netty之编解码

　　1、netty的编码和解码，在数据传输的时候，考虑数据安全，数据完整性都是很有必要的。这里主要是介绍netty3和netty5的编解码方式。其实从StringEncoder和StringDecoder中也可以获取源码的编解码规则。然后改变成自己的编解码规则也是可以的。

　　2、netty3和netty5的编解码方式还是存在一定差别的。个人感觉netty5来的更加实用和方便。

　　3、netty3的编解码规则

　　1）数据编码规则（我这里只是用于显示，数据规则很简单）

　　包头+模块+数据（请求编解码）

　　包头+模块+状态+数据（响应编解码）

　　2）目录

　　

　　3）请求和相应对象

package com.troy.data.domain;

//请求数据
public class Request {

    //模块类型
    private int model;
    //数据
    private byte[] data;

    public int getModel() {
        return model;
    }

    public void setModel(int model) {
        this.model = model;
    }

    public byte[] getData() {
        return data;
    }

    public void setData(byte[] data) {
        this.data = data;
    }

    @Override
    public String toString() {
        return "Request{" +
                "model=" + model +
                ", data=" + new String(data) +
                '}';
    }
}

package com.troy.data.domain;

import java.util.Arrays;

//响应数据
public class Response {

    //模块类型
    private int model;
    //状态码
    private int status;
    //数据
    private byte[] data;


    public int getModel() {
        return model;
    }

    public void setModel(int model) {
        this.model = model;
    }

    public int getStatus() {
        return status;
    }

    public void setStatus(int status) {
        this.status = status;
    }

    public byte[] getData() {
        return data;
    }

    public void setData(byte[] data) {
        this.data = data;
    }

    @Override
    public String toString() {
        return "Response{" +
                "model=" + model +
                ", status=" + status +
                ", data=" + new String(data) +
                '}';
    }
}

　　4）常量（这里的包头，因为是固定的就写了一个常量）

package com.troy.data.constant;

//常量
public class ConsantUtil {

    //固定常量用于数据拼接，确认
    public static final int PACKAGE_HEADER = -32523523;

}

　　5）请求编解码

package com.troy.data.codec;

import com.troy.data.constant.ConsantUtil;
import com.troy.data.domain.Request;
import org.jboss.netty.buffer.ChannelBuffer;
import org.jboss.netty.buffer.ChannelBuffers;
import org.jboss.netty.channel.Channel;
import org.jboss.netty.channel.ChannelHandlerContext;
import org.jboss.netty.handler.codec.oneone.OneToOneEncoder;

public class RequestEncode extends OneToOneEncoder {

    protected Object encode(ChannelHandlerContext channelHandlerContext, Channel channel, Object o) throws Exception {

        Request request = (Request) o;
        ChannelBuffer channelBuffer = ChannelBuffers.dynamicBuffer();
        channelBuffer.writeInt(ConsantUtil.PACKAGE_HEADER);
        channelBuffer.writeInt(ConsantUtil.PACKAGE_HEADER);
        channelBuffer.writeBytes(request.getData());
        return channelBuffer;
    }
}

package com.troy.data.codec;

import com.troy.data.constant.ConsantUtil;
import com.troy.data.domain.Request;
import org.jboss.netty.buffer.ChannelBuffer;
import org.jboss.netty.channel.Channel;
import org.jboss.netty.channel.ChannelHandlerContext;
import org.jboss.netty.handler.codec.oneone.OneToOneDecoder;

//请求数据解码
public class RequestDecode extends OneToOneDecoder {

    protected Object decode(ChannelHandlerContext channelHandlerContext, Channel channel, Object o) throws Exception {
        ChannelBuffer channelBuffer = (ChannelBuffer) o;
        if (ConsantUtil.PACKAGE_HEADER == channelBuffer.readInt()) {
            Request request = new Request();
            request.setModel(channelBuffer.readInt());
            byte[] bytes = new byte[channelBuffer.readableBytes()];
            channelBuffer.readBytes(bytes);
            request.setData(bytes);
            return request;
        }
        return null;
    }
}

