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.java
package com.bijian.netty.dto; import java.io.Serializable; public class Person implements Serializable { private static final long serialVersionUID = 1L; private String name; private String sex; private int age; public String toString() { return "name:" + name + " sex:" + sex + " age:" + age; } public String getName() { return name; } public void setName(String name) { this.name = name; } public String getSex() { return sex; } public void setSex(String sex) { this.sex = sex; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } }
Server端的类为:Server.java、PersonDecoder.java、StringDecoder.java、BusinessHandler.java
1.Server.java开启Netty服务
package com.bijian.netty.server; 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; // 测试coder 和 handler 的混合使用 public class Server { 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() { @Override public void initChannel(SocketChannel ch) throws Exception { ch.pipeline().addLast(new PersonDecoder()); ch.pipeline().addLast(new StringDecoder()); ch.pipeline().addLast(new BusinessHandler()); } }).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 { Server server = new Server(); server.start(8000); } }
2.PersonDecoder.java把二进制流转换成Person对象
package com.bijian.netty.server; import io.netty.buffer.ByteBuf; import io.netty.channel.ChannelHandlerContext; import io.netty.handler.codec.ByteToMessageDecoder; import java.util.List; import com.bijian.netty.util.ByteBufToBytes; import com.bijian.netty.util.ByteObjConverter; public class PersonDecoder extends ByteToMessageDecoder { @Override protected void decode(ChannelHandlerContext ctx, ByteBuf in, List
3.StringDecoder.java把满足条件的字符串转换成Person对象
package com.bijian.netty.server; import io.netty.buffer.ByteBuf; import io.netty.channel.ChannelHandlerContext; import io.netty.handler.codec.ByteToMessageDecoder; import java.util.List; import com.bijian.netty.dto.Person; import com.bijian.netty.util.ByteBufToBytes; public class StringDecoder extends ByteToMessageDecoder { @Override protected void decode(ChannelHandlerContext ctx, ByteBuf in, List
4.BusinessHandler.java展现客户端请求的内容
package com.bijian.netty.server; import io.netty.channel.ChannelHandlerContext; import io.netty.channel.ChannelInboundHandlerAdapter; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import com.bijian.netty.dto.Person; public class BusinessHandler extends ChannelInboundHandlerAdapter { private Logger logger = LoggerFactory.getLogger(BusinessHandler.class); @Override public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception { Person person = (Person) msg; logger.info("BusinessHandler read msg from client :" + person); } @Override public void channelReadComplete(ChannelHandlerContext ctx) throws Exception { ctx.flush(); } @Override public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception { ctx.close(); } }
客户端1发送Person格式的协议:Client.java、ClientInitHandler.java、PersonEncoder.java
1.Client.java
package com.bijian.netty.client; 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; import com.bijian.netty.dto.Person; public class Client { 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() { @Override public void initChannel(SocketChannel ch) throws Exception { ch.pipeline().addLast(new PersonEncoder()); Person person = new Person(); person.setName("test"); person.setSex("man"); person.setAge(30); ch.pipeline().addLast(new ClientInitHandler(person)); } }); ChannelFuture f = b.connect(host, port).sync(); f.channel().closeFuture().sync(); } finally { workerGroup.shutdownGracefully(); } } public static void main(String[] args) throws Exception { Client client = new Client(); client.connect("127.0.0.1", 8000); } }
2.ClientInitHandler.java向服务端发送Person对象
package com.bijian.netty.client; import io.netty.channel.ChannelHandlerContext; import io.netty.channel.ChannelInboundHandlerAdapter; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import com.bijian.netty.dto.Person; public class ClientInitHandler extends ChannelInboundHandlerAdapter { private static Logger logger = LoggerFactory.getLogger(ClientInitHandler.class); private Person person; public ClientInitHandler(Person person) { this.person = person; } @Override public void channelActive(ChannelHandlerContext ctx) throws Exception { logger.info("ClientInitHandler.channelActive"); ctx.write(person); ctx.flush(); } }
3.PersonEncoder.java把Person对象转换成二进制进行传送
package com.bijian.netty.client; import io.netty.buffer.ByteBuf; import io.netty.channel.ChannelHandlerContext; import io.netty.handler.codec.MessageToByteEncoder; import com.bijian.netty.dto.Person; import com.bijian.netty.util.ByteObjConverter; public class PersonEncoder extends MessageToByteEncoder{ @Override protected void encode(ChannelHandlerContext ctx, Person msg, ByteBuf out) throws Exception { out.writeBytes(ByteObjConverter.ObjectToByte(msg)); } }
客户端2发送String格式的协议:Client2.java、StringEncoder.java同样使用了客户端1中定义的ClientInitHandler 进行数据发送操作。
1.Client2.java
package com.bijian.netty.client; 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; import com.bijian.netty.dto.Person; public class Client2 { 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() { @Override public void initChannel(SocketChannel ch) throws Exception { ch.pipeline().addLast(new StringEncoder()); Person person = new Person(); person.setName("test2"); person.setSex("girl"); person.setAge(4); ch.pipeline().addLast(new ClientInitHandler(person)); } }); ChannelFuture f = b.connect(host, port).sync(); f.channel().closeFuture().sync(); } finally { workerGroup.shutdownGracefully(); } } public static void main(String[] args) throws Exception { Client2 client = new Client2(); client.connect("127.0.0.1", 8000); } }
2.StringEncoder.java把Person对象转换成固定格式的String的二进制流进行传送
package com.bijian.netty.client; import io.netty.buffer.ByteBuf; import io.netty.channel.ChannelHandlerContext; import io.netty.handler.codec.MessageToByteEncoder; import com.bijian.netty.dto.Person; public class StringEncoder extends MessageToByteEncoder{ @Override protected void encode(ChannelHandlerContext ctx, Person msg, ByteBuf out) throws Exception { // 转成字符串:name:xx;age:xx;sex:xx; StringBuffer sb = new StringBuffer(); sb.append("name:").append(msg.getName()).append(";"); sb.append("age:").append(msg.getAge()).append(";"); sb.append("sex:").append(msg.getSex()).append(";"); out.writeBytes(sb.toString().getBytes()); } }
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。
文章来源:http://blog.csdn.net/u013252773/article/details/22108385