Netty 学习笔记二 ByteToMessageDecoder使用

来源：互联网发布：2016年cpi年度数据编辑：程序博客网时间：2024/05/20 09:05

服务端使用上节的 Netty Time服务端

对客户端进行改写：

package io.netty.example.time;import java.util.List;import io.netty.buffer.ByteBuf;import io.netty.channel.ChannelHandlerContext;import io.netty.handler.codec.ByteToMessageDecoder;public class TimeDecoder extends ByteToMessageDecoder { // (1)    @Override    protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) { // (2)        if (in.readableBytes()<4) {            return; // (3)        }        out.add(in.readBytes(4)); // (4)    }}

package io.netty.example.time;import io.netty.buffer.ByteBuf;import io.netty.channel.ChannelHandlerAdapter;import io.netty.channel.ChannelHandlerContext;import java.util.Date;public class TimeClientHandler extends ChannelHandlerAdapter {    private ByteBuf buf;    @Override    public void handlerAdded(ChannelHandlerContext ctx) {        buf = ctx.alloc().buffer(4); // (1)    }    @Override    public void handlerRemoved(ChannelHandlerContext ctx) {        buf.release(); // (1)        buf = null;    }    @Override    public void channelRead(ChannelHandlerContext ctx, Object msg) {        ByteBuf m = (ByteBuf) msg;        buf.writeBytes(m); // (2)        m.release();        if (buf.readableBytes() >= 4) { // (3)            long currentTimeMillis = (buf.readInt() - 2208988800L) * 1000L;            System.out.println(new Date(currentTimeMillis));            ctx.close();        }    }    @Override    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {        cause.printStackTrace();        ctx.close();    }}

package io.netty.example.time;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 TimeClient {    public static void main(String[] args) throws Exception {        String host = args[0];        int port = Integer.parseInt(args[1]);        EventLoopGroup workerGroup = new NioEventLoopGroup();        try {            Bootstrap b = new Bootstrap(); // (1)            b.group(workerGroup); // (2)            b.channel(NioSocketChannel.class); // (3)            b.option(ChannelOption.SO_KEEPALIVE, true); // (4)            b.handler(new ChannelInitializer<SocketChannel>() {                @Override                public void initChannel(SocketChannel ch) throws Exception {                    ch.pipeline().addLast(new TimeDecoder(), new TimeClientHandler());                }            });            // Start the client.            ChannelFuture f = b.connect(host, port).sync(); // (5)            // Wait until the connection is closed.            f.channel().closeFuture().sync();        } finally {            workerGroup.shutdownGracefully();        }    }}

程序启动后，输出结果：

也可以把TimeDecoder.java从ReplayingDecoder继承：

package io.netty.example.time;import java.util.List;import io.netty.buffer.ByteBuf;import io.netty.channel.ChannelHandlerContext;import io.netty.handler.codec.ReplayingDecoder;public class TimeDecoder extends ReplayingDecoder<Void> {    @Override    protected void decode(            ChannelHandlerContext ctx, ByteBuf in, List<Object> out) {        out.add(in.readBytes(4));    }}

运行也可以输出结果。

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