　　6）响应编解码

package com.troy.data.codec;

import com.troy.data.constant.ConsantUtil;
import com.troy.data.domain.Response;
import org.jboss.netty.buffer.ChannelBuffer;
import org.jboss.netty.buffer.ChannelBuffers;
import org.jboss.netty.channel.Channel;
import org.jboss.netty.channel.ChannelHandlerContext;
import org.jboss.netty.handler.codec.oneone.OneToOneEncoder;

//响应编码器
public class ResponseEncode extends OneToOneEncoder {

    protected Object encode(ChannelHandlerContext channelHandlerContext, Channel channel, Object o) throws Exception {
        Response response = (Response) o;
        ChannelBuffer channelBuffer = ChannelBuffers.dynamicBuffer();
        channelBuffer.writeInt(ConsantUtil.PACKAGE_HEADER);
        channelBuffer.writeInt(response.getModel());
        channelBuffer.writeInt(response.getStatus());
        channelBuffer.writeBytes(response.getData());
        return channelBuffer;
    }
}

package com.troy.data.codec;

import com.troy.data.constant.ConsantUtil;
import com.troy.data.domain.Response;
import org.jboss.netty.buffer.ChannelBuffer;
import org.jboss.netty.channel.Channel;
import org.jboss.netty.channel.ChannelHandlerContext;
import org.jboss.netty.handler.codec.oneone.OneToOneDecoder;

//响应解码
public class ResponseDecode extends OneToOneDecoder{

    protected Object decode(ChannelHandlerContext channelHandlerContext, Channel channel, Object o) throws Exception {
            ChannelBuffer channelBuffer = (ChannelBuffer) o;
        if (ConsantUtil.PACKAGE_HEADER == channelBuffer.readInt()) {
            Response response = new Response();
            response.setModel(channelBuffer.readInt());
            response.setStatus(channelBuffer.readInt());
            byte[] bytes = new byte[channelBuffer.readableBytes()];
            channelBuffer.readBytes(bytes);
            response.setData(bytes);
            return response;
        }
        return null;
    }
}

　　7）设置对应的管道编解码就可以了

　　a、客户端

　　　　 //设置管道工厂
        clientBootstrap.setPipelineFactory(new ChannelPipelineFactory() {

            public ChannelPipeline getPipeline() throws Exception {
                ChannelPipeline channelPipeline = Channels.pipeline();
                channelPipeline.addLast("decode",new RequestEncode());
                channelPipeline.addLast("encode",new ResponseDecode());
                channelPipeline.addLast("client",new ClientHandler());
                return channelPipeline;
            }
        });

　　@Override
    public void messageReceived(ChannelHandlerContext ctx, MessageEvent e) throws Exception {
        Response response = (Response) e.getMessage();
        System.out.println(response.toString());
        super.messageReceived(ctx, e);
    }

　　b、服务端

        //设置管道流
        serverBootstrap.setPipelineFactory(new ChannelPipelineFactory() {

            public ChannelPipeline getPipeline() throws Exception {
                ChannelPipeline channelPipeline = Channels.pipeline();
                //添加处理方式
                channelPipeline.addLast("idle",new IdleStateHandler(new HashedWheelTimer(),60,60,60));
                channelPipeline.addLast("decode",new RequestDecode());
                channelPipeline.addLast("encode",new ResponseEncode());
                channelPipeline.addLast("server",new ServerHandler());
                return channelPipeline;
            }
        });        

　　@Override
    public void messageReceived(ChannelHandlerContext ctx, MessageEvent e) throws Exception {
        Request request = (Request) e.getMessage();
        System.out.println("client:"+request.toString());
        Response response = new Response();
        response.setModel(1);
        response.setStatus(1);
        response.setData("hello client".getBytes());
        ctx.getChannel().write(response);
        super.messageReceived(ctx, e);
    }

