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netty echo 入门实现及启动完整介绍

netty echo 入门实现及启动完整介绍

作者: 黎明_dba5 | 来源:发表于2020-01-18 10:47 被阅读0次

    说明

    避免走弯路，查找各种资料，本文提供完整的NettyServer及NettyClient的完整实现，及启动，方便其他初学者参考，不对代码本身做解说。

    NettyServer

    新建一个maven空白项目，项目名NettyServer

    根pom.xml文件中加入netty依赖

    <dependencies>
       <!-- https://mvnrepository.com/artifact/io.netty/netty-all -->
       <dependency>
           <groupId>io.netty</groupId>
           <artifactId>netty-all</artifactId>
           <version>4.1.44.Final</version>
       </dependency>
   </dependencies>
    创建EchoServerHandler，具体实现
    import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.*;
import io.netty.util.CharsetUtil;

/**
 * 
 */
//标示一个ChannelHandler可以被多个channel安全的共享
@ChannelHandler.Sharable
public class EchoServerHandler extends ChannelInboundHandlerAdapter{
    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        ByteBuf in =(ByteBuf)msg;
        //将消息记录到控制台
        System.out.println("Server received:" + in.toString(CharsetUtil.UTF_8));
        //将接受到的消息写给发送者，而不冲刷出站消息
        ctx.write(in);
    }

    @Override
    public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
        //将未决消息冲刷到远程节点，并且关闭改Channel
        ctx.writeAndFlush(Unpooled.EMPTY_BUFFER).addListener(ChannelFutureListener.CLOSE);
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        //打印异常栈信息
        cause.printStackTrace();
        //关闭该Channel
        ctx.close();
    }
}
    创建启动引导类
    import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
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 java.net.InetSocketAddress;

/**
 *
 */
public class EchoServer {
    private final int port;
    public EchoServer(int port){
        this.port = port;
    }

    public static void main(String[] args) throws Exception {
        if (args.length != 1){
            System.err.println("Usage:" + EchoServer.class.getSimpleName() + "<port>");
        }
        int port = Integer.parseInt(args[0]);
        System.out.println(port);
        new EchoServer(port).start();
    }

    public void start() throws Exception{
        final EchoServerHandler serverHandler = new EchoServerHandler();
        EventLoopGroup group = new NioEventLoopGroup();
        try {
            ServerBootstrap bootstrap = new ServerBootstrap();
            bootstrap.group(group)
                    .channel(NioServerSocketChannel.class)
                    .localAddress(new InetSocketAddress(port))
                    //添加一个EchoServerHandler到子Channel的ChannelPipeline
                    .childHandler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel socketChannel) throws Exception {
                            socketChannel.pipeline().addLast(serverHandler);
                        }
                    });
            //异步的绑定服务器，调用sync()方法阻塞等待直到绑定完成
            ChannelFuture channelFuture = bootstrap.bind().sync();
            //获取Channel的CloseFuture，并且阻塞当前线程知道它完成
            channelFuture.channel().closeFuture().sync();
        }finally {
            //关闭EventLoopGroup,释放所有的资源
            group.shutdownGracefully().sync();
        }
    }
}
    项目配置

    pom.xml文件加入maven插件

    <build>
        <plugins>
            <plugin>
                <groupId>org.codehaus.mojo</groupId>
                <artifactId>exec-maven-plugin</artifactId>
                <version>1.6.0</version>
                <executions>
                    <execution>
                        <goals>
                            <goal>java</goal>
                        </goals>
                    </execution>
                </executions>
                <configuration>
                    <!-- main方法的入口类及参数 -->
                    <mainClass>EchoServer</mainClass>
                    <arguments>
                        <argument>8080</argument>
                    </arguments>
                </configuration>
            </plugin>
        </plugins>
    </build>

    至此，NettyServer项目已经创建完成，接下来创建NettyClient客户端

    NettyClient

    创建一个空白maven项目，项目名NettyClient

    根pom.xml文件中加入netty依赖

    <dependencies>
       <!-- https://mvnrepository.com/artifact/io.netty/netty-all -->
       <dependency>
           <groupId>io.netty</groupId>
           <artifactId>netty-all</artifactId>
           <version>4.1.44.Final</version>
       </dependency>
   </dependencies>
    EchoClientHandler
    import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandler;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.util.CharsetUtil;

