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The Netty project is an effort to provide an asynchronous event-driven network application framework and tools for rapid development of maintainable high performance and high scalability protocol servers and clients. In other words, Netty is a NIO client server framework which enables quick and easy development of network applications such as protocol servers and clients. It greatly simplifies and streamlines network programming such as TCP and UDP socket server.

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/*
 * JBoss, Home of Professional Open Source
 *
 * Copyright 2008, Red Hat Middleware LLC, and individual contributors
 * by the @author tags. See the COPYRIGHT.txt in the distribution for a
 * full listing of individual contributors.
 *
 * This is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This software is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
 */
package org.jboss.netty.handler.codec.serialization;

import static org.jboss.netty.buffer.ChannelBuffers.*;

import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;

import org.jboss.netty.buffer.ChannelBuffer;
import org.jboss.netty.buffer.ChannelBufferOutputStream;
import org.jboss.netty.channel.Channel;
import org.jboss.netty.channel.ChannelHandlerContext;
import org.jboss.netty.channel.ChannelPipelineCoverage;
import org.jboss.netty.handler.codec.oneone.OneToOneEncoder;

/**
 * An encoder which serializes a Java object into a {@link ChannelBuffer}.
 * 
 * Please note that the serialized form this encoder produces is not
 * compatible with the standard {@link ObjectInputStream}.  Please use
 * {@link ObjectDecoder} or {@link ObjectDecoderInputStream} to ensure the
 * interoperability with this encoder.
 *
 * @author The Netty Project ([email protected])
 * @author Trustin Lee ([email protected])
 *
 * @version $Rev:231 $, $Date:2008-06-12 16:44:50 +0900 (목, 12 6월 2008) $
 *
 * @apiviz.landmark
 */
@ChannelPipelineCoverage("all")
public class ObjectEncoder extends OneToOneEncoder {
    private static final byte[] LENGTH_PLACEHOLDER = new byte[4];

    private final int estimatedLength;

    /**
     * Creates a new encoder with the estimated length of 512 bytes.
     */
    public ObjectEncoder() {
        this(512);
    }

    /**
     * Creates a new encoder.
     *
     * @param estimatedLength
     *        the estimated byte length of the serialized form of an object.
     *        If the length of the serialized form exceeds this value, the
     *        internal buffer will be expanded automatically at the cost of
     *        memory bandwidth.  If this value is too big, it will also waste
     *        memory bandwidth.  To avoid unnecessary memory copy or allocation
     *        cost, please specify the properly estimated value.
     */
    public ObjectEncoder(int estimatedLength) {
        if (estimatedLength < 0) {
            throw new IllegalArgumentException(
                    "estimatedLength: " + estimatedLength);
        }
        this.estimatedLength = estimatedLength;
    }

    @Override
    protected Object encode(ChannelHandlerContext ctx, Channel channel, Object msg) throws Exception {
        ChannelBufferOutputStream bout =
            new ChannelBufferOutputStream(dynamicBuffer(
                    estimatedLength, ctx.getChannel().getConfig().getBufferFactory()));
        bout.write(LENGTH_PLACEHOLDER);
        ObjectOutputStream oout = new CompactObjectOutputStream(bout);
        oout.writeObject(msg);
        oout.flush();
        oout.close();

        ChannelBuffer encoded = bout.buffer();
        encoded.setInt(0, encoded.writerIndex() - 4);
        return encoded;
    }
}