前言

之前的Netty利用json和LineBasedFrameDecoder和StringDecoder来实现数据传输和解决粘包/半包问题。后来发现Netty支持更高效的编解码例如MessagePack。本篇主要来讲讲MessagePack的使用。

MessagePack优点

MessagePack是一个高效的二进制序列化框架

和json一样支持跨语言
序列化之后的码流更小
编解码性能高效

Netty客户端–MessagePack编解码

Netty提供了丰富的编解码器抽象基类，我们可以很容易的实现这些基类来自定义编解码器。

Netty客户端–MessagePack编码

这里将需要编码的对象加上@Message注解
我之前 result属性用的是Object 因为返回类型可能是List或者Map或者String等但是在MessagePack中不能使用Object 类型所有我改成了String。

@Message
public class RPCRequest {
    private String requestID;
    private String className;
    private String methodName;
    private String[] parameters;
    private String result;
    public String getRequestID() {
        return requestID;
    }
    public void setRequestID(String requestID) {
        this.requestID = requestID;
    }
    public String getClassName() {
        return className;
    }
    public void setClassName(String className) {
        this.className = className;
    }
    public String getMethodName() {
        return methodName;
    }
    public void setMethodName(String methodName) {
        this.methodName = methodName;
    }
    public String[] getParameters() {
        return parameters;
    }
    public void setParameters(String[] parameters) {
        this.parameters = parameters;
    }
    public String getResult() {
        return result;
    }
    public void setResult(String result) {
        this.result = result;
    }
}

利用Netty基类来自定义编码器

public class ClientMsgPackEncode extends MessageToByteEncoder<Object>{
    @Override
    protected void encode(ChannelHandlerContext arg0, Object msg, ByteBuf out)
            throws Exception {
            RPCRequest request = (RPCRequest) msg;
            MessagePack msgPack = new MessagePack();
            //msgPack.register(RPCRequest.class);
            byte[] raw = null;
            raw = msgPack.write(request);
            out.writeBytes(raw);    
    }
}

Netty客户端–MessagePack解码

@Message
public class RPCResponse {
    private String requestID;
    private String result;
    public String getRequestID() {
        return requestID;
    }
    public void setRequestID(String requestID) {
        this.requestID = requestID;
    }
    public String getResult() {
        return result;
    }
    public void setResult(String result) {
        this.result = result;
    }
}

利用Netty基类来自定义解码器

public class ClientMsgPackDecode extends MessageToMessageDecoder<ByteBuf>{
    @Override
    protected void decode(ChannelHandlerContext arg0, ByteBuf msg,
            List<Object> out) throws Exception {
        // TODO Auto-generated method stub
        final byte[] array;
        final int length = msg.readableBytes();
        array = new byte[length];
        msg.getBytes(msg.readerIndex(), array, 0, length);
        MessagePack msgPack = new MessagePack();
        out.add(msgPack.read(array,RPCResponse.class));
    }
}

Netty客户端–编解码使用

在链路里添加

ch.pipeline().addLast(new LengthFieldBasedFrameDecoder(65535, 0, 2,0,2));
ch.pipeline().addLast(new LengthFieldPrepender(2));
ch.pipeline().addLast(new ClientMsgPackEncode());//编码
ch.pipeline().addLast(new ClientMsgPackDecode());//解码
ch.pipeline().addLast(new RPCRequestHandler());//添加相应回调处理和编解码器

之后的发送消息和读取消息可以直接使用对象

Netty服务端–MessagePack编解码

说明一下客户端服务端用了2套的原因是编解码的时候对象不是同一个
例如客户端编码是RPCRequest对象服务端编码RPCResponse 对象。

Netty服务端–MessagePack解码

public class ServerMsgPackDecode extends MessageToMessageDecoder<ByteBuf>{
    @Override
    protected void decode(ChannelHandlerContext arg0, ByteBuf msg,
            List<Object> out) throws Exception {
        // TODO Auto-generated method stub
        final byte[] array;
        final int length = msg.readableBytes();
        array = new byte[length];
        msg.getBytes(msg.readerIndex(), array, 0, length);
        MessagePack msgPack = new MessagePack();
        out.add(msgPack.read(array,RPCRequest.class));
    }
}

Netty服务端–MessagePack编码

public class ServerMsgPackEncode extends MessageToByteEncoder<Object>{
    @Override
    protected void encode(ChannelHandlerContext arg0, Object msg, ByteBuf out)
            throws Exception {
        RPCResponse RPCResponse = (RPCResponse) msg;
        MessagePack msgPack = new MessagePack();
        //msgPack.register(RPCResponse.class);
        byte[] raw = null;
        raw = msgPack.write(RPCResponse);
        out.writeBytes(raw);    
    }
}

Netty服务端–编解码使用

同样在链路里添加

socketChannel.pipeline().addLast(new LengthFieldBasedFrameDecoder(65535, 0, 2,0,2));//编码
socketChannel.pipeline().addLast(new LengthFieldPrepender(2));
socketChannel.pipeline().addLast(new ServerMsgPackEncode());//编码
socketChannel.pipeline().addLast(new ServerMsgPackDecode());//解码
socketChannel.pipeline().addLast(new RPCResponseHandler());//处理类