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ActiveMQ example source code file (CommandDatagramChannel.java)

This example ActiveMQ source code file (CommandDatagramChannel.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

bytearrayoutputstream, bytebuffer, bytebuffer, bytebufferpool, command, commanddatagramchannel, datagramchannel, datainputstream, io, ioexception, ioexception, net, network, nio, object, object, socketaddress, socketaddress

The ActiveMQ CommandDatagramChannel.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.udp;

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.net.SocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.DatagramChannel;

import org.apache.activemq.command.Command;
import org.apache.activemq.command.Endpoint;
import org.apache.activemq.command.LastPartialCommand;
import org.apache.activemq.command.PartialCommand;
import org.apache.activemq.openwire.BooleanStream;
import org.apache.activemq.openwire.OpenWireFormat;
import org.apache.activemq.transport.reliable.ReplayBuffer;
import org.apache.activemq.util.ByteArrayInputStream;
import org.apache.activemq.util.ByteArrayOutputStream;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * A strategy for reading datagrams and de-fragmenting them together.
 * 
 * 
 */
public class CommandDatagramChannel extends CommandChannelSupport {

    private static final Logger LOG = LoggerFactory.getLogger(CommandDatagramChannel.class);

    private DatagramChannel channel;
    private ByteBufferPool bufferPool;

    // reading
    private Object readLock = new Object();
    private ByteBuffer readBuffer;

    // writing
    private Object writeLock = new Object();
    private int defaultMarshalBufferSize = 64 * 1024;
    private volatile int receiveCounter;

    public CommandDatagramChannel(UdpTransport transport, OpenWireFormat wireFormat, int datagramSize, SocketAddress targetAddress, DatagramHeaderMarshaller headerMarshaller,
                                  DatagramChannel channel, ByteBufferPool bufferPool) {
        super(transport, wireFormat, datagramSize, targetAddress, headerMarshaller);
        this.channel = channel;
        this.bufferPool = bufferPool;
    }

    public void start() throws Exception {
        bufferPool.setDefaultSize(datagramSize);
        bufferPool.start();
        readBuffer = bufferPool.borrowBuffer();
    }

    public void stop() throws Exception {
        bufferPool.stop();
    }

    public Command read() throws IOException {
        Command answer = null;
        Endpoint from = null;
        synchronized (readLock) {
            while (true) {
                readBuffer.clear();
                SocketAddress address = channel.receive(readBuffer);

                readBuffer.flip();

                if (readBuffer.limit() == 0) {
                    continue;
                }
                
                receiveCounter++;
                from = headerMarshaller.createEndpoint(readBuffer, address);

                int remaining = readBuffer.remaining();
                byte[] data = new byte[remaining];
                readBuffer.get(data);

                // TODO could use a DataInput implementation that talks direct
                // to
                // the ByteBuffer to avoid object allocation and unnecessary
                // buffering?
                DataInputStream dataIn = new DataInputStream(new ByteArrayInputStream(data));
                answer = (Command)wireFormat.unmarshal(dataIn);
                break;
            }
        }
        if (answer != null) {
            answer.setFrom(from);

            if (LOG.isDebugEnabled()) {
                LOG.debug("Channel: " + name + " received from: " + from + " about to process: " + answer);
            }
        }
        return answer;
    }

    public void write(Command command, SocketAddress address) throws IOException {
        synchronized (writeLock) {

            ByteArrayOutputStream largeBuffer = new ByteArrayOutputStream(defaultMarshalBufferSize);
            wireFormat.marshal(command, new DataOutputStream(largeBuffer));
            byte[] data = largeBuffer.toByteArray();
            int size = data.length;

            ByteBuffer writeBuffer = bufferPool.borrowBuffer();
            writeBuffer.clear();
            headerMarshaller.writeHeader(command, writeBuffer);

            if (size > writeBuffer.remaining()) {
                // lets split the command up into chunks
                int offset = 0;
                boolean lastFragment = false;
                int length = data.length;
                for (int fragment = 0; !lastFragment; fragment++) {
                    // write the header
                    if (fragment > 0) {
                        writeBuffer = bufferPool.borrowBuffer();
                        writeBuffer.clear();
                        headerMarshaller.writeHeader(command, writeBuffer);
                    }

                    int chunkSize = writeBuffer.remaining();

