ActiveMQ example source code file (MessageEndpointProxy.java)

This example ActiveMQ source code file (MessageEndpointProxy.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

dead, dead, illegalstateexception, invalidmessageendpointexception, invoking, message, messageendpointstate, messageendpointstate, messagelistener, method, nosuchmethodexception, nosuchmethodexception, reflection, resourceexception, resourceexception

The ActiveMQ MessageEndpointProxy.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.ra;

import java.lang.reflect.Method;

import javax.jms.Message;
import javax.jms.MessageListener;
import javax.resource.ResourceException;
import javax.resource.spi.endpoint.MessageEndpoint;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * @author <a href="mailto:michael.gaffney@panacya.com">Michael Gaffney 
 */
public class MessageEndpointProxy implements MessageListener, MessageEndpoint {

    private static final MessageEndpointState ALIVE = new MessageEndpointAlive();
    private static final MessageEndpointState DEAD = new MessageEndpointDead();
    private static final Logger LOG = LoggerFactory.getLogger(MessageEndpointProxy.class);

    private static int proxyCount;
    private final int proxyID;

    private final MessageEndpoint endpoint;
    private final MessageListener messageListener;
    private MessageEndpointState state = ALIVE;

    public MessageEndpointProxy(MessageEndpoint endpoint) {
        if (!(endpoint instanceof MessageListener)) {
            throw new IllegalArgumentException("MessageEndpoint is not a MessageListener");
        }
        messageListener = (MessageListener)endpoint;
        proxyID = getID();
        this.endpoint = endpoint;
    }

    private static int getID() {
        return ++proxyCount;
    }

    public void beforeDelivery(Method method) throws NoSuchMethodException, ResourceException {
        LOG.trace("Invoking MessageEndpoint.beforeDelivery()");
        state.beforeDelivery(this, method);
    }

    public void onMessage(Message message) {
        LOG.trace("Invoking MessageEndpoint.onMethod()");
        state.onMessage(this, message);
    }

    public void afterDelivery() throws ResourceException {
        LOG.trace("Invoking MessageEndpoint.afterDelivery()");
        state.afterDelivery(this);
    }

    public void release() {
        LOG.trace("Invoking MessageEndpoint.release()");
        state.release(this);
    }

    public String toString() {
        return "MessageEndpointProxy{ " + "proxyID: " + proxyID + ", endpoint: " + endpoint + " }";
    }

    private abstract static class MessageEndpointState {

        public void beforeDelivery(MessageEndpointProxy proxy, Method method) throws NoSuchMethodException, ResourceException {
            throw new IllegalStateException();
        }

        public void onMessage(MessageEndpointProxy proxy, Message message) {
            throw new IllegalStateException();
        }

        public void afterDelivery(MessageEndpointProxy proxy) throws ResourceException {
            throw new IllegalStateException();
        }

        public void release(MessageEndpointProxy proxy) {
            throw new IllegalStateException();
        }

        protected final void transition(MessageEndpointProxy proxy, MessageEndpointState nextState) {
            proxy.state = nextState;
            nextState.enter(proxy);
        }

        protected void enter(MessageEndpointProxy proxy) {
        }
    }

    private static class MessageEndpointAlive extends MessageEndpointState {

        public void beforeDelivery(MessageEndpointProxy proxy, Method method) throws NoSuchMethodException, ResourceException {
            try {
                proxy.endpoint.beforeDelivery(method);
            } catch (NoSuchMethodException e) {
                transition(proxy, DEAD);
                throw e;
            } catch (ResourceException e) {
                transition(proxy, DEAD);
                throw e;
            }
        }

        public void onMessage(MessageEndpointProxy proxy, Message message) {
            proxy.messageListener.onMessage(message);
        }

        public void afterDelivery(MessageEndpointProxy proxy) throws ResourceException {
            try {
                proxy.endpoint.afterDelivery();
            } catch (ResourceException e) {
                transition(proxy, DEAD);
                throw e;
            }
        }

        public void release(MessageEndpointProxy proxy) {
            transition(proxy, DEAD);
        }
    }

    private static class MessageEndpointDead extends MessageEndpointState {

        protected void enter(MessageEndpointProxy proxy) {
            proxy.endpoint.release();
        }

        public void beforeDelivery(MessageEndpointProxy proxy, Method method) throws NoSuchMethodException, ResourceException {
            throw new InvalidMessageEndpointException();
        }

        public void onMessage(MessageEndpointProxy proxy, Message message) {
            throw new InvalidMessageEndpointException();
        }

        public void afterDelivery(MessageEndpointProxy proxy) throws ResourceException {
            throw new InvalidMessageEndpointException();
        }

        public void release(MessageEndpointProxy proxy) {
            throw new InvalidMessageEndpointException();
        }
    }
}