/*
* ==================================================================== Licensed to the Apache Software Foundation (ASF)
* under one or more contributor license agreements. See the NOTICE file distributed with this work for additional
* information regarding copyright ownership. The ASF licenses this file to you 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.
* ====================================================================
*
* This software consists of voluntary contributions made by many individuals on behalf of the Apache Software
* Foundation. For more information on the Apache Software Foundation, please see <http://www.apache.org/>.
*
*/
package org.springside.modules.utils.concurrent;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import org.apache.commons.lang3.Validate;
/**
* 从Apache HttpClient 4.2 移植,一个Future实现类的基本框架.
*/
public abstract class BasicFuture<T> implements Future<T> {
private volatile boolean completed;
private volatile boolean cancelled;
private volatile T result;
private volatile Exception ex;
@Override
public boolean isCancelled() {
return this.cancelled;
}
@Override
public boolean isDone() {
return this.completed;
}
@Override
public synchronized T get() throws InterruptedException, ExecutionException {
while (!this.completed) {
wait();
}
return getResult();
}
@Override
public synchronized T get(final long timeout, final TimeUnit unit)
throws InterruptedException, ExecutionException, TimeoutException {
Validate.notNull(unit, "Time unit");
final long msecs = unit.toMillis(timeout);
final long startTime = (msecs <= 0) ? 0 : System.currentTimeMillis();
long waitTime = msecs;
if (this.completed) {
return getResult();
} else if (waitTime <= 0) {
throw new TimeoutException();
} else {
for (;;) {
wait(waitTime);
if (this.completed) {
return getResult();
} else {
waitTime = msecs - (System.currentTimeMillis() - startTime);
if (waitTime <= 0) {
throw new TimeoutException();
}
}
}
}
}
private T getResult() throws ExecutionException {
if (this.ex != null) {
throw new ExecutionException(this.ex);
}
return this.result;
}
public boolean completed(final T result) {
synchronized (this) {
if (this.completed) {
return false;
}
this.completed = true;
this.result = result;
notifyAll();
}
onCompleted(result);
return true;
}
public boolean failed(final Exception exception) {
synchronized (this) {
if (this.completed) {
return false;
}
this.completed = true;
this.ex = exception;
notifyAll();
}
onFailed(exception);
return true;
}
@Override
public boolean cancel(final boolean mayInterruptIfRunning) {
synchronized (this) {
if (this.completed) {
return false;
}
this.completed = true;
this.cancelled = true;
notifyAll();
}
onCancelled();
return true;
}
protected abstract void onCompleted(T result);
protected abstract void onFailed(Exception ex);
protected abstract void onCancelled();
}