Netty-3.md

Netty4入门基础(二)之编写http客户端与服务端

Netty中客户端、服务端的编解码器 作为服务端而言： 主要工作就是接收客户端请求，将客户端的请求内容解码；发送响应给客户端，并将发送内容编码 所以，服务端需要两个编解码器

• HttpRequestDecoder(将请求内容解码)
• HttpResponseEncoder(将响应内容编码)

作为客户端而言： 主要工作就是发送请求给服务端，并将发送内容编码；接收服务端响应，并将接收内容解码； 所以，客户端需要两个编解码器

• HttpResponseDecoder（将响应内容解码）
• HttpRequestEncoder（将请求内容编码）

这次我们可以编写服务端和客户端，将二者连接起来，实现双向的通信。

大致的套路和逻辑还和以前相似，新建下面这几个类

public class NettyServer {
    public static void main(String[] args) throws InterruptedException {
        EventLoopGroup bossGroup = new NioEventLoopGroup();
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            ServerBootstrap serverGroup = new ServerBootstrap();
            serverGroup.group(bossGroup,workerGroup).channel(NioServerSocketChannel.class)
                    .childHandler(new NettyInitializer());
            ChannelFuture channelFuture = serverGroup.bind(8899).sync();
            channelFuture.channel().closeFuture().sync();
        }finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }

    }
}

public class NettyInitializer extends ChannelInitializer<SocketChannel> {
    @Override
    protected void initChannel(SocketChannel ch) throws Exception {
        ChannelPipeline channelPipeline = ch.pipeline();
        channelPipeline.addLast(new LengthFieldBasedFrameDecoder(Integer.MAX_VALUE,0,4,0,4));
        channelPipeline.addLast(new LengthFieldPrepender(4));
        channelPipeline.addLast(new StringDecoder(CharsetUtil.UTF_8));
        channelPipeline.addLast(new StringEncoder(CharsetUtil.UTF_8));
        channelPipeline.addLast(new NettyHandler());
    }
}

public class NettyHandler extends SimpleChannelInboundHandler<String> {

    @Override
    protected void channelRead0(ChannelHandlerContext ctx, String msg) throws Exception {
        System.out.println(ctx.channel().remoteAddress()+"   "+msg);
        ctx.channel().writeAndFlush("from server "+ UUID.randomUUID());
    }
    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        ctx.writeAndFlush("from server data");
    }
    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        cause.printStackTrace();
        ctx.close();
    }
}

public class NettyClient {
    public static void main(String[] args) throws InterruptedException {
        EventLoopGroup eventLoopGroup = new NioEventLoopGroup();
        try {
            Bootstrap bootstrap = new Bootstrap();
            bootstrap.group(eventLoopGroup).channel(NioSocketChannel.class)
                    .handler(new NettyClientInitializer2());
            ChannelFuture channelFuture = bootstrap.connect("localhost",8899).sync();
            channelFuture.channel().closeFuture().sync();
        }finally {
            eventLoopGroup.shutdownGracefully();
        }
    }
}

public class NettyClientInitializer2 extends ChannelInitializer<SocketChannel> {
    @Override
    protected void initChannel(SocketChannel ch) throws Exception {
        ChannelPipeline channelPipeline = ch.pipeline();
        channelPipeline.addLast(new LengthFieldBasedFrameDecoder(Integer.MAX_VALUE,0,4,0,4));
        channelPipeline.addLast(new LengthFieldPrepender(4));
        channelPipeline.addLast(new StringDecoder(CharsetUtil.UTF_8));
        channelPipeline.addLast(new StringEncoder(CharsetUtil.UTF_8));
        channelPipeline.addLast(new NettyClientHandler());
    }
}

public class NettyClientHandler extends SimpleChannelInboundHandler<String> {
    @Override
    protected void channelRead0(ChannelHandlerContext ctx, String msg) throws Exception {
        System.out.println(ctx.channel().remoteAddress());
        System.out.println(msg);
        ctx.channel().writeAndFlush(""+System.currentTimeMillis());
//        ctx.close();
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        cause.printStackTrace();
        ctx.close();
    }
}

之后启动server和client就可以看到控制台里打印的信息了。