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上文介绍了如何应用Netty开发自定义通讯协议,本文在此基础上进一步深化,研究如何同时支持不同的通讯协议。
此处所谓的通讯协议,指的是把Netty通讯管道中的二进制流转换为对象、把对象转换成二进制流的过程。转换过程追根究底还是ChannelInboundHandler、ChannelOutboundHandler的实现类在进行处理。ChannelInboundHandler负责把二进制流转换为对象,ChannelOutboundHandler负责把对象转换为二进制流。
接下来要构建一个Server,同时支持Person通讯协议和String通讯协议。
- Person通讯协议:二进制流与Person对象间的互相转换。
- String通讯协议:二进制流与有固定格式要求的String的相互转换。String格式表示的也是一个Person对象,格式规定为:name:xx;age:xx;sex:xx;
这时候,来自客户端的请求,会依次传递给两个通讯解析接口进行解析,每个通讯接口判断是否是匹配的协议,如果是则进行解析,如果不是则传递给其它通讯接口进行解析。
实体类:Person
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package com.guowl.testobjcoder;
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import java.io.Serializable;
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public class Person implements Serializable{
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private static final long serialVersionUID = 1L;
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private String name;
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private String sex;
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private int age;
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public String toString() {
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return "name:" + name + " sex:" + sex + " age:" + age;
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}
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public String getName() {
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return name;
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}
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public void setName(String name) {
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this.name = name;
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}
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public String getSex() {
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return sex;
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}
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public void setSex(String sex) {
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this.sex = sex;
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}
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public int getAge() {
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return age;
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}
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public void setAge(int age) {
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this.age = age;
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}
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}
Server端的类为:Server PersonDecoder StringDecoder BusinessHandler
1、Server 开启Netty服务
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package com.guowl.testobjcoder;
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import io.netty.bootstrap.ServerBootstrap;
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import io.netty.channel.ChannelFuture;
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import io.netty.channel.ChannelInitializer;
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import io.netty.channel.ChannelOption;
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import io.netty.channel.EventLoopGroup;
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import io.netty.channel.nio.NioEventLoopGroup;
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import io.netty.channel.socket.SocketChannel;
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import io.netty.channel.socket.nio.NioServerSocketChannel;
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public class Server {
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public void start(int port) throws Exception {
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EventLoopGroup bossGroup = new NioEventLoopGroup();
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EventLoopGroup workerGroup = new NioEventLoopGroup();
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try {
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ServerBootstrap b = new ServerBootstrap();
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b.group(bossGroup, workerGroup).channel(NioServerSocketChannel.class)
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.childHandler(new ChannelInitializer<SocketChannel>() {
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@Override
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public void initChannel(SocketChannel ch) throws Exception {
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ch.pipeline().addLast(new PersonDecoder());
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ch.pipeline().addLast(new StringDecoder());
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ch.pipeline().addLast(new BusinessHandler());
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}
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}).option(ChannelOption.SO_BACKLOG, 128).childOption(ChannelOption.SO_KEEPALIVE, true);
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ChannelFuture f = b.bind(port).sync();
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f.channel().closeFuture().sync();
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} finally {
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workerGroup.shutdownGracefully();
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bossGroup.shutdownGracefully();
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}
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}
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public static void main(String[] args) throws Exception {
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Server server = new Server();
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server.start(8000);
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}
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}
2、PersonDecoder 把二进制流转换成Person对象
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package com.guowl.testobjcoder;
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import io.netty.buffer.ByteBuf;
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import io.netty.channel.ChannelHandlerContext;
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import io.netty.handler.codec.ByteToMessageDecoder;
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import java.util.List;
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import com.guowl.utils.ByteBufToBytes;
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import com.guowl.utils.ByteObjConverter;
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public class PersonDecoder extends ByteToMessageDecoder {
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@Override
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protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception {
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byte n = "n".getBytes()[0];
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byte p = in.readByte();
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in.resetReaderIndex();
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if (n != p) {
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ByteBufToBytes reader = new ByteBufToBytes();
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out.add(ByteObjConverter.byteToObject(reader.read(in)));
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} else {
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ctx.fireChannelRead(in);
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}
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}
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}
3、StringDecoder 把满足条件的字符串转换成Person对象
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package com.guowl.testobjcoder;
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import io.netty.buffer.ByteBuf;
