netty 4.1.45 第一个netty程序

偏执的太偏执、 2023-07-04 04:56 55阅读 0赞

### 文章目录 ###

*  概述
 *  maven依赖
 *  服务端
 *  客户端
 *  运行结果

> **注：更多netty相关文章请访问博主专栏： [netty专栏][netty]**

# 概述 #

本系列文章介绍netty的学习。使用的版本是4.1.45  
jdk采用Java11

本系列文章由浅入深，先学习使用，再研究其实现原理。  
本节编写一个最简单的netty服务器。

# maven依赖 #

<dependency>
        <groupId>io.netty</groupId>
        <artifactId>netty-all</artifactId>
        <version>4.1.45.Final</version>
    </dependency>

# 服务端 #

package com.example;
    
    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;
    
    public class MyNettyServer { 
        public static void main(String[] args) { 
            //配置服务端NIO线程组
            EventLoopGroup bossGroup = new NioEventLoopGroup();
            EventLoopGroup workGroup = new NioEventLoopGroup();
    
            try { 
                ServerBootstrap serverBootstrap = new ServerBootstrap();
                serverBootstrap.group(bossGroup, workGroup)//配置主从线程组
                        .channel(NioServerSocketChannel.class)
                        .option(ChannelOption.SO_BACKLOG, 1024)//配置一些TCP的参数
                        .childHandler(new MyChildHandler());//添加自定义的channel
                //绑定8080端口
                ChannelFuture channelFuture = serverBootstrap.bind(8080).sync();
                //服务端监听端口关闭
                ChannelFuture future = channelFuture.channel().closeFuture().sync();
            } catch (Exception e) { 
                e.printStackTrace();
            } finally { 
                //netty优雅停机
                bossGroup.shutdownGracefully();
                workGroup.shutdownGracefully();
            }
        }
    }
    
    class MyChildHandler extends ChannelInitializer<SocketChannel> { 
        @Override
        protected void initChannel(SocketChannel socketChannel) { 
            //将自定义的channelhandler添加到channelpipeline的末尾
            socketChannel.pipeline().addLast(new TimeServerHandler());
        }
    }
    
    /** * TimeServerHandler这个才是服务端真正处理请求的服务方法 */
    class TimeServerHandler extends ChannelInboundHandlerAdapter { 
    
        @Override
        public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception { 
    
            //将请求入参转为ByteBuf对象
            ByteBuf byteBuf = (ByteBuf) msg;
            byte[] bytes = new byte[byteBuf.readableBytes()];
            byteBuf.readBytes(bytes);
            //由于我们这里传的参数是string，所以直接强制转换
            String body = new String(bytes, "UTF-8");
            System.out.println("收到客户端请求：" + body);
    
            SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
            String currentTimeStr = "QUERY TIME ORDER".equalsIgnoreCase(body) ?
                    format.format(new Date()) + "" : "BAD ORDER";
            ByteBuf resp = Unpooled.copiedBuffer(currentTimeStr.getBytes());
            ctx.write(resp);
        }
    
        @Override
        public void channelReadComplete(ChannelHandlerContext ctx) { 
            ctx.flush();
        }
    
        @Override
        public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) { 
            ctx.close();
        }
    }

这里配置了NIO服务端，采用的是主从线程模型，关于主从模型后续再介绍。  
服务端端口是8080.  
服务端真正处理客户端请求的方法是`com.example.TimeServerHandler#channelRead`,该方法的作用是`接收请求，返回服务器时间`。

# 客户端 #

package com.example;
    
    import io.netty.bootstrap.Bootstrap;
    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.NioSocketChannel;
    
    
    public class MyNettyClient { 
        public static void main(String[] args) { 
            //客户端NIO线程组
            EventLoopGroup group = new NioEventLoopGroup();
    
            try { 
                Bootstrap bootstrap = new Bootstrap();
                bootstrap.group(group)
                        .channel(NioSocketChannel.class)
                        .handler(new ChannelInitializer<SocketChannel>() { 
                            @Override
                            protected void initChannel(SocketChannel ch) { 
                                ch.pipeline().addLast(new TimeClientHandler());
                            }
                        });
    
                //异步链接服务器
                ChannelFuture future = bootstrap.connect("127.0.0.1", 8080).sync();
                //等等客户端链接关闭
                future.channel().closeFuture().sync();
            } catch (Exception e) { 
                e.printStackTrace();
            } finally { 
                //优雅停机
                group.shutdownGracefully();
            }
        }
    }
    
    //客户端业务逻辑处理类
    class TimeClientHandler extends ChannelInboundHandlerAdapter { 
    
        /** * 客户端与服务器TCP链路链接成功后调用该方法 * @param ctx */
        @Override
        public void channelActive(ChannelHandlerContext ctx) { 
            byte[] req = "QUERY TIME ORDER".getBytes();
            ByteBuf firstMsg = Unpooled.buffer(req.length);
            firstMsg.writeBytes(req);
            ctx.writeAndFlush(firstMsg);//写入缓冲并且发送到socketchannel
        }
    
        /** * 读取到服务端相应后执行该方法 * @param ctx * @param msg * @throws Exception */
        @Override
        public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception { 
            ByteBuf byteBuf = (ByteBuf) msg;
            byte[] bytes = new byte[byteBuf.readableBytes()];
            byteBuf.readBytes(bytes);
            String body = new String(bytes, "UTF-8");
            System.out.println("服务端返回："+body);
        }
    
        @Override
        public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception { 
            System.out.println("Unexpected exception from downstream : " + cause.getMessage());
            ctx.close();
        }
    }

# 运行结果 #

先启动服务器端，再启动客户端。可以看到客户端运行结果：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2ZneWlidXBp_size_16_color_FFFFFF_t_70]

OK，第一个netty程序就完成了，上面代码中有一些注释帮助理解运行过程。后续会再写更深入的文章。

> **注：更多netty相关文章请访问博主专栏： [netty专栏][netty]**

[netty]: https://blog.csdn.net/fgyibupi/category_9705823.html
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2ZneWlidXBp_size_16_color_FFFFFF_t_70]: https://img-blog.csdnimg.cn/20200208155243129.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2ZneWlidXBp,size_16,color_FFFFFF,t_70