/**
 * Created  on 2020/1/16.
 */
//标记改类的实例可以被多个Channel共享
@ChannelHandler.Sharable
public class EchoClientHandler extends SimpleChannelInboundHandler<ByteBuf> {

    //当被通知Channel是活跃的时候，发送一条消息
    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        ctx.writeAndFlush(Unpooled.copiedBuffer("Netty rocks!", CharsetUtil.UTF_8));
    }

    //记录已接受消息的转储
    @Override
    protected void channelRead0(ChannelHandlerContext channelHandlerContext, ByteBuf byteBuf) throws Exception {
        System.out.println("Client received:" + byteBuf.toString(CharsetUtil.UTF_8));
    }

    //在发生异常时，记录错误并关闭Channel
    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        cause.printStackTrace();
        ctx.close();
    }
}
    EchoClient
    import io.netty.bootstrap.Bootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
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 java.net.InetSocketAddress;

/**
 * Created by lunfu.chen on 2020/1/16.
 */
public class EchoClient {
    private final String host;
    private final int port;

    public EchoClient(String host, int port) {
        this.host = host;
        this.port = port;
    }

    public static void main(String[] args) throws Exception {
        System.out.println(">>>>>>>args:"+args[0]+","+args[1]);
        if (args.length != 2) {
            System.err.println("Usage:" + EchoClient.class.getSimpleName() + "<host> <port>");
            return;
        }
        String host = args[0];
        int port = Integer.parseInt(args[1]);
        new EchoClient(host, port).start();
    }

    public void start() throws Exception {
        EventLoopGroup group = new NioEventLoopGroup();
        try {
            Bootstrap b = new Bootstrap();
            b.group(group)
                    .channel(NioSocketChannel.class)
                    .remoteAddress(new InetSocketAddress(host, port))
                    .handler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel socketChannel) throws Exception {
                            socketChannel.pipeline().addLast(new EchoClientHandler());
                        }
                    });
            //连接到远程节点，阻塞等待知道连接完成
            ChannelFuture future = b.connect().sync();
            //阻塞，知道Channel关闭
            future.channel().closeFuture().sync();
        } finally {
            //关闭线程池并且释放所有的资源
            group.shutdownGracefully().sync();
        }
    }
}
    pom.xml文件中加入manve插件
    <build>
        <plugins>
            <plugin>
                <groupId>org.codehaus.mojo</groupId>
                <artifactId>exec-maven-plugin</artifactId>
                <version>1.6.0</version>
                <executions>
                    <execution>
                        <goals>
                            <goal>java</goal>
                        </goals>
                    </execution>
                </executions>
                <configuration>
                    <!-- 此处为启动类的入口及参数 -->
                    <mainClass>EchoClient</mainClass>
                    <arguments>
                        <argument>localhost</argument>
                        <argument>8080</argument>
                    </arguments>
                </configuration>
            </plugin>
        </plugins>
    </build>

