编译和运行 Echo 服务器和客户端 | Essential Netty in Action 《Netty 实战(精髓)》

### 编译 *本例涉及到多模块 Maven 项目的组织* 在例子 chapter2 目录下，执行 ~~~ mvn clean package ~~~ 输出如下 Listing 2.6 Build Output ~~~ chapter2>mvn clean package [INFO] Scanning for projects... [INFO] -------------------------------------------------------------------- [INFO] Reactor Build Order: [INFO] [INFO] Echo Client and Server [INFO] Echo Client [INFO] Echo Server [INFO] [INFO] -------------------------------------------------------------------- [INFO] Building Echo Client and Server 1.0-SNAPSHOT [INFO] -------------------------------------------------------------------- [INFO] [INFO] --- maven-clean-plugin:2.5:clean (default-clean) @ echo-parent --- [INFO] [INFO] -------------------------------------------------------------------- [INFO] Building Echo Client 1.0-SNAPSHOT [INFO] -------------------------------------------------------------------- [INFO] [INFO] --- maven-clean-plugin:2.5:clean (default-clean) @ echo-client --- [INFO] [INFO] --- maven-compiler-plugin:3.1:compile (default-compile) @ echo-client --- [INFO] Changes detected - recompiling the module! [INFO] -------------------------------------------------------------------- [INFO] Reactor Summary: [INFO] [INFO] Echo Client and Server ......................... SUCCESS [ 0.118 s] [INFO] Echo Client .................................... SUCCESS [ 1.219 s] [INFO] Echo Server .................................... SUCCESS [ 0.110 s] [INFO] -------------------------------------------------------------------- [INFO] BUILD SUCCESS [INFO] -------------------------------------------------------------------- [INFO] Total time: 1.561 s [INFO] Finished at: 2014-06-08T17:39:15-05:00 [INFO] Final Memory: 14M/245M [INFO] -------------------------------------------------------------------- ~~~ 注意事项： * Maven Reactor 构建顺序：先是父 POM，然后是子项目 * Netty artifact 没在用户的本地存储库中找到，所以 Maven 就会从互联网上下载 * clean 和 compile 在构建生命周期的运行。事后 mavensurefire-plugin 插件运行，但不会有测试类存在。最后 mavenjar-plugin 执行这段说明了项目已经成功编译。 ### [](https://github.com/waylau/essential-netty-in-action/blob/master/GETTING%20STARTED/Building%20and%20running%20the%20Echo%20Server%20and%20Client.md#运行-echo-服务器-和-客户端)运行 Echo 服务器和客户端我们使用 exec-maven-plugin 来运行项目。在 chapter2/Server 目录，执行 ~~~ mvn exec:java ~~~ 输出如下： ~~~ [INFO] Scanning for projects... [INFO] [INFO] -------------------------------------------------------------------- [INFO] Building Echo Server 1.0-SNAPSHOT [INFO] -------------------------------------------------------------------- [INFO] [INFO] >>> exec-maven-plugin:1.2.1:java (default-cli) @ echo-server >>> [INFO] [INFO] <<< exec-maven-plugin:1.2.1:java (default-cli) @ echo-server <<< [INFO] [INFO] --- exec-maven-plugin:1.2.1:java (default-cli) @ echo-server --- nettyinaction.echo.EchoServer started and listening for connections on /0:0:0:0:0:0:0:0:9999 ~~~ 在 chapter2/Client 目录，执行 ~~~ mvn exec:java ~~~ 输出如下： ~~~ [INFO] Scanning for projects... [INFO] [INFO] -------------------------------------------------------------------- [INFO] Building Echo Client 1.0-SNAPSHOT [INFO] -------------------------------------------------------------------- [INFO] [INFO] >>> exec-maven-plugin:1.2.1:java (default-cli) @ echo-client >>> [INFO] [INFO] <<< exec-maven-plugin:1.2.1:java (default-cli) @ echo-client <<< [INFO] [INFO] --- exec-maven-plugin:1.2.1:java (default-cli) @ echo-client --- Client received: Netty rocks! [INFO] -------------------------------------------------------------------- [INFO] BUILD SUCCESS [INFO] -------------------------------------------------------------------- [INFO] Total time: 3.907 s [INFO] Finished at: 2014-06-08T18:26:14-05:00 [INFO] Final Memory: 8M/245M [INFO] -------------------------------------------------------------------- ~~~ 在服务器的控制台输出： ~~~ Server received: Netty rocks! ~~~ 发生了什么事： * 客户端连接后，它发送消息：“Netty rocks！” * 服务器输出接收到消息并将其返回给客户端 * 客户输出接收到的消息并退出。每次运行客户端，你会看到在服务器的控制台输出： ~~~ Server received: Netty rocks! ~~~ 现在，我们看下错误的情况。在控制台输入 Ctrl-C 来关闭服务器。而后运行客户端，此时输出如下： ~~~ [INFO] Scanning for projects... [INFO] [INFO] -------------------------------------------------------------------- [INFO] Building Echo Client 1.0-SNAPSHOT [INFO] -------------------------------------------------------------------- [INFO] [INFO] >>> exec-maven-plugin:1.2.1:java (default-cli) @ echo-client >>> [INFO] [INFO] <<< exec-maven-plugin:1.2.1:java (default-cli) @ echo-client <<< [INFO] [INFO] --- exec-maven-plugin:1.2.1:java (default-cli) @ echo-client --- [WARNING] java.lang.reflect.InvocationTargetException at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke (NativeMethodAccessorImpl.java:57) at sun.reflect.DelegatingMethodAccessorImpl.invoke (DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:606) at org.codehaus.mojo.exec.ExecJavaMojo$1.run(ExecJavaMojo.java:297) at java.lang.Thread.run(Thread.java:744) Caused by: java.net.ConnectException: Connection refused: no further information: localhost/127.0.0.1:9999 at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method) at sun.nio.ch.SocketChannelImpl.finishConnect (SocketChannelImpl.java:739) at io.netty.channel.socket.nio.NioSocketChannel .doFinishConnect(NioSocketChannel.java:191) at io.netty.channel.nio. AbstractNioChannel$AbstractNioUnsafe.finishConnect( AbstractNioChannel.java:279) at io.netty.channel.nio.NioEventLoop .processSelectedKey(NioEventLoop.java:511) at io.netty.channel.nio.NioEventLoop .processSelectedKeysOptimized(NioEventLoop.java:461) at io.netty.channel.nio.NioEventLoop .processSelectedKeys(NioEventLoop.java:378) at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:350) at io.netty.util.concurrent .SingleThreadEventExecutor$2.run (SingleThreadEventExecutor.java:101) ... 1 more [INFO] -------------------------------------------------------------------- [INFO] BUILD FAILURE [INFO] -------------------------------------------------------------------- [INFO] Total time: 3.728 s [INFO] Finished at: 2014-06-08T18:49:13-05:00 [INFO] Final Memory: 8M/245M [INFO] -------------------------------------------------------------------- [ERROR] Failed to execute goal org.codehaus.mojo:exec-maven-plugin:1.2.1:java (default-cli) on project echo-client: An exception occured while executing the Java class. null: InvocationTargetException: Connection refused: no further information: localhost/127.0.0.1:9999 -> [Help 1] ~~~ 发生了啥？客户端尝试连接服务器，但服务器是关闭的，所以引发了一个 java.net.ConnectException ，这个异常被 EchoClientHandler 的 exceptionCaught() 触发，打印出异常信息，并关闭 channel