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3.Netty的粘包、拆包（二）

时间：2018-10-12 23:36:20      阅读：162      评论：0      收藏：0      [点我收藏+]

标签：ide   情况   http   客户端   使用   服务端   close   ima   变化   

Netty提供的TCP数据拆包、粘包解决方案

1.前言

关于TCP的数据拆包、粘包的介绍，我在上一篇文章里面已经有过介绍。

想要了解一下的，请点击这里 Chick Here！

今天我们要讲解的是Netty提供的两种解决方案：

  1. DelimiterBasedFrameDecoder
  2. FixedLengthFrameDecoder

2.关于Decoder

  1. 先观察下两段代码的不同

    （1）使用StringDecoder之前

    @Override
 public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {


     try {

         ByteBuf in = (ByteBuf) msg;
         String str = in.toString(CharsetUtil.UTF_8);
         System.out.println("Client:"+str);

     } finally {
         ReferenceCountUtil.release(msg);
     }
 }

    （2）使用StringDecoder之后

    @Override
 public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {


     try {
         String str = (String) msg;
         System.out.println("Client:"+str);

     } finally {
         ReferenceCountUtil.release(msg);
     }
 }

  2. 关于Decoder

    decoder：n. 解码器

    在我看来，Netty数据的解析方式大概为：

    发送过程：Buffer------>数据报------>比特流

    接受过程：Buffer<------数据报<------比特流

    所以我们接受到的msg是一个ButeBuf

    使用了Decoder（这里使用StringDecoder举例）之后：

    发送过程：Buffer------>数据报------>比特流

    接受过程：String<------Buffer<------数据报<------比特流

    相当于ByteBuf按照StringDecoder的解码规则，把msg翻译成为了一个字符串。

  3. 如何使用Decoder

    （1）实际代码演示：

    package com.xm.netty.demo02;

import java.net.InetSocketAddress;

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.Channel;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.handler.codec.string.StringDecoder;

public class Server {

 private final int port;

 public Server(int port) {
     this.port = port;
 }



 public static void main(String[] args) {

     int port = 8989;
     try {
         new Server(port).start();
     } catch (InterruptedException e) {
         // TODO Auto-generated catch block
         e.printStackTrace();
     }

 }



 private void start() throws InterruptedException {
     EventLoopGroup g1 = new NioEventLoopGroup();
     EventLoopGroup g2 = new NioEventLoopGroup();
     try {
         ServerBootstrap bootstrap = new ServerBootstrap();
          bootstrap
                 .group(g1,g2)
                 .channel(NioServerSocketChannel.class)
                 .localAddress(new InetSocketAddress( port))
                 .childHandler(new ChannelInitializer() {
                     @Override
                     protected void initChannel(Channel ch) throws Exception {
                         ch.pipeline().addLast(new StringDecoder());
                         ch.pipeline().addLast(new ServerHandler());
                     }
                 });
          ChannelFuture future = bootstrap.bind().sync();
          future.channel().closeFuture().sync();
     } finally {
         g1.shutdownGracefully().sync();
         g2.shutdownGracefully().sync();
     }
 }

}

    代码改动：

    ch.pipeline().addLast(new StringDecoder());
    ?

    ? ch.pipeline().addLast(new ServerHandler());

    （2）多个Decoder的使用顺序：

    从前往后，依次解码

    ?

    假设我们有个通过字符串变化为时间的TimeDecoder：

    ch.pipeline().addLast(new StringDecoder());

    ch.pipeline().addLast(new TimeDecoder());

    ? ch.pipeline().addLast(new ServerHandler());

    解析规则为：

    技术分享图片

3.DelimiterBasedFrameDecoder

  1. 关于DelimiterBasedFrameDecoder

    其实很简单，就是在一个缓冲区的末尾添加一个结束字符。

    在规定了最大长度的缓冲区里，遇到一个特殊字符，就截取一次。

    原理类似于String的split（）方法。

  2. 代码实现

    （1）服务端Server

    package com.xm.netty.demo03;

import java.net.InetSocketAddress;

import io.netty.bootstrap.ServerBootstrap;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.Channel;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.handler.codec.DelimiterBasedFrameDecoder;
import io.netty.handler.codec.string.StringDecoder;

public class Server {

 private final int port;

 public Server(int port) {
     this.port = port;
 }



 public static void main(String[] args) {

     int port = 8989;
     try {
         new Server(port).start();
     } catch (InterruptedException e) {
         // TODO Auto-generated catch block
         e.printStackTrace();
     }