    打包启动项目

    编译和启动项目我提供有两种方式，本质是一样。

    使用idea

    本人使用的编译器是idea,因此在两个项目的Terminal窗口中输入命令
    首先在NettyServer项目中操作，

    mvn clean package

    然后会有输出

    D:\workspace_lean\netty\nettyserver>mvn clean package
[INFO] Scanning for projects...
[INFO]
[INFO] ------------------------------------------------------------------------
[INFO] Building nettyserver 1.0-SNAPSHOT
[INFO] ------------------------------------------------------------------------
[INFO]
[INFO] --- maven-clean-plugin:2.5:clean (default-clean) @ nettyserver ---
[INFO] Deleting D:\workspace_lean\netty\nettyserver\target
[INFO]
[INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ nettyserver ---
[WARNING] Using platform encoding (GBK actually) to copy filtered resources, i.e. build is platform dependent!
[INFO] Copying 0 resource
[INFO]
[INFO] --- maven-compiler-plugin:3.1:compile (default-compile) @ nettyserver ---
[INFO] Changes detected - recompiling the module!
[WARNING] File encoding has not been set, using platform encoding GBK, i.e. build is platform dependent!
[INFO] Compiling 2 source files to D:\workspace_lean\netty\nettyserver\target\classes
[WARNING] /D:/workspace_lean/netty/nettyserver/src/main/java/EchoServerHandler.java:[9,7] 编码GBK的不可映射字符
[WARNING] /D:/workspace_lean/netty/nettyserver/src/main/java/EchoServerHandler.java:[9,44] 编码GBK的不可映射字符
[WARNING] /D:/workspace_lean/netty/nettyserver/src/main/java/EchoServerHandler.java:[15,24] 编码GBK的不可映射字符
[WARNING] /D:/workspace_lean/netty/nettyserver/src/main/java/EchoServerHandler.java:[17,28] 编码GBK的不可映射字符
[WARNING] /D:/workspace_lean/netty/nettyserver/src/main/java/EchoServerHandler.java:[29,21] 编码GBK的不可映射字符
[WARNING] /D:/workspace_lean/netty/nettyserver/src/main/java/EchoServer.java:[37,27] 编码GBK的不可映射字符
[WARNING] /D:/workspace_lean/netty/nettyserver/src/main/java/EchoServer.java:[49,37] 编码GBK的不可映射字符
[INFO]
[INFO] --- maven-resources-plugin:2.6:testResources (default-testResources) @ nettyserver ---
[WARNING] Using platform encoding (GBK actually) to copy filtered resources, i.e. build is platform dependent!
[INFO] skip non existing resourceDirectory D:\workspace_lean\netty\nettyserver\src\test\resources
[INFO]
[INFO] --- maven-compiler-plugin:3.1:testCompile (default-testCompile) @ nettyserver ---
[INFO] Nothing to compile - all classes are up to date
[INFO]
[INFO] --- maven-surefire-plugin:2.12.4:test (default-test) @ nettyserver ---
[INFO] No tests to run.
[INFO]
[INFO] --- maven-jar-plugin:2.4:jar (default-jar) @ nettyserver ---
[INFO] Building jar: D:\workspace_lean\netty\nettyserver\target\nettyserver-1.0-SNAPSHOT.jar
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 2.099 s
[INFO] Finished at: 2020-01-18T10:26:24+08:00
[INFO] Final Memory: 18M/215M
[INFO] ------------------------------------------------------------------------

    编译打包成功，然后在Terminal窗口中输入启动命令

    mvn exec:java

    随即控制台输出响应信息

    D:\workspace_lean\netty\nettyserver>mvn exec:java
[INFO] Scanning for projects...
[INFO]
[INFO] ------------------------------------------------------------------------
[INFO] Building nettyserver 1.0-SNAPSHOT
[INFO] ------------------------------------------------------------------------
[INFO]
[INFO] --- exec-maven-plugin:1.6.0:java (default-cli) @ nettyserver ---
8080

    接着在NettyClient项目中执行上面两个相同的命令，最后在NettyServe项目控制台会输出

    Server received:Netty rocks!

    在NettyClient项目控制台会输出,并且NettyClient项目随即关闭

    D:\workspace_lean\netty\nettyclient>mvn exec:java
[INFO] Scanning for projects...
[INFO]
[INFO] ------------------------------------------------------------------------
[INFO] Building nettyclient 1.0-SNAPSHOT
[INFO] ------------------------------------------------------------------------
[INFO]
[INFO] --- exec-maven-plugin:1.6.0:java (default-cli) @ nettyclient ---
>>>>>>>args:localhost,8080
Client received:Netty rocks!
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 6.536 s
[INFO] Finished at: 2020-01-18T10:32:07+08:00
[INFO] Final Memory: 8M/190M
[INFO] -------------------------------

    到此，idea实现Netty Echo应用程序已实现完毕，接着介绍使用windows系统命令窗口编译和启动这一功能。

    使用CMD命令窗口

    打开命令窗口，进入各自的项目文件处，eg


    image.png

    项目路径为


    image.png

    进入项目位置后，依次执行mvn clean package和mvn exec:java

    image.png image.png

    到此步，NettyServer已经启动成功，同样的方式启动NettyClient,

    并且可以使用命令窗口启动多个client客户端

    可以使用Ctrl+C关闭客户端，或者简单粗暴直接关闭idea或者命令窗口，使用命令关闭窗口方式示列


    image.png

    第一款Netty应用程序实现及启动介绍完毕！

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