utils.concurrent.BasicFuture.java Source code

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Here is the source code for utils.concurrent.BasicFuture.java

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/*
 * ==================================================================== 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 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;

/**
 * Apache HttpClient 4.2 ?Future.
 */
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();
}