一、定义类,继承MessageToMessageCodec,重写encode和decode方法
package cn.edu.tju;import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.MessageToMessageCodec;import java.util.List;public class MyMessageToMessageCodec extends MessageToMessageCodec<ByteBuf, String> {@Overrideprotected void encode(ChannelHandlerContext channelHandlerContext, String s, List<Object> list) throws Exception {System.out.println("encode was called......");ByteBuf buf = Unpooled.copiedBuffer(s.getBytes());list.add(buf);}@Overrideprotected void decode(ChannelHandlerContext channelHandlerContext, ByteBuf byteBuf, List<Object> list) throws Exception {System.out.println("decode was called......");int length = byteBuf.readableBytes();byte[] bytes = new byte[length];byteBuf.readBytes(bytes);String str = new String (bytes);list.add(str);System.out.println("codec received message: " + str);}
}
二、定义一个简单的ChannelInboundHandlerAdapter
package cn.edu.tju;import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;public class MySimpleHandler2 extends ChannelInboundHandlerAdapter {@Overridepublic void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {String str = (String)msg;System.out.println("handler received message: " + msg);ctx.channel().writeAndFlush(str.toUpperCase());}
}
三、定义netty TCP server 主类,在ChannelPipeline中加入上述两个handler
package cn.edu.tju;import io.netty.bootstrap.ServerBootstrap;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.*;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.handler.codec.DelimiterBasedFrameDecoder;
import io.netty.handler.codec.FixedLengthFrameDecoder;
import io.netty.handler.codec.LengthFieldBasedFrameDecoder;
import io.netty.handler.codec.LineBasedFrameDecoder;
import io.netty.handler.codec.string.StringDecoder;import java.net.InetSocketAddress;public class NettyTcpServer11 {public static void main(String[] args) {EventLoopGroup bossGroup = new NioEventLoopGroup(1);EventLoopGroup workerGroup = new NioEventLoopGroup(16);try {ServerBootstrap serverBootstrap = new ServerBootstrap();serverBootstrap.group(bossGroup, workerGroup);serverBootstrap.channel(NioServerSocketChannel.class);serverBootstrap.childHandler(new ChannelInitializer<SocketChannel>() {@Overrideprotected void initChannel(SocketChannel ch) throws Exception {ChannelPipeline pipeline = ch.pipeline();pipeline.addLast(new MyMessageToMessageCodec());pipeline.addLast(new MySimpleHandler2());}});ChannelFuture channelFuture = serverBootstrap.bind(new InetSocketAddress(8899)).sync();channelFuture.channel().closeFuture().sync();} catch (Exception ex){System.out.println(ex.getMessage());bossGroup.shutdownGracefully();workerGroup.shutdownGracefully();}}
}
MessageToMessageCodec的子类可以用@Sharable注解标记。
ByteToMessageCodec的子类不能用@Sharable注解标记,因为在调用构造方法时会判断是否有@Sharable注解,如果有,会报错。