Netty编解码技术和UDP实现

作为网络传输框架，免不了传输对象，对象在传输之前就要序列化，这个序列化的过程就是编码过程。接收到编码后的数据就需要解码，还原传输的数据。

编解码技术就是java序列化技术，序列化的目的有两个，一是进行网络传输，二是对象持久化。

但是Java的序列化缺点很多，如无法跨语言，序列化后码流太大，序列化性能太低

主流的序列化框架：

　　JBoss的Marshalling包

　　google的Protobuf

　　基于Protobuf的Kyro

　　MessagePack框架

JBoss Marshalling的实现

代码示例：

public class Server {

    public static void main(String[] args) throws Exception {

        EventLoopGroup pGroup = new NioEventLoopGroup();
        EventLoopGroup cGroup = new NioEventLoopGroup();

        ServerBootstrap b = new ServerBootstrap();
        b.group(pGroup, cGroup).channel(NioServerSocketChannel.class).option(ChannelOption.SO_BACKLOG, 1024)
                // 设置日志
                .handler(new LoggingHandler(LogLevel.INFO)).childHandler(new ChannelInitializer<SocketChannel>() {
                    protected void initChannel(SocketChannel sc) throws Exception {
                        sc.pipeline().addLast(MarshallingCodeCFactory.buildMarshallingDecoder());
                        sc.pipeline().addLast(MarshallingCodeCFactory.buildMarshallingEncoder());
                        sc.pipeline().addLast(new ServerHandler());
                    }
                });

        ChannelFuture cf = b.bind(8765).sync();

        cf.channel().closeFuture().sync();
        pGroup.shutdownGracefully();
        cGroup.shutdownGracefully();

    }
}


public class ServerHandler extends ChannelHandlerAdapter {

    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {

    }

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        Req req = (Req) msg;
        System.out.println("Server : " + req.getId() + ", " + req.getName() + ", " + req.getRequestMessage());
        byte[] attachment = GzipUtils.ungzip(req.getAttachment());

        String path = System.getProperty("user.dir") + File.separatorChar + "receive" + File.separatorChar + "001.jpg";
        FileOutputStream fos = new FileOutputStream(path);
        fos.write(attachment);
        fos.close();

        Resp resp = new Resp();
        resp.setId(req.getId());
        resp.setName("resp" + req.getId());
        resp.setResponseMessage("响应内容" + req.getId());
        ctx.writeAndFlush(resp);// .addListener(ChannelFutureListener.CLOSE);
    }

    @Override
    public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {

    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        ctx.close();
    }

}


public class Client {

    public static void main(String[] args) throws Exception {

        EventLoopGroup group = new NioEventLoopGroup();
        Bootstrap b = new Bootstrap();
        b.group(group).channel(NioSocketChannel.class).handler(new ChannelInitializer<SocketChannel>() {
            @Override
            protected void initChannel(SocketChannel sc) throws Exception {
                sc.pipeline().addLast(MarshallingCodeCFactory.buildMarshallingDecoder());
                sc.pipeline().addLast(MarshallingCodeCFactory.buildMarshallingEncoder());
                sc.pipeline().addLast(new ClientHandler());
            }
        });

        ChannelFuture cf = b.connect("127.0.0.1", 8765).sync();

        for (int i = 0; i < 5; i++) {
            Req req = new Req();
            req.setId("" + i);
            req.setName("pro" + i);
            req.setRequestMessage("数据信息" + i);
            String path = System.getProperty("user.dir") + File.separatorChar + "sources" + File.separatorChar
                    + "001.jpg";
            File file = new File(path);
            FileInputStream in = new FileInputStream(file);
            byte[] data = new byte[in.available()];
            in.read(data);
            in.close();
            req.setAttachment(GzipUtils.gzip(data));
            cf.channel().writeAndFlush(req);
        }

        cf.channel().closeFuture().sync();
        group.shutdownGracefully();
    }
}


public class ClientHandler extends ChannelHandlerAdapter {

    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {

    }

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        try {
            Resp resp = (Resp) msg;
            System.out.println("Client : " + resp.getId() + ", " + resp.getName() + ", " + resp.getResponseMessage());
        } finally {
            ReferenceCountUtil.release(msg);
        }
    }

    @Override
    public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {

    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        ctx.close();
    }

}


/**
 * Marshalling工厂
 * 
 */
public final class MarshallingCodeCFactory {

    /**
     * 创建Jboss Marshalling解码器MarshallingDecoder
     * 
     * @return MarshallingDecoder
     */
    public static MarshallingDecoder buildMarshallingDecoder() {
        // 首先通过Marshalling工具类的精通方法获取Marshalling实例对象 参数serial标识创建的是java序列化工厂对象。
        final MarshallerFactory marshallerFactory = Marshalling.getProvidedMarshallerFactory("serial");
        // 创建了MarshallingConfiguration对象，配置了版本号为5
        final MarshallingConfiguration configuration = new MarshallingConfiguration();
        configuration.setVersion(5);
        // 根据marshallerFactory和configuration创建provider
        UnmarshallerProvider provider = new DefaultUnmarshallerProvider(marshallerFactory, configuration);
        // 构建Netty的MarshallingDecoder对象，俩个参数分别为provider和单个消息序列化后的最大长度
        MarshallingDecoder decoder = new MarshallingDecoder(provider, 1024 * 1024 * 1);
        return decoder;
    }

    /**
     * 创建Jboss Marshalling编码器MarshallingEncoder
     * 
     * @return MarshallingEncoder
     */
    public static MarshallingEncoder buildMarshallingEncoder() {
        final MarshallerFactory marshallerFactory = Marshalling.getProvidedMarshallerFactory("serial");
        final MarshallingConfiguration configuration = new MarshallingConfiguration();
        configuration.setVersion(5);
        MarshallerProvider provider = new DefaultMarshallerProvider(marshallerFactory, configuration);
        // 构建Netty的MarshallingEncoder对象，MarshallingEncoder用于实现序列化接口的POJO对象序列化为二进制数组
        MarshallingEncoder encoder = new MarshallingEncoder(provider);
        return encoder;
    }
}

public class Req implements Serializable {

    private static final long serialVersionUID = 1L;

    private String id;
    private String name;
    private String requestMessage;
    private byte[] attachment;

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getRequestMessage() {
        return requestMessage;
    }

    public void setRequestMessage(String requestMessage) {
        this.requestMessage = requestMessage;
    }

    public byte[] getAttachment() {
        return attachment;
    }

    public void setAttachment(byte[] attachment) {
        this.attachment = attachment;
    }
}

public class Resp implements Serializable {

    private static final long serialVersionUID = 1L;

    private String id;
    private String name;
    private String responseMessage;

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getResponseMessage() {
        return responseMessage;
    }

    public void setResponseMessage(String responseMessage) {
        this.responseMessage = responseMessage;
    }

}

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