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ActiveMQ example source code file (ResponseCorrelator.java)

This example ActiveMQ source code file (ResponseCorrelator.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - ActiveMQ tags/keywords

command, command, exceptionresponse, futureresponse, futureresponse, intsequencegenerator, io, ioexception, ioexception, logger, object, object, override, response, responsecorrelator, util

The ActiveMQ ResponseCorrelator.java source code

/**
 * 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.activemq.transport;

import java.io.IOException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

import org.apache.activemq.command.Command;
import org.apache.activemq.command.ExceptionResponse;
import org.apache.activemq.command.Response;
import org.apache.activemq.util.IntSequenceGenerator;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Adds the incrementing sequence number to commands along with performing the
 * corelation of responses to requests to create a blocking request-response
 * semantics.
 * 
 * 
 */
public class ResponseCorrelator extends TransportFilter {

    private static final Logger LOG = LoggerFactory.getLogger(ResponseCorrelator.class);
    private final Map<Integer, FutureResponse> requestMap = new HashMap();
    private IntSequenceGenerator sequenceGenerator;
    private final boolean debug = LOG.isDebugEnabled();
    private IOException error;

    public ResponseCorrelator(Transport next) {
        this(next, new IntSequenceGenerator());
    }

    public ResponseCorrelator(Transport next, IntSequenceGenerator sequenceGenerator) {
        super(next);
        this.sequenceGenerator = sequenceGenerator;
    }

    public void oneway(Object o) throws IOException {
        Command command = (Command)o;
        command.setCommandId(sequenceGenerator.getNextSequenceId());
        command.setResponseRequired(false);
        next.oneway(command);
    }

    public FutureResponse asyncRequest(Object o, ResponseCallback responseCallback) throws IOException {
        Command command = (Command) o;
        command.setCommandId(sequenceGenerator.getNextSequenceId());
        command.setResponseRequired(true);
        FutureResponse future = new FutureResponse(responseCallback);
        IOException priorError = null;
        synchronized (requestMap) {
            priorError = this.error;
            if (priorError == null) {
                requestMap.put(new Integer(command.getCommandId()), future);
            }
        }

        if (priorError != null) {
            future.set(new ExceptionResponse(priorError));
            throw priorError;
        }

        next.oneway(command);
        return future;
    }

    public Object request(Object command) throws IOException {
        FutureResponse response = asyncRequest(command, null);
        return response.getResult();
    }

    public Object request(Object command, int timeout) throws IOException {
        FutureResponse response = asyncRequest(command, null);
        return response.getResult(timeout);
    }

    public void onCommand(Object o) {
        Command command = null;
        if (o instanceof Command) {
            command = (Command)o;
        } else {
            throw new ClassCastException("Object cannot be converted to a Command,  Object: " + o);
        }
        if (command.isResponse()) {
            Response response = (Response)command;
            FutureResponse future = null;
            synchronized (requestMap) {
                future = requestMap.remove(Integer.valueOf(response.getCorrelationId()));
            }
            if (future != null) {
                future.set(response);
            } else {
                if (debug) {
                    LOG.debug("Received unexpected response: {" + command + "}for command id: " + response.getCorrelationId());
                }
            }
        } else {
            getTransportListener().onCommand(command);
        }
    }

    /**
     * If an async exception occurs, then assume no responses will arrive for
     * any of current requests. Lets let them know of the problem.
     */
    public void onException(IOException error) {
        dispose(error);
        super.onException(error);
    }
    
    @Override
    public void stop() throws Exception {
        dispose(new IOException("Stopped."));
        super.stop();
    }

    private void dispose(IOException error) {
        ArrayList<FutureResponse> requests=null; 
        synchronized(requestMap) {
            if( this.error==null) {
                this.error = error;
                requests = new ArrayList<FutureResponse>(requestMap.values());
                requestMap.clear();
            }
        }
        if( requests!=null ) {
            for (Iterator<FutureResponse> iter = requests.iterator(); iter.hasNext();) {
                FutureResponse fr = iter.next();
                fr.set(new ExceptionResponse(error));
            }
        }
    }

    public IntSequenceGenerator getSequenceGenerator() {
        return sequenceGenerator;
    }

    public String toString() {
        return next.toString();
    }
}

Other ActiveMQ examples (source code examples)

Here is a short list of links related to this ActiveMQ ResponseCorrelator.java source code file:

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