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Netty中定长×××的使用

有了前面的基础，定长×××的使用相对就比较简单了，所以这里只使用服务端的代码，测试时，用telnet作为客户客户端，数据只作单向的发送，即从客户端到服务端。

服务端

EchoServer.java

package cn.xpleaf.netty02;import io.netty.bootstrap.ServerBootstrap;import io.netty.buffer.ByteBuf;import io.netty.buffer.Unpooled;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;import io.netty.handler.codec.DelimiterBasedFrameDecoder;import io.netty.handler.codec.FixedLengthFrameDecoder;import io.netty.handler.codec.string.StringDecoder;public class EchoServer {    public void bind(int port) throws Exception {        // 配置服务端的NIO线程组        EventLoopGroup bossGroup = new NioEventLoopGroup();        EventLoopGroup workerGroup = new NioEventLoopGroup();        try {            ServerBootstrap b = new ServerBootstrap();            b.group(bossGroup, workerGroup)                .channel(NioServerSocketChannel.class)                .option(ChannelOption.SO_BACKLOG, 1024)                .childHandler(new ChannelInitializer
    
     () {                    @Override                    protected void initChannel(SocketChannel ch) throws Exception {                        // 添加定长分隔符×××到pipeline中，长度设置为20                        ch.pipeline().addLast(new FixedLengthFrameDecoder(20));                        // 添加StringDecoder×××，将ByteBuf解码成字符串对象                        ch.pipeline().addLast(new StringDecoder());                        // 添加业务处理handler                        ch.pipeline().addLast(new EchoServerHandler());                    }                });            // 绑定端口，同步等待成功            ChannelFuture f = b.bind(port).sync();            // 等待服务端监听端口关闭            f.channel().closeFuture().sync();        } finally {            // 优雅退出，释放线程池资源            bossGroup.shutdownGracefully();            workerGroup.shutdownGracefully();        }    }    public static void main(String[] args) throws Exception {        int port = 8080;        if(args != null && args.length > 0) {            try {                port = Integer.valueOf(port);            } catch (NumberFormatException e) {                // TODO: handle exception            }        }        new EchoServer().bind(port);    }}
    

EchoServerHandler.java

package cn.xpleaf.netty02;import io.netty.buffer.ByteBuf;import io.netty.buffer.Unpooled;import io.netty.channel.ChannelHandlerAdapter;import io.netty.channel.ChannelHandlerContext;import io.netty.channel.ChannelInboundHandlerAdapter;public class EchoServerHandler extends ChannelInboundHandlerAdapter {    private int counter = 0;    @Override    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {        String body = (String) msg;        System.out.println("Receive client : [" + body + "]");    }    @Override    public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {        ctx.flush();    }    @Override    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {        // 发生异常，关闭链路        ctx.close();    }}

测试

启动服务端，在telnet客户端中输入相应字符串：

yeyonghao@yeyonghaodeMacBook-Pro:~$ telnet localhost 8080Trying ::1...Connected to localhost.Escape character is '^]'.Ye Yonghao welcome to Beijing

此时查看服务端的输出：

Receive client : [Ye Yonghao welcome t]

可以看到中括号时字符数刚好是20个，因为在pipeline中设置定长×××时，设置的长度就是20。

可以尝试再发送消息：

yeyonghao@yeyonghaodeMacBook-Pro:~$ telnet localhost 8080Trying ::1...Connected to localhost.Escape character is '^]'.Ye Yonghao welcome to BeijingI love you so much!

再查看服务端的输出：

Receive client : [Ye Yonghao welcome t]Receive client : [o BeijingI love yo]

可以看到服务端把上一次的消息作为这次消息的开始，包括换行符，这说明定长×××确实是有效果了。