while (result == null){
try {
condition.await();
} catch (InterruptedException e) {
result = Result.ERROR;
exception = e;
break;
}
}
}
return result;
} finally {
lock.unlock();
}
}
@Override
public void onDestroy() {
if (this.value instanceof Destroyable) {
((Destroyable) this.value).onDestroy();
}
this.value = null;
}
public enum Result{
/**
* SUCCESS
*/
SUCCESS,
/**
* TIMEOUT
*/
TIMEOUT,
/**
* ERROR
*/
ERROR
}
}