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Netty4.0学习笔记系列之二:Handler的执行顺序(转)
http://blog.csdn.net/u013252773/article/details/21195593
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。按照输出输出来分,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:
基本的概念就说到这,下面用一个例子来进行验证。该例子模拟Client与Server间的通讯,Server端注册了2个ChannelInboundHandler、2个ChannelOutboundHandler。当Client连接到Server后,会向Server发送一条消息。Server端通过ChannelInboundHandler 对Client发送的消息进行读取,通过ChannelOutboundHandler向client发送消息。最后Client把接收到的信息打印出来。
Server端一共有5个类:HelloServer InboundHandler1 InboundHandler2 OutboundHandler1 OutboundHandler2
1、HelloServer 代码如下
- package com.guowl.testmultihandler;
- import io.netty.bootstrap.ServerBootstrap;
- import io.netty.channel.ChannelFuture;
- import io.netty.channel.ChannelInitializer;
- import io.netty.channel.ChannelOption;
- import io.netty.channel.EventLoopGroup;
- import io.netty.channel.nio.NioEventLoopGroup;
- import io.netty.channel.socket.SocketChannel;
- import io.netty.channel.socket.nio.NioServerSocketChannel;
- public class HelloServer {
- public void start(int port) throws Exception {
- EventLoopGroup bossGroup = new NioEventLoopGroup();
- EventLoopGroup workerGroup = new NioEventLoopGroup();
- try {
- ServerBootstrap b = new ServerBootstrap();
- b.group(bossGroup, workerGroup).channel(NioServerSocketChannel.class)
- .childHandler(new ChannelInitializer<SocketChannel>() {
- @Override
- public void initChannel(SocketChannel ch) throws Exception {
- // 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 OutboundHandler1());
- ch.pipeline().addLast(new OutboundHandler2());
- // 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 InboundHandler1());
- ch.pipeline().addLast(new InboundHandler2());
- }
- }).option(ChannelOption.SO_BACKLOG, 128)
- .childOption(ChannelOption.SO_KEEPALIVE, true);
- ChannelFuture f = b.bind(port).sync();
- f.channel().closeFuture().sync();
- } finally {
- workerGroup.shutdownGracefully();
- bossGroup.shutdownGracefully();
- }
- }
- public static void main(String[] args) throws Exception {
- HelloServer server = new HelloServer();
- server.start(8000);
- }
- }
2、InboundHandler1
- package com.guowl.testmultihandler;
- import io.netty.channel.ChannelHandlerContext;
- import io.netty.channel.ChannelInboundHandlerAdapter;
- import org.slf4j.Logger;
- import org.slf4j.LoggerFactory;
- public class InboundHandler1 extends ChannelInboundHandlerAdapter {
- private static Logger logger = LoggerFactory.getLogger(InboundHandler1.class);
- @Override
- public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
- logger.info("InboundHandler1.channelRead: ctx :" + ctx);
- // 通知执行下一个InboundHandler
- ctx.fireChannelRead(msg);
- }
- @Override
- public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
- logger.info("InboundHandler1.channelReadComplete");
- ctx.flush();
- }
- }
3、InboundHandler2
- package com.guowl.testmultihandler;
- import io.netty.buffer.ByteBuf;
- import io.netty.channel.ChannelHandlerContext;
- import io.netty.channel.ChannelInboundHandlerAdapter;
- import org.slf4j.Logger;
- import org.slf4j.LoggerFactory;
- public class InboundHandler2 extends ChannelInboundHandlerAdapter {
- private static Logger logger = LoggerFactory.getLogger(InboundHandler2.class);
- @Override
- // 读取Client发送的信息,并打印出来
- public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
- logger.info("InboundHandler2.channelRead: ctx :" + ctx);
- ByteBuf result = (ByteBuf) msg;
- byte[] result1 = new byte[result.readableBytes()];
- result.readBytes(result1);
- String resultStr = new String(result1);
- System.out.println("Client said:" + resultStr);
- result.release();
- ctx.write(msg);
- }
- @Override
- public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
- logger.info("InboundHandler2.channelReadComplete");
- ctx.flush();
- }
- }
4、OutboundHandler1
- package com.guowl.testmultihandler;
- import io.netty.buffer.ByteBuf;