　　4、netty5的编解码规则

　　1）数据结构、目录结构、对象、常量都是一样。

　　2）编解码的编写方式有些不一样

　　a、请求编解码

package com.troy.data.codec;

import com.troy.data.constant.ConsantUtil;
import com.troy.data.domain.Request;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandler;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.MessageToMessageEncoder;

import java.util.List;
@ChannelHandler.Sharable
public class RequestEncode extends MessageToMessageEncoder<Request> {

    protected void encode(ChannelHandlerContext channelHandlerContext, Request request, List<Object> list) throws Exception {
        ByteBuf byteBuf = Unpooled.buffer();
        byteBuf.writeInt(ConsantUtil.PACKAGE_HEADER);
        byteBuf.writeInt(request.getModel());
        byteBuf.writeBytes(request.getData());
        list.add(byteBuf);
    }
}

package com.troy.data.codec;

import com.troy.data.constant.ConsantUtil;
import com.troy.data.domain.Request;
import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandler;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.MessageToMessageDecoder;

import java.util.List;

//请求数据解码
@ChannelHandler.Sharable
public class RequestDecode extends MessageToMessageDecoder<ByteBuf>{

    protected void decode(ChannelHandlerContext channelHandlerContext, ByteBuf byteBuf, List<Object> list) throws Exception {
        if (ConsantUtil.PACKAGE_HEADER == byteBuf.readInt()) {
            //当数据超过指定值的时候跳过这部分数据
            if (byteBuf.readableBytes() > 2048) {
                byteBuf.skipBytes(byteBuf.readableBytes());
            }
            //一个字节一个字节的读取，知道读取到包头
            while(true) {
                byteBuf.markReaderIndex();
                if (ConsantUtil.PACKAGE_HEADER == byteBuf.readInt()) {
                    break;
                }
                byteBuf.resetReaderIndex();
                byteBuf.readByte();
            }
            Request request = new Request();
            request.setModel(byteBuf.readInt());
            byte[] bytes = new byte[byteBuf.readableBytes()];
            byteBuf.readBytes(bytes);
            request.setData(bytes);
            list.add(request);
        }
    }
}

　　b、响应编解码

package com.troy.data.codec;

import com.troy.data.constant.ConsantUtil;
import com.troy.data.domain.Response;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandler;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.MessageToMessageEncoder;

import java.util.List;

//响应编码器
@ChannelHandler.Sharable
public class ResponseEncode extends MessageToMessageEncoder<Response> {

    protected void encode(ChannelHandlerContext channelHandlerContext, Response response, List<Object> list) throws Exception {
        ByteBuf byteBuf = Unpooled.buffer();
        byteBuf.writeInt(ConsantUtil.PACKAGE_HEADER);
        byteBuf.writeInt(response.getModel());
        byteBuf.writeInt(response.getStatus());
        byteBuf.writeBytes(response.getData());
        list.add(byteBuf);
    }
}

package com.troy.data.codec;

import com.troy.data.constant.ConsantUtil;
import com.troy.data.domain.Response;
import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandler;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.MessageToMessageDecoder;

import java.util.List;

//响应解码
@ChannelHandler.Sharable
public class ResponseDecode extends MessageToMessageDecoder<ByteBuf>{

    protected void decode(ChannelHandlerContext channelHandlerContext, ByteBuf byteBuf, List<Object> list) throws Exception {
        if (ConsantUtil.PACKAGE_HEADER == byteBuf.readInt()) {
            //当数据超过指定值的时候跳过这部分数据
            if (byteBuf.readableBytes() > 2048) {
                byteBuf.skipBytes(byteBuf.readableBytes());
            }
            //一个字节一个字节的读取，知道读取到包头
            while(true) {
                byteBuf.markReaderIndex();
                if (ConsantUtil.PACKAGE_HEADER == byteBuf.readInt()) {
                    break;
                }
                byteBuf.resetReaderIndex();
                byteBuf.readByte();
            }
            Response response = new Response();
            response.setModel(byteBuf.readInt());
            response.setStatus(byteBuf.readInt());
            byte[] bytes = new byte[byteBuf.readableBytes()];
            byteBuf.readBytes(bytes);
            response.setData(bytes);
            list.add(response);
        }
    }
}

　　3）处理上面基本上都是一样的。

　　5、netty的编解码，主要目的就是处理通讯问题，对数据进行自定义处理！

 　　6、源码下载：https://pan.baidu.com/s/1nvUnmEt