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import io.netty.channel.ChannelHandlerContext;
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import io.netty.handler.codec.ByteToMessageDecoder;
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import java.util.List;
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import com.guowl.utils.ByteBufToBytes;
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public class StringDecoder extends ByteToMessageDecoder {
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@Override
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protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception {
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byte n = "n".getBytes()[0];
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byte p = in.readByte();
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in.resetReaderIndex();
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if (n == p) {
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ByteBufToBytes reader = new ByteBufToBytes();
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String msg = new String(reader.read(in));
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Person person = buildPerson(msg);
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out.add(person);
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} else {
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ctx.fireChannelRead(in);
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}
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}
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private Person buildPerson(String msg) {
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Person person = new Person();
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String[] msgArray = msg.split(";|:");
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person.setName(msgArray[1]);
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person.setAge(Integer.parseInt(msgArray[3]));
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person.setSex(msgArray[5]);
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return person;
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}
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}
4、BusinessHandler 展现客户端请求的内容
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package com.guowl.testobjcoder;
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import io.netty.channel.ChannelHandlerContext;
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import io.netty.channel.ChannelInboundHandlerAdapter;
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import org.slf4j.Logger;
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import org.slf4j.LoggerFactory;
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public class BusinessHandler extends ChannelInboundHandlerAdapter {
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private Logger logger = LoggerFactory.getLogger(BusinessHandler.class);
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@Override
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public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
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Person person = (Person) msg;
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logger.info("BusinessHandler read msg from client :" + person);
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}
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@Override
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public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
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ctx.flush();
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}
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<span style="white-space:pre"> </span>
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<pre name="code" class="java"><span style="white-space:pre"> </span>@Override
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public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
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ctx.close();
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}
}
客户端1发送Person格式的协议:Client ClientInitHandler PersonEncoder
1、Client
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package com.guowl.testobjcoder;
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import io.netty.bootstrap.Bootstrap;
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import io.netty.channel.ChannelFuture;
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import io.netty.channel.ChannelInitializer;
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import io.netty.channel.ChannelOption;
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import io.netty.channel.EventLoopGroup;
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import io.netty.channel.nio.NioEventLoopGroup;
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import io.netty.channel.socket.SocketChannel;
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import io.netty.channel.socket.nio.NioSocketChannel;
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public class Client {
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public void connect(String host, int port) throws Exception {
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EventLoopGroup workerGroup = new NioEventLoopGroup();
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try {
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Bootstrap b = new Bootstrap();
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b.group(workerGroup);
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b.channel(NioSocketChannel.class);
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b.option(ChannelOption.SO_KEEPALIVE, true);
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b.handler(new ChannelInitializer<SocketChannel>() {
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@Override
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public void initChannel(SocketChannel ch) throws Exception {
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ch.pipeline().addLast(new PersonEncoder());
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Person person = new Person();
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person.setName("guowl");
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person.setSex("man");
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person.setAge(30);
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ch.pipeline().addLast(new ClientInitHandler(person));
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}
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});
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ChannelFuture f = b.connect(host, port).sync();
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f.channel().closeFuture().sync();
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} finally {
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workerGroup.shutdownGracefully();
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}
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}
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public static void main(String[] args) throws Exception {
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Client client = new Client();
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client.connect("127.0.0.1", 8000);
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}
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}
2、ClientInitHandler 向服务端发送Person对象
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package com.guowl.testobjcoder;
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import io.netty.channel.ChannelHandlerContext;
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import io.netty.channel.ChannelInboundHandlerAdapter;
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import org.slf4j.Logger;
