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Tomcat example source code file (RpcChannel.java)

This example Tomcat source code file (RpcChannel.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 - Tomcat tags/keywords

channel, io, majority_reply, member, no_reply, response, response, rpccallback, rpcchannel, rpccollector, rpccollector, rpccollectorkey, rpccollectorkey, rpcmessage, rpcmessage, util

The Tomcat RpcChannel.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.catalina.tribes.group;

import java.io.Serializable;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;

import org.apache.catalina.tribes.Channel;
import org.apache.catalina.tribes.ChannelException;
import org.apache.catalina.tribes.ChannelListener;
import org.apache.catalina.tribes.Member;
import org.apache.catalina.tribes.util.UUIDGenerator;

/**
 * A channel to handle RPC messaging
 * @author Filip Hanik
 */
public class RpcChannel implements ChannelListener{
    protected static org.apache.juli.logging.Log log = org.apache.juli.logging.LogFactory.getLog(RpcChannel.class);
    
    public static final int FIRST_REPLY = 1;
    public static final int MAJORITY_REPLY = 2;
    public static final int ALL_REPLY = 3;
    public static final int NO_REPLY = 4;
    
    private Channel channel;
    private RpcCallback callback;
    private byte[] rpcId;
    
    private HashMap responseMap = new HashMap();

    /**
     * Create an RPC channel. You can have several RPC channels attached to a group
     * all separated out by the uniqueness
     * @param rpcId - the unique Id for this RPC group
     * @param channel Channel
     * @param callback RpcCallback
     */
    public RpcChannel(byte[] rpcId, Channel channel, RpcCallback callback) {
        this.channel = channel;
        this.callback = callback;
        this.rpcId = rpcId;
        channel.addChannelListener(this);
    }
    
    
    /**
     * Send a message and wait for the response.
     * @param destination Member[] - the destination for the message, and the members you request a reply from
     * @param message Serializable - the message you are sending out
     * @param options int - FIRST_REPLY, MAJORITY_REPLY or ALL_REPLY
     * @param timeout long - timeout in milliseconds, if no reply is received within this time null is returned
     * @return Response[] - an array of response objects.
     * @throws ChannelException
     */
    public Response[] send(Member[] destination, 
                           Serializable message,
                           int rpcOptions, 
                           int channelOptions,
                           long timeout) throws ChannelException {
        
        if ( destination==null || destination.length == 0 ) return new Response[0];
        
        //avoid dead lock
        channelOptions = channelOptions & ~Channel.SEND_OPTIONS_SYNCHRONIZED_ACK;
        
        RpcCollectorKey key = new RpcCollectorKey(UUIDGenerator.randomUUID(false));
        RpcCollector collector = new RpcCollector(key,rpcOptions,destination.length,timeout);
        try {
            synchronized (collector) {
                if ( rpcOptions != NO_REPLY ) responseMap.put(key, collector);
                RpcMessage rmsg = new RpcMessage(rpcId, key.id, message);
                channel.send(destination, rmsg, channelOptions);
                if ( rpcOptions != NO_REPLY ) collector.wait(timeout);
            }
        } catch ( InterruptedException ix ) {
            Thread.currentThread().interrupted();
            //throw new ChannelException(ix);
        }finally {
            responseMap.remove(key);
        }
        return collector.getResponses();
    }
    
    public void messageReceived(Serializable msg, Member sender) {
        RpcMessage rmsg = (RpcMessage)msg;
        RpcCollectorKey key = new RpcCollectorKey(rmsg.uuid);
        if ( rmsg.reply ) {
            RpcCollector collector = (RpcCollector)responseMap.get(key);
            if (collector == null) {
                callback.leftOver(rmsg.message, sender);
            } else {
                synchronized (collector) {
                    //make sure it hasn't been removed
                    if ( responseMap.containsKey(key) ) {
                        if ( (rmsg instanceof RpcMessage.NoRpcChannelReply) ) 
                            collector.destcnt--;
                        else 
                            collector.addResponse(rmsg.message, sender);
                        if (collector.isComplete()) collector.notifyAll();
                    } else {
                        if (! (rmsg instanceof RpcMessage.NoRpcChannelReply) ) 
                            callback.leftOver(rmsg.message, sender);
                    }
                }//synchronized
            }//end if
        } else{
            Serializable reply = callback.replyRequest(rmsg.message,sender);
            rmsg.reply = true;
            rmsg.message = reply;
            try {
                channel.send(new Member[] {sender}, rmsg,0);
            }catch ( Exception x )  {
                log.error("Unable to send back reply in RpcChannel.",x);
            }
        }//end if
    }
    
    public void breakdown() {
        channel.removeChannelListener(this);
    }
    
    public void finalize() {
        breakdown();
    }
    
    public boolean accept(Serializable msg, Member sender) {
        if ( msg instanceof RpcMessage ) {
            RpcMessage rmsg = (RpcMessage)msg;
            return Arrays.equals(rmsg.rpcId,rpcId);
        }else return false;
    }
    
    public Channel getChannel() {
        return channel;
    }

    public RpcCallback getCallback() {
        return callback;
    }

    public byte[] getRpcId() {
        return rpcId;
    }

    public void setChannel(Channel channel) {
        this.channel = channel;
    }

    public void setCallback(RpcCallback callback) {
        this.callback = callback;
    }

    public void setRpcId(byte[] rpcId) {
        this.rpcId = rpcId;
    }
    


    /**
     * 
     * Class that holds all response.
     * @author not attributable
     * @version 1.0
     */
    public static class RpcCollector {
        public ArrayList responses = new ArrayList(); 
        public RpcCollectorKey key;
        public int options;
        public int destcnt;
        public long timeout;
        
        public RpcCollector(RpcCollectorKey key, int options, int destcnt, long timeout) {
            this.key = key;
            this.options = options;
            this.destcnt = destcnt;
            this.timeout = timeout;
        }
        
        public void addResponse(Serializable message, Member sender){
            Response resp = new Response(sender,message);
            responses.add(resp);
        }
        
        public boolean isComplete() {
            if ( destcnt <= 0 ) return true;
            switch (options) {
                case ALL_REPLY:
                    return destcnt == responses.size();
                case MAJORITY_REPLY:
                {
                    float perc = ((float)responses.size()) / ((float)destcnt);
                    return perc >= 0.50f;
                }
                case FIRST_REPLY:
                    return responses.size()>0;
                default:
                    return false;
            }
        }
        
        public int hashCode() {
            return key.hashCode();
        }
        
        public boolean equals(Object o) {
            if ( o instanceof RpcCollector ) {
                RpcCollector r = (RpcCollector)o;
                return r.key.equals(this.key);
            } else return false;
        }
        
        public Response[] getResponses() {
            return (Response[])responses.toArray(new Response[responses.size()]);
        }
    }
    
    public static class RpcCollectorKey {
        byte[] id;
        public RpcCollectorKey(byte[] id) {
            this.id = id;
        }
        
        public int hashCode() {
            return id[0]+id[1]+id[2]+id[3];
        }

        public boolean equals(Object o) {
            if ( o instanceof RpcCollectorKey ) {
                RpcCollectorKey r = (RpcCollectorKey)o;
                return Arrays.equals(id,r.id);
            } else return false;
        }
        
    }
    
    protected static String bToS(byte[] data) {
        StringBuffer buf = new StringBuffer(4*16);
        buf.append("{");
        for (int i=0; data!=null && i<data.length; i++ ) buf.append(String.valueOf(data[i])).append(" ");
        buf.append("}");
        return buf.toString();
    }


}

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