 }



 private void start() throws InterruptedException {
     EventLoopGroup g1 = new NioEventLoopGroup();
     EventLoopGroup g2 = new NioEventLoopGroup();
     try {
         ServerBootstrap bootstrap = new ServerBootstrap();
          bootstrap
                 .group(g1,g2)
                 .channel(NioServerSocketChannel.class)
                 .localAddress(new InetSocketAddress( port))
                 .childHandler(new ChannelInitializer() {
                     @Override
                     protected void initChannel(Channel ch) throws Exception {
                         ByteBuf buf = Unpooled.copiedBuffer("$".getBytes());
                         ch.pipeline().addLast(new DelimiterBasedFrameDecoder(1024,buf));
                         ch.pipeline().addLast(new StringDecoder());
                         ch.pipeline().addLast(new ServerHandler());
                     }
                 });
          ChannelFuture future = bootstrap.bind().sync();
          future.channel().closeFuture().sync();
     } finally {
         g1.shutdownGracefully().sync();
         g2.shutdownGracefully().sync();
     }
 }

}

    （2）服务端ServerHandler

    package com.xm.netty.demo03;

import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerAdapter;
import io.netty.channel.ChannelHandlerContext;
import io.netty.util.CharsetUtil;

public class ServerHandler extends ChannelHandlerAdapter {

 @Override
 public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {

     String str = (String) msg;
     System.out.println("Server:"+str);
     str = "服务器返回--->"+ str+"$";
     ctx.writeAndFlush(Unpooled.copiedBuffer(str.getBytes()));
 }

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

 @Override
 public void channelActive(ChannelHandlerContext ctx) throws Exception {
     System.out.println(DateTimeFormatter.ISO_LOCAL_DATE_TIME.format(LocalDateTime.now())+"一个客户端连接上服务器！");
 }


}

    （3）客户端Client

    package com.xm.netty.demo03;

import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;

import io.netty.bootstrap.Bootstrap;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.codec.DelimiterBasedFrameDecoder;
import io.netty.handler.codec.string.StringDecoder;

public class Client {

 private final int port;
 private final String host;



 public Client(int port, String host) {
     this.port = port;
     this.host = host;
 }

 public static void main(String[] args) {
     String host = "127.0.0.1";
     int port = 8989;
     try {
         new Client(port, host).start();
     } catch (InterruptedException e) {
         // TODO Auto-generated catch block
         e.printStackTrace();
     }
 }

 private void start() throws InterruptedException {

     EventLoopGroup group = new NioEventLoopGroup();
     try {
         Bootstrap bootstrap = new Bootstrap();
         bootstrap
                 .group(group)
                 .channel(NioSocketChannel.class)
                 .remoteAddress(host, port)
                 .handler(new ChannelInitializer<SocketChannel>() {

                     @Override
                     protected void initChannel(SocketChannel ch) throws Exception {
                         ByteBuf buf = Unpooled.copiedBuffer("$".getBytes());
                         ch.pipeline().addLast(new DelimiterBasedFrameDecoder(1024,buf));
                         ch.pipeline().addLast(new StringDecoder());
                         ch.pipeline().addLast(new ClientHandler());
                     }

                 });

         ChannelFuture future = bootstrap.connect().sync();

         for(int i=10;i<20;i++) {
             String str = DateTimeFormatter.ISO_LOCAL_DATE_TIME.format(LocalDateTime.now()) + "---- " +i+"<<<$";
             future.channel().write(Unpooled.copiedBuffer(str.getBytes()));
         }

         future.channel().flush();


         //future.channel().writeAndFlush(Unpooled.copiedBuffer("Hello Netty!".getBytes()));



         future.channel().closeFuture().sync();
     } finally {
         group.shutdownGracefully().sync();
     }

 }

}

    （4）客户端ClientHandler

    package com.xm.netty.demo03;

import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerAdapter;
import io.netty.channel.ChannelHandlerContext;
import io.netty.util.CharsetUtil;
import io.netty.util.ReferenceCountUtil;

public class ClientHandler extends ChannelHandlerAdapter {

 @Override
 public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {


     try {
         String str = (String) msg;
         System.out.println("Client:"+str);

     } finally {
         ReferenceCountUtil.release(msg);
     }
 }

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

 @Override
 public void channelActive(ChannelHandlerContext ctx) throws Exception {
     System.out.println(DateTimeFormatter.ISO_LOCAL_DATE_TIME.format(LocalDateTime.now())+"已连接服务器！");
 }


}

  3. 运行结果截图

    （1）服务端运行结果：

    技术分享图片

    （2）客户端运行结果：

    技术分享图片

4.FixedLengthFrameDecoder

  1. 关于FixedLengthFrameDecoder

    其实很简单，就是对规定的发送的数据进行限制长度，

    当符合这个长度的情况下，就可以解析。

    假设你发送一个’123456‘，’654321‘

    那么解析的状况为’12345‘，’66543‘

  2. 代码实现

    （1）服务端Server

    package com.xm.netty.demo04;

import java.net.InetSocketAddress;

