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netty报错address is used netty outboundhandler

1.Netty中handler的执行顺序 

  Handler在Netty中,无疑占据着非常重要的地位。Handler与Servlet中的filter很像,通过Handler可以完成通讯报文的解码编码、拦截指定的报文、

统一对日志错误进行处理、统一对请求进行计数、控制Handler执行与否。一句话,没有它做不到的只有你想不到的

  Netty中的所有handler都实现自ChannelHandler接口。按照输入输出来分,分为ChannelInboundHandler、ChannelOutboundHandler两大类

ChannelInboundHandler对从客户端发往服务器的报文进行处理,一般用来执行解码、读取客户端数据、进行业务处理等;ChannelOutboundHandler

对从服务器发往客户端的报文进行处理,一般用来进行编码、发送报文到客户端

  Netty中可以注册多个handler。ChannelInboundHandler按照注册的先后顺序执行;ChannelOutboundHandler按照注册的先后顺序逆序执行

如下图所示,按照注册的先后顺序对Handler进行排序,request进入Netty后的执行顺序为:

netty报错address is used netty outboundhandler,netty报错address is used netty outboundhandler_.net,第1张

 

 

2.Netty中handler执行顺序代码示例:

客户端代码同上

服务端代码及业务逻辑类:

 

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;/**
 * • 配置服务器功能,如线程、端口 • 实现服务器处理程序,它包含业务逻辑,决定当有一个请求连接或接收数据时该做什么
 */
public class EchoServer {
    private final int port;
    public EchoServer(int port) {
        this.port = port;
    }

    public void start() throws Exception {
        EventLoopGroup eventLoopGroup = null;
        try {
            //server端引导类
            ServerBootstrap serverBootstrap = new ServerBootstrap();
            //连接池处理数据
            eventLoopGroup = new NioEventLoopGroup();
            serverBootstrap.group(eventLoopGroup)
            .channel(NioServerSocketChannel.class)//指定通道类型为NioServerSocketChannel,一种异步模式,OIO阻塞模式为OioServerSocketChannel
            .localAddress("localhost",port)//设置InetSocketAddress让服务器监听某个端口已等待客户端连接。
            .childHandler(new ChannelInitializer<Channel>() {//设置childHandler执行所有的连接请求
                @Override
                protected void initChannel(Channel ch) throws Exception {
                    // 注册两个InboundHandler,执行顺序为注册顺序,所以应该是InboundHandler1 InboundHandler2
                    ch.pipeline().addLast(new EchoOutHandler1());
                    ch.pipeline().addLast(new EchoOutHandler2()); 
                    // 注册两个OutboundHandler,执行顺序为注册顺序的逆序,所以应该是OutboundHandler2 OutboundHandler1
                    ch.pipeline().addLast(new EchoInHandler1());
                    ch.pipeline().addLast(new EchoInHandler2());
                }
                    });
            // 最后绑定服务器等待直到绑定完成,调用sync()方法会阻塞直到服务器完成绑定,然后服务器等待通道关闭,因为使用sync(),所以关闭操作也会被阻塞。
            ChannelFuture channelFuture = serverBootstrap.bind().sync();
            System.out.println("开始监听,端口为:" + channelFuture.channel().localAddress());
            channelFuture.channel().closeFuture().sync();
        } finally {
            eventLoopGroup.shutdownGracefully().sync();
        }
    }

    public static void main(String[] args) throws Exception {
        new EchoServer(20000).start();
    }
}

 

业务类EchoInHandler1:

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;

import java.util.Date;

import cn.itcast_03_netty.sendobject.bean.Person;

public class EchoInHandler1 extends ChannelInboundHandlerAdapter {

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg)
            throws Exception {
        System.out.println("in1");
         // 通知执行下一个InboundHandler
        ctx.fireChannelRead(msg);//ChannelInboundHandler之间的传递,通过调用 ctx.fireChannelRead(msg) 实现
    }

    @Override
    public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
        ctx.flush();//刷新后才将数据发出到SocketChannel
    }

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

业务类 EchoInHandler2:

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import java.util.Date;

public class EchoInHandler2 extends ChannelInboundHandlerAdapter {

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        System.out.println("in2");
        ByteBuf buf = (ByteBuf) msg;
        byte[] req = new byte[buf.readableBytes()];
        buf.readBytes(req);
        String body = new String(req, "UTF-8");
        System.out.println("接收客户端数据:" + body);
        //向客户端写数据
        System.out.println("server向client发送数据");
        String currentTime = new Date(System.currentTimeMillis()).toString();
        ByteBuf resp = Unpooled.copiedBuffer(currentTime.getBytes());
        ctx.write(resp); //用ctx.write(msg) 将传递到 ChannelOutboundHandler
    }

    @Override
    public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
        ctx.flush();//刷新后才将数据发出到SocketChannel
    }

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

业务逻辑类 EchoOutHandler2:

import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelOutboundHandlerAdapter;
import io.netty.channel.ChannelPromise;

public class EchoOutHandler2 extends ChannelOutboundHandlerAdapter {

     @Override
        public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception {
            System.out.println("out2");
            // 执行下一个OutboundHandler
            super.write(ctx, msg, promise);
        }
}

业务逻辑类 EchoOutHandler1:

import java.util.Date;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelOutboundHandlerAdapter;
import io.netty.channel.ChannelPromise;

public class EchoOutHandler1 extends ChannelOutboundHandlerAdapter {
    @Override
    // 向client发送消息
    public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception {
        System.out.println("out1");
        String currentTime = new Date(System.currentTimeMillis()).toString();
        ByteBuf resp = Unpooled.copiedBuffer(currentTime.getBytes());
        ctx.write(resp);
        ctx.flush(); //ctx.write()方法执行后,需要调用flush()方法才能令它立即执行
       }
}

运行结果:

开始监听,端口为:/127.0.0.1:20000
in1
in2
接收客户端数据:QUERY TIME ORDER
server向client发送数据
out2
out1

总结: 

在使用Handler的过程中,需要注意:

1、ChannelInboundHandler之间的传递,通过调用 ctx.fireChannelRead(msg) 实现;调用ctx.write(msg) 将传递到ChannelOutboundHandler

ctx.write()方法执行后,需要调用flush()方法才能令它立即执行。

ChannelOutboundHandler 在注册的时候需要放在最后一个ChannelInboundHandler之前,否则将无法传递到ChannelOutboundHandler

   (流水线pipeline中outhander不能放到最后,否则不生效)

Handler的消费处理放在最后一个处理。

 

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