DelimiterBasedFrameDecoder案例

DelimiterBasedFrameDecoder案例教程

上一章，我们了解了 DelimiterBasedFrameDecoder 理论知识，它在 Netty 中是一个特殊字符码解码器，有着很重要的作用。它会找接收到的消息里面是否有自定义的特殊字符 。如果有就认为这个标识之前的数据就是一段数据。

案例

我们新建一个 Maven 项目，然后在根 pom 文件中引入 Netty 相关 jar 包。代码如下：

 <dependencies>
        <dependency>
            <groupId>io.netty</groupId>
            <artifactId>netty-all</artifactId>
            <version>4.1.20.Final</version>
        </dependency>
    </dependencies>

Server端

DelimiterBasedFrameServer

package net.haicoder.delimiterBasedFrameDecoder;
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.string.StringDecoder;
import io.netty.handler.logging.LogLevel;
import io.netty.handler.logging.LoggingHandler;
public class DelimiterBasedFrameServer {
    public void bind(int port) throws Exception {
        EventLoopGroup bossGroup = new NioEventLoopGroup();
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            ServerBootstrap b = new ServerBootstrap();
            b.group(bossGroup, workerGroup)
                    .channel(NioServerSocketChannel.class)
                    .option(ChannelOption.SO_BACKLOG, 100)
                    .handler(new LoggingHandler(LogLevel.INFO))
                    .childHandler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel ch) throws Exception {
                            ByteBuf delimiter = Unpooled.copiedBuffer("$_".getBytes());
                            ByteBuf delimiter1 = Unpooled.copiedBuffer("*_".getBytes());
                            ch.pipeline().addLast(new DelimiterBasedFrameDecoder(1024, delimiter,delimiter1));
                            ch.pipeline().addLast(new StringDecoder());
                            ch.pipeline().addLast(new DelimiterBasedFrameServerHandler());
                        }
                    });
            ChannelFuture future = b.bind(port).sync();
            future.channel().closeFuture().sync();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }
    public static void main(String[] args) throws Exception {
        int port = 8080;
        new DelimiterBasedFrameServer().bind(port);
    }
}

DelimiterBasedFrameServerHandler

package net.haicoder.delimiterBasedFrameDecoder;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
public class DelimiterBasedFrameServerHandler extends ChannelInboundHandlerAdapter {
    int counter = 0;
    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        String body = (String) msg;
        System.out.println("This is " + ++counter + " times receive client : [ " + body + " ]");
        //客户端也需要根据这个特殊字符进行解码，所以我们在返回客户端之前也加了该特殊字符
        body += "$_";
        ByteBuf echo = Unpooled.copiedBuffer(body.getBytes());
        ctx.writeAndFlush(echo);
    }
    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
        ctx.close();
    }
}

客户端

DelimiterBasedFrameClient

package net.haicoder.delimiterBasedFrameDecoder;
import io.netty.bootstrap.Bootstrap;
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.NioSocketChannel;
import io.netty.handler.codec.DelimiterBasedFrameDecoder;
import io.netty.handler.codec.string.StringDecoder;
public class DelimiterBasedFrameClient {
    public void connect(int port, String host) throws Exception {
        EventLoopGroup group = new NioEventLoopGroup();
        try {
            Bootstrap b = new Bootstrap();
            b.group(group).channel(NioSocketChannel.class)
                    .option(ChannelOption.TCP_NODELAY, true)
                    .handler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel ch) throws Exception {
                            ByteBuf delimiter = Unpooled.copiedBuffer("$_".getBytes());
                            ch.pipeline().addLast(new DelimiterBasedFrameDecoder(1024, delimiter));
                            ch.pipeline().addLast(new StringDecoder());
                            ch.pipeline().addLast(new DelimiterBasedFrameClientHandler());
                        }
                    });
            ChannelFuture f = b.connect(host, port).sync();
            f.channel().closeFuture().sync();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            group.shutdownGracefully();
        }
    }
    public static void main(String[] args) throws Exception {
        int port = 8080;
        new DelimiterBasedFrameClient().connect(port, "127.0.0.1");
    }
}

DelimiterBasedFrameClientHandler

package net.haicoder.delimiterBasedFrameDecoder;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
public class DelimiterBasedFrameClientHandler extends ChannelInboundHandlerAdapter {
    private int counter;
    static final String ECHO_REQ = "你好，嗨客网，欢迎来到 Netty 世界。$_，哈哈，你可以成功的。";
    @Override
    public void channelActive(ChannelHandlerContext ctx) {
        for (int i = 0; i < 3; i++) {
            ctx.writeAndFlush(Unpooled.copiedBuffer(ECHO_REQ.getBytes()));
        }
    }
    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        System.out.println("This is " + ++counter + " times receive server : [" + msg + " ]");
    }
    @Override
    public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
        ctx.flush();
    }
    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
        ctx.close();
    }
}

运行结果如下：

服务端

客户端

DelimiterBasedFrameDecoder案例总结

DelimiterBasedFrameDecoder 是特殊字符解码器，它可以识别自定义的特殊字符，然后将特殊字符之间的数据进行截取。