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Apache CXF Core
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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.
 */

package org.apache.cxf.endpoint;

import java.util.Map;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;

import org.apache.cxf.message.Message;

/**
 * Asynchronous callback object for calls to {@link Client#invoke(ClientCallback, String, Object...)}
 * and related functions.
 *
 * The default behavior of this expects the following pattern:
 * 
 * ClientCallback cb = new ClientCallback();<>
 * 
client.invoke(cb, "someMethod", ....);
 * cb.wait();
 * // CXF calls notify on the callback object when the operation is complete.
 * 
 */
public class ClientCallback implements Future {

    protected Map context;
    protected Object[] result;
    protected Throwable exception;
    protected volatile boolean done;
    protected boolean cancelled;
    protected boolean started;

    public ClientCallback() {
    }

    /**
     * Called when a message is first received prior to any actions
     * being applied to the message.   The InterceptorChain is setup so
     * modifications to that can be done.
     */
    public void start(Message msg) {
        started = true;
    }

    /**
     * If the processing of the incoming message proceeds normally, this
     * method is called with the response context values and the resulting objects.
     *
     * The default behavior just stores the objects and calls notifyAll to wake
     * up threads waiting for the response.
     *
     * @param ctx
     * @param res
     */
    public void handleResponse(Map ctx, Object[] res) {
        context = ctx;
        result = res;
        done = true;
        synchronized (this) {
            notifyAll();
        }
    }

    /**
     * If processing of the incoming message results in an exception, this
     * method is called with the resulting exception.
     *
     * The default behavior just stores the objects and calls notifyAll to wake
     * up threads waiting for the response.
     *
     * @param ctx
     * @param ex
     */
    public void handleException(Map ctx, Throwable ex) {
        context = ctx;
        exception = ex;
        done = true;
        synchronized (this) {
            notifyAll();
        }
    }


    public boolean cancel(boolean mayInterruptIfRunning) {
        if (!started) {
            cancelled = true;
            synchronized (this) {
                notifyAll();
            }
            return true;
        }
        return false;
    }

    /**
     * return the map of items returned from an operation.
     * @return the response context
     * @throws InterruptedException if the operation was cancelled.
     * @throws ExecutionException if the operation resulted in a fault.
     */
    public Map getResponseContext() throws InterruptedException, ExecutionException {
        synchronized (this) {
            if (!done) {
                wait();
            }
        }
        if (cancelled) {
            throw new InterruptedException("Operation Cancelled");
        }
        if (exception != null) {
            throw new ExecutionException(exception);
        }
        return context;
    }

    /**
     * {@inheritDoc}
     */
    public Object[] get() throws InterruptedException, ExecutionException {
        synchronized (this) {
            if (!done) {
                wait();
            }
        }
        if (cancelled) {
            throw new InterruptedException("Operation Cancelled");
        }
        if (exception != null) {
            throw new ExecutionException(exception);
        }
        return result;
    }

    /**
     * {@inheritDoc}
     */
    public Object[] get(long timeout, TimeUnit unit)
        throws InterruptedException, ExecutionException, TimeoutException {
        synchronized (this) {
            if (!done) {
                unit.timedWait(this, timeout);
            }
        }
        if (cancelled) {
            throw new InterruptedException("Operation Cancelled");
        }
        if (!done) {
            throw new TimeoutException("Timeout Exceeded");
        }
        if (exception != null) {
            throw new ExecutionException(exception);
        }
        return result;
    }

    public boolean isCancelled() {
        return cancelled;
    }

    public boolean isDone() {
        return done;
    }

    /*
     * If the operation completes with a fault, the resulting exception object ends up here.
     */
    public Throwable getException() {
        return exception;
    }

}