Netty入门二 之解编码

关键字：Netty解编码，JBoss Marshalling，

代码在 https://github.com/zhaikaishun/NettyTutorial 在SocketIO_02 kaishun.netty.serial下

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Netty解编码技术

解编码技术，说白了就是java序列化技术，序列化的目的就两个，第一进行网络传输，第二对象持久化
虽然我们可以使用java进行对象序列化，netty去传输，但是java序列化的硬伤太多，比如java序列化没法跨语言、序列化够码流太大、序列化性能太低等等…
主流的编码解码框架：
JBoss 的 Marshalling包
google的Protobuf
给予Protobuf的Kyro
MessagePack框架

JBoss Marshalling

Jboss Marshalling是一个java对象序列化包，对jdk默认的序列化框架进行了优化，但又保持跟java.io.Serializable接口的兼容，同时增加了一些可调的参数和附加特性，
类库 jboss-marshalling-1.3.0、jboss-marshalling-serial-1.3.0
Jboss Marshalling与Netty结合后进行序列化对象的代码编写非常简单，我们一起来看一下

首先有个MarshallingCodeCFactory类
这个类不需要看懂，就要有一个这个类就好了

/** * Marshalling工厂 * @author（alienware） * @since 2014-12-16 */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;    }}

Server端其他基本不变，就这里

         .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());            }        });

Client端也是这里有变化

         .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());            }        });        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);        }

Req类

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;    }}

Resp类

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;    }}

ClientHandler

    @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);        }    }

ServerHandler

    @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);    }

总结上面的代码：
其实只需要在Server和Client端加上这两个，其他方法还是一样的。

                sc.pipeline().addLast(MarshallingCodeCFactory.buildMarshallingDecoder());                sc.pipeline().addLast(MarshallingCodeCFactory.buildMarshallingEncoder());

补充： 如果还想进行大文件（例如图片视频等传输），将上面的注释的代码打开即可，这块代码还使用了Gzip进行压缩，压缩之后再进行传输，这是需要注意的。

特别感谢互联网架构师白鹤翔老师，本文大多出自他的视频讲解。
笔者主要是记录笔记，以便之后翻阅，正所谓好记性不如烂笔头，烂笔头不如云笔记