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.Channel;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.handler.codec.FixedLengthFrameDecoder;
import io.netty.handler.codec.string.StringDecoder;

public class Server {

 private final int port;

 public Server(int port) {
     this.port = port;
 }



 public static void main(String[] args) {

     int port = 8989;
     try {
         new Server(port).start();
     } catch (InterruptedException e) {
         // TODO Auto-generated catch block
         e.printStackTrace();
     }

 }



 private void start() throws InterruptedException {
     EventLoopGroup g1 = new NioEventLoopGroup();
     EventLoopGroup g2 = new NioEventLoopGroup();
     try {
         ServerBootstrap bootstrap = new ServerBootstrap();
          bootstrap
                 .group(g1,g2)
                 .channel(NioServerSocketChannel.class)
                 .localAddress(new InetSocketAddress( port))
                 .childHandler(new ChannelInitializer() {
                     @Override
                     protected void initChannel(Channel ch) throws Exception {
                         ch.pipeline().addLast(new FixedLengthFrameDecoder(5));
                         ch.pipeline().addLast(new StringDecoder());
                         ch.pipeline().addLast(new ServerHandler());
                     }
                 });
          ChannelFuture future = bootstrap.bind().sync();
          future.channel().closeFuture().sync();
     } finally {
         g1.shutdownGracefully().sync();
         g2.shutdownGracefully().sync();
     }
 }

}

    （2）服务端ServerHandler

    package com.xm.netty.demo04;

import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerAdapter;
import io.netty.channel.ChannelHandlerContext;
import io.netty.util.CharsetUtil;

public class ServerHandler extends ChannelHandlerAdapter {

 @Override
 public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {

     String str = (String) msg;
     System.out.println("Server:"+str);
     ctx.writeAndFlush(Unpooled.copiedBuffer(str.getBytes()));
 }

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

 @Override
 public void channelActive(ChannelHandlerContext ctx) throws Exception {
     System.out.println(DateTimeFormatter.ISO_LOCAL_DATE_TIME.format(LocalDateTime.now())+"一个客户端连接上服务器！");
 }


}

    （3）客户端Client

    package com.xm.netty.demo04;

import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;

import io.netty.bootstrap.Bootstrap;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.codec.FixedLengthFrameDecoder;
import io.netty.handler.codec.string.StringDecoder;

public class Client {

 private final int port;
 private final String host;



 public Client(int port, String host) {
     this.port = port;
     this.host = host;
 }

 public static void main(String[] args) {
     String host = "127.0.0.1";
     int port = 8989;
     try {
         new Client(port, host).start();
     } catch (InterruptedException e) {
         // TODO Auto-generated catch block
         e.printStackTrace();
     }
 }

 private void start() throws InterruptedException {

     EventLoopGroup group = new NioEventLoopGroup();
     try {
         Bootstrap bootstrap = new Bootstrap();
         bootstrap
                 .group(group)
                 .channel(NioSocketChannel.class)
                 .remoteAddress(host, port)
                 .handler(new ChannelInitializer<SocketChannel>() {

                     @Override
                     protected void initChannel(SocketChannel ch) throws Exception {
                         ch.pipeline().addLast(new FixedLengthFrameDecoder(5));
                         ch.pipeline().addLast(new StringDecoder());
                         ch.pipeline().addLast(new ClientHandler());
                     }

                 });

         ChannelFuture future = bootstrap.connect().sync();

         for(int i=123450;i<123460;i++) {
             String str = ""+i;
             future.channel().write(Unpooled.copiedBuffer(str.getBytes()));
         }
         future.channel().flush();

         //future.channel().writeAndFlush(Unpooled.copiedBuffer("Hello Netty!".getBytes()));



         future.channel().closeFuture().sync();
     } finally {
         group.shutdownGracefully().sync();
     }

 }

}

    （4）客户端ClientHandler

    package com.xm.netty.demo04;

import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerAdapter;
import io.netty.channel.ChannelHandlerContext;
import io.netty.util.CharsetUtil;
import io.netty.util.ReferenceCountUtil;

public class ClientHandler extends ChannelHandlerAdapter {

 @Override
 public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {


     try {
         String str = (String) msg;
         System.out.println("Client:"+str);

     } finally {
         ReferenceCountUtil.release(msg);
     }
 }

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

 @Override
 public void channelActive(ChannelHandlerContext ctx) throws Exception {
     System.out.println(DateTimeFormatter.ISO_LOCAL_DATE_TIME.format(LocalDateTime.now())+"已连接服务器！");
 }


}

  3. 运行结果截图

    （1）服务端运行结果：

    技术分享图片

    （2）客户端运行结果：

    技术分享图片

3.Netty的粘包、拆包（二）

标签：ide   情况   http   客户端   使用   服务端   close   ima   变化   

原文地址：https://www.cnblogs.com/TimerHotel/p/netty03.html
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