                    // we need to remove the amount of overhead to write the
                    // partial command

                    // lets write the flags in there
                    BooleanStream bs = null;
                    if (wireFormat.isTightEncodingEnabled()) {
                        bs = new BooleanStream();
                        bs.writeBoolean(true); // the partial data byte[] is
                        // never null
                    }

                    // lets remove the header of the partial command
                    // which is the byte for the type and an int for the size of
                    // the byte[]

                    // data type + the command ID + size of the partial data
                    chunkSize -= 1 + 4 + 4;

                    // the boolean flags
                    if (bs != null) {
                        chunkSize -= bs.marshalledSize();
                    } else {
                        chunkSize -= 1;
                    }

                    if (!wireFormat.isSizePrefixDisabled()) {
                        // lets write the size of the command buffer
                        writeBuffer.putInt(chunkSize);
                        chunkSize -= 4;
                    }

                    lastFragment = offset + chunkSize >= length;
                    if (chunkSize + offset > length) {
                        chunkSize = length - offset;
                    }

                    if (lastFragment) {
                        writeBuffer.put(LastPartialCommand.DATA_STRUCTURE_TYPE);
                    } else {
                        writeBuffer.put(PartialCommand.DATA_STRUCTURE_TYPE);
                    }

                    if (bs != null) {
                        bs.marshal(writeBuffer);
                    }

                    int commandId = command.getCommandId();
                    if (fragment > 0) {
                        commandId = sequenceGenerator.getNextSequenceId();
                    }
                    writeBuffer.putInt(commandId);
                    if (bs == null) {
                        writeBuffer.put((byte)1);
                    }

                    // size of byte array
                    writeBuffer.putInt(chunkSize);

                    // now the data
                    writeBuffer.put(data, offset, chunkSize);

                    offset += chunkSize;
                    sendWriteBuffer(commandId, address, writeBuffer, false);
                }
            } else {
                writeBuffer.put(data);
                sendWriteBuffer(command.getCommandId(), address, writeBuffer, false);
            }
        }
    }

    // Properties
    // -------------------------------------------------------------------------

    public ByteBufferPool getBufferPool() {
        return bufferPool;
    }

    /**
     * Sets the implementation of the byte buffer pool to use
     */
    public void setBufferPool(ByteBufferPool bufferPool) {
        this.bufferPool = bufferPool;
    }

    // Implementation methods
    // -------------------------------------------------------------------------
    protected void sendWriteBuffer(int commandId, SocketAddress address, ByteBuffer writeBuffer, boolean redelivery) throws IOException {
        // lets put the datagram into the replay buffer first to prevent timing
        // issues
        ReplayBuffer bufferCache = getReplayBuffer();
        if (bufferCache != null && !redelivery) {
            bufferCache.addBuffer(commandId, writeBuffer);
        }

        writeBuffer.flip();

        if (LOG.isDebugEnabled()) {
            String text = redelivery ? "REDELIVERING" : "sending";
            LOG.debug("Channel: " + name + " " + text + " datagram: " + commandId + " to: " + address);
        }
        channel.send(writeBuffer, address);
    }

    public void sendBuffer(int commandId, Object buffer) throws IOException {
        if (buffer != null) {
            ByteBuffer writeBuffer = (ByteBuffer)buffer;
            sendWriteBuffer(commandId, getReplayAddress(), writeBuffer, true);
        } else {
            if (LOG.isWarnEnabled()) {
                LOG.warn("Request for buffer: " + commandId + " is no longer present");
            }
        }
    }

    public int getReceiveCounter() {
        return receiveCounter;
    }

}

Other ActiveMQ examples (source code examples)

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



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