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/*
 * Copyright 2002-2014 the original author or 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 com.foxinmy.weixin4j.util;

import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;
import java.util.concurrent.FutureTask;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import java.util.concurrent.atomic.AtomicReference;

/**
 * A {@link org.springframework.util.concurrent.ListenableFuture
 * ListenableFuture} whose value can be set via {@link #set(Object)} or
 * {@link #setException(Throwable)}. It may also be cancelled.
 *
 * 

* Inspired by {@code com.google.common.util.concurrent.SettableFuture}. * * @author Mattias Severson * @author Rossen Stoyanchev * @since 4.1 */ public class SettableFuture implements Future { private final SettableTask settableTask; private final FutureTask futureTask; public SettableFuture() { this.settableTask = new SettableTask(); this.futureTask = new FutureTask(this.settableTask); } /** * Set the value of this future. This method will return {@code true} if the * value was set successfully, or {@code false} if the future has already * been set or cancelled. * * @param value * the value that will be set. * @return {@code true} if the value was successfully set, else * {@code false}. */ public boolean set(T value) { boolean success = this.settableTask.setValue(value); if (success) { this.futureTask.run(); } return success; } /** * Set the exception of this future. This method will return {@code true} if * the exception was set successfully, or {@code false} if the future has * already been set or cancelled. * * @param exception * the value that will be set. * @return {@code true} if the exception was successfully set, else * {@code false}. */ public boolean setException(Throwable exception) { boolean success = this.settableTask.setException(exception); if (success) { this.futureTask.run(); } return success; } @Override public boolean cancel(boolean mayInterruptIfRunning) { this.settableTask.setCancelled(); boolean cancelled = this.futureTask.cancel(mayInterruptIfRunning); if (cancelled && mayInterruptIfRunning) { interruptTask(); } return cancelled; } @Override public boolean isCancelled() { return this.futureTask.isCancelled(); } @Override public boolean isDone() { return this.futureTask.isDone(); } /** * Retrieve the value. *

* Will return the value if it has been set via {@link #set(Object)}, throw * an {@link java.util.concurrent.ExecutionException} if it has been set via * {@link #setException(Throwable)} or throw a * {@link java.util.concurrent.CancellationException} if it has been * cancelled. * * @return The value associated with this future. */ @Override public T get() throws InterruptedException, ExecutionException { return this.futureTask.get(); } /** * Retrieve the value. *

* Will return the value if it has been set via {@link #set(Object)}, throw * an {@link java.util.concurrent.ExecutionException} if it has been set via * {@link #setException(Throwable)} or throw a * {@link java.util.concurrent.CancellationException} if it has been * cancelled. * * @param timeout * the maximum time to wait. * @param unit * the time unit of the timeout argument. * @return The value associated with this future. */ @Override public T get(long timeout, TimeUnit unit) throws InterruptedException, ExecutionException, TimeoutException { return this.futureTask.get(timeout, unit); } /** * Subclasses can override this method to implement interruption of the * future's computation. The method is invoked automatically by a successful * call to {@link #cancel(boolean) cancel(true)}. *

* The default implementation does nothing. */ protected void interruptTask() { } private static class SettableTask implements Callable { private static final String NO_VALUE = SettableFuture.class .getName() + ".NO_VALUE"; private final AtomicReference value = new AtomicReference( NO_VALUE); private volatile boolean cancelled = false; public boolean setValue(T value) { if (this.cancelled) { return false; } return this.value.compareAndSet(NO_VALUE, value); } public boolean setException(Throwable exception) { if (this.cancelled) { return false; } return this.value.compareAndSet(NO_VALUE, exception); } public void setCancelled() { this.cancelled = true; } @SuppressWarnings("unchecked") @Override public T call() throws Exception { if (value.get() instanceof Exception) { throw (Exception) value.get(); } return (T) value.get(); } } }