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import org.slf4j.LoggerFactory;
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public class ClientInitHandler extends ChannelInboundHandlerAdapter {
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private static Logger logger = LoggerFactory.getLogger(ClientInitHandler.class);
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private Person person;
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public ClientInitHandler(Person person){
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this.person = person;
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}
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@Override
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public void channelActive(ChannelHandlerContext ctx) throws Exception {
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logger.info("ClientInitHandler.channelActive");
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ctx.write(person);
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ctx.flush();
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}
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}
3、PersonEncoder 把Person对象转换成二进制进行传送
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package com.guowl.testobjcoder;
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import com.guowl.utils.ByteObjConverter;
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import io.netty.buffer.ByteBuf;
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import io.netty.channel.ChannelHandlerContext;
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import io.netty.handler.codec.MessageToByteEncoder;
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public class PersonEncoder extends MessageToByteEncoder<Person> {
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@Override
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protected void encode(ChannelHandlerContext ctx, Person msg, ByteBuf out) throws Exception {
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out.writeBytes(ByteObjConverter.objectToByte(msg));
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}
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}
客户端2发送String格式的协议:Client2 StringEncoder 同样使用了客户端1中定义的ClientInitHandler 进行数据发送操作。
1、Client2
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package com.guowl.testobjcoder.client2;
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import io.netty.bootstrap.Bootstrap;
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import io.netty.channel.ChannelFuture;
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import io.netty.channel.ChannelInitializer;
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import io.netty.channel.ChannelOption;
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import io.netty.channel.EventLoopGroup;
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import io.netty.channel.nio.NioEventLoopGroup;
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import io.netty.channel.socket.SocketChannel;
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import io.netty.channel.socket.nio.NioSocketChannel;
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import com.guowl.testobjcoder.ClientInitHandler;
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import com.guowl.testobjcoder.Person;
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public class Client2 {
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public void connect(String host, int port) throws Exception {
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EventLoopGroup workerGroup = new NioEventLoopGroup();
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try {
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Bootstrap b = new Bootstrap();
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b.group(workerGroup);
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b.channel(NioSocketChannel.class);
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b.option(ChannelOption.SO_KEEPALIVE, true);
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b.handler(new ChannelInitializer<SocketChannel>() {
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@Override
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public void initChannel(SocketChannel ch) throws Exception {
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ch.pipeline().addLast(new StringEncoder());
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Person person = new Person();
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person.setName("guoxy");
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person.setSex("girl");
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person.setAge(4);
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ch.pipeline().addLast(new ClientInitHandler(person));
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}
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});
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ChannelFuture f = b.connect(host, port).sync();
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f.channel().closeFuture().sync();
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} finally {
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workerGroup.shutdownGracefully();
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}
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}
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public static void main(String[] args) throws Exception {
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Client2 client = new Client2();
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client.connect("127.0.0.1", 8000);
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}
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}
2、StringEncoder 把Person对象转换成固定格式的String的二进制流进行传送
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package com.guowl.testobjcoder.client2;
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import io.netty.buffer.ByteBuf;
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import io.netty.channel.ChannelHandlerContext;
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import io.netty.handler.codec.MessageToByteEncoder;
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import com.guowl.testobjcoder.Person;
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public class StringEncoder extends MessageToByteEncoder<Person> {
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@Override
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protected void encode(ChannelHandlerContext ctx, Person msg, ByteBuf out) throws Exception {
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StringBuffer sb = new StringBuffer();
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sb.append("name:").append(msg.getName()).append(";");
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sb.append("age:").append(msg.getAge()).append(";");
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sb.append("sex:").append(msg.getSex()).append(";");
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out.writeBytes(sb.toString().getBytes());
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}
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}
其它:工具类ByteBufToBytes(读取ByteBuf数据的工具类)、ByteObjConverter(Object与byte互转的工具类)在以前的文章中已经存在,在此省略。
注意事项:
1、该段代码能运行出结果,但是运行的时候会报 io.netty.util.IllegalReferenceCountException: refCnt: 0, decrement: 1 异常,已经解决。日志中的提示信息为:
An exceptionCaught() event was fired, and it reached at the tail of the pipeline. It usually means the last handler in the pipeline did not handle the exception
说明缺少exceptionCaught方法,在server端最后一个Handler中增加这个方法即可。
2、PersonDecoder和StringDecoder中有一个if判断,是为了判断消息究竟是什么协议。如果是String协议的话,格式是【name:xx;age:xx;sex:xx;】,第一个字母是英文字母n,所以判断协议类型时候是读取二进制流的第一个字符进行判断,当然这种判断方式非常幼稚,以后有机会可以进行改善。
Netty4.0学习笔记系列之六:多种通讯协议支持
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原文地址:http://blog.csdn.net/bbaiggey/article/details/51812124