編譯和運行 Echo 服務器和客戶端 · Essential Netty in Action 《Netty 實戰(精髓)》

### 編譯 *本例涉及到多模塊 Maven 項目的組織* 在例子 chapter2 目錄下，執行 ~~~ mvn clean package ~~~ 輸出如下 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] -------------------------------------------------------------------- ~~~ 注意事項： * Maven Reactor 構建順序：先是父 POM，然后是子項目 * Netty artifact 沒在用戶的本地存儲庫中找到，所以 Maven 就會從互聯網上下載 * clean 和 compile 在構建生命周期的運行。事后 mavensurefire-plugin 插件運行，但不會有測試類存在。最后 mavenjar-plugin 執行這段說明了項目已經成功編譯。 ### [](https://github.com/waylau/essential-netty-in-action/blob/master/GETTING%20STARTED/Building%20and%20running%20the%20Echo%20Server%20and%20Client.md#運行-echo-服務器-和-客戶端)運行 Echo 服務器和客戶端我們使用 exec-maven-plugin 來運行項目。在 chapter2/Server 目錄，執行 ~~~ mvn exec:java ~~~ 輸出如下： ~~~ [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 目錄，執行 ~~~ mvn exec:java ~~~ 輸出如下： ~~~ [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] -------------------------------------------------------------------- ~~~ 在服務器的控制臺輸出： ~~~ Server received: Netty rocks! ~~~ 發生了什么事： * 客戶端連接后，它發送消息：“Netty rocks！” * 服務器輸出接收到消息并將其返回給客戶端 * 客戶輸出接收到的消息并退出。每次運行客戶端，你會看到在服務器的控制臺輸出： ~~~ Server received: Netty rocks! ~~~ 現在，我們看下錯誤的情況。在控制臺輸入 Ctrl-C 來關閉服務器。而后運行客戶端，此時輸出如下： ~~~ [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] ~~~ 發生了啥？客戶端嘗試連接服務器，但服務器是關閉的，所以引發了一個 java.net.ConnectException ，這個異常被 EchoClientHandler 的 exceptionCaught() 觸發，打印出異常信息，并關閉 channel