- import io.netty.channel.ChannelHandlerContext;
- import io.netty.channel.ChannelOutboundHandlerAdapter;
- import io.netty.channel.ChannelPromise;
- import org.slf4j.Logger;
- import org.slf4j.LoggerFactory;
- public class OutboundHandler1 extends ChannelOutboundHandlerAdapter {
- private static Logger logger = LoggerFactory.getLogger(OutboundHandler1.class);
- @Override
- // 向client发送消息
- public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception {
- logger.info("OutboundHandler1.write");
- String response = "I am ok!";
- ByteBuf encoded = ctx.alloc().buffer(4 * response.length());
- encoded.writeBytes(response.getBytes());
- ctx.write(encoded);
- ctx.flush();
- }
- }
5、OutboundHandler2
- package com.guowl.testmultihandler;
- import io.netty.channel.ChannelHandlerContext;
- import io.netty.channel.ChannelOutboundHandlerAdapter;
- import io.netty.channel.ChannelPromise;
- import org.slf4j.Logger;
- import org.slf4j.LoggerFactory;
- public class OutboundHandler2 extends ChannelOutboundHandlerAdapter {
- private static Logger logger = LoggerFactory.getLogger(OutboundHandler2.class);
- @Override
- public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception {
- logger.info("OutboundHandler2.write");
- // 执行下一个OutboundHandler
- super.write(ctx, msg, promise);
- }
- }
Client端有两个类:HelloClient HelloClientIntHandler
1、HelloClient
- package com.guowl.testmultihandler;
- import io.netty.bootstrap.Bootstrap;
- import io.netty.channel.ChannelFuture;
- import io.netty.channel.ChannelInitializer;
- import io.netty.channel.ChannelOption;
- import io.netty.channel.EventLoopGroup;
- import io.netty.channel.nio.NioEventLoopGroup;
- import io.netty.channel.socket.SocketChannel;
- import io.netty.channel.socket.nio.NioSocketChannel;
- public class HelloClient {
- public void connect(String host, int port) throws Exception {
- EventLoopGroup workerGroup = new NioEventLoopGroup();
- try {
- Bootstrap b = new Bootstrap();
- b.group(workerGroup);
- b.channel(NioSocketChannel.class);
- b.option(ChannelOption.SO_KEEPALIVE, true);
- b.handler(new ChannelInitializer<SocketChannel>() {
- @Override
- public void initChannel(SocketChannel ch) throws Exception {
- ch.pipeline().addLast(new HelloClientIntHandler());
- }
- });
- // Start the client.
- ChannelFuture f = b.connect(host, port).sync();
- f.channel().closeFuture().sync();
- } finally {
- workerGroup.shutdownGracefully();
- }
- }
- public static void main(String[] args) throws Exception {
- HelloClient client = new HelloClient();
- client.connect("127.0.0.1", 8000);
- }
- }
2、HelloClientIntHandler
- package com.guowl.testmultihandler;
- import io.netty.buffer.ByteBuf;
- import io.netty.channel.ChannelHandlerContext;
- import io.netty.channel.ChannelInboundHandlerAdapter;
- import org.slf4j.Logger;
- import org.slf4j.LoggerFactory;
- public class HelloClientIntHandler extends ChannelInboundHandlerAdapter {
- private static Logger logger = LoggerFactory.getLogger(HelloClientIntHandler.class);
- @Override
- // 读取服务端的信息
- public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
- logger.info("HelloClientIntHandler.channelRead");
- ByteBuf result = (ByteBuf) msg;
- byte[] result1 = new byte[result.readableBytes()];
- result.readBytes(result1);
- result.release();
- ctx.close();
- System.out.println("Server said:" + new String(result1));
- }
- @Override
- // 当连接建立的时候向服务端发送消息 ,channelActive 事件当连接建立的时候会触发
- public void channelActive(ChannelHandlerContext ctx) throws Exception {
- logger.info("HelloClientIntHandler.channelActive");
- String msg = "Are you ok?";
- ByteBuf encoded = ctx.alloc().buffer(4 * msg.length());
- encoded.writeBytes(msg.getBytes());
- ctx.write(encoded);
- ctx.flush();
- }
- }
server端执行结果为:
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。
2、ctx.write()方法执行后,需要调用flush()方法才能令它立即执行。
3、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。
Netty4.0学习笔记系列之二:Handler的执行顺序(转)