，涵盖了Java的思想，应用开发，设计模式，程序架构等，通过我的经验去诠释Java的强大。

说起Java，真的有点不知道从何说起。Java是一门全领域发展的语言，从基础的来讲有4大块，Java语法，JDK，JVM，第三方类库。官方又以面向不同应用的角度，又把JDK分为JavaME，JavaSE，JavaEE三个部分。Java可以做客户端界面，可以做中间件，可以做手机系统，可以做应用，可以做工具，可以做游戏，可以做算法…，Java几乎无所不能。

在Java的世界里，Java就是一切。

关于作者

• 张丹(Conan), 程序员Java,R,PHP,Javascript
• weibo：@Conan_Z
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• email: bsspirit@gmail.com

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前言

伴随着HTML5技术的新起，WebSocket 作为一种浏览器与服务器的核心通信技术，被嵌入到了浏览器的内核中。WebSocket 的出现使得浏览器提供对 Socket 的支持成为可能，从而在浏览器和服务器之间提供了一个基于 TCP 连接的双向通道。

所有新的技术都会第一时间在Java社区，出现对应的开源项目！WebSocket也被实现在多种Java的开源库中。WebSocket实现列表：https://java.net/projects/websocket-spec/pages/WebSocketAPIs/text。

今天就让我们用Java来解密一下WebSocket的服务器端和客户端 实现。

目录

1. 服务器端实现(Tomcat)
2. 客户端实现(Java-WebSocket)
3. 客户端实现(Javascript原生API)

1. 服务器端实现(Tomcat)

用Java实现的websocket，在Server端是通过Tomcat内嵌支持的，我们需要开发一个继承WebSocketServlet 的servlet就可以了，与普通的HttpServlet没有太大区别。

1). JAVA环境：

• Java: jdk 1.6.0_45, Server VM 64bit
• Maven: 3.0.5
• Tomcat: 7.0.39.0

~ D:\workspace\java>java -versionjava version "1.6.0_45"Java(TM) SE Runtime Environment (build 1.6.0_45-b06)Java HotSpot(TM) 64-Bit Server VM (build 20.45-b01, mixed mode)~ D:\workspace\java>mvn -versionApache Maven 3.0.5 (r01de14724cdef164cd33c7c8c2fe155faf9602da; 2013-02-19 21:51:28+0800)Maven home: D:\toolkit\maven3\bin\..Java version: 1.6.0_45, vendor: Sun Microsystems Inc.Java home: D:\toolkit\java\jdk6\jreDefault locale: zh_CN, platform encoding: GBKOS name: "windows 7", version: "6.1", arch: "amd64", family: "windows"~ D:\toolkit\tomcat7\bin>catalina.bat versionUsing CATALINA_BASE:   "D:\toolkit\tomcat7"Using CATALINA_HOME:   "D:\toolkit\tomcat7"Using CATALINA_TMPDIR: "D:\toolkit\tomcat7\temp"Using JRE_HOME:        "D:\toolkit\java\jdk6"Using CLASSPATH:       "D:\toolkit\tomcat7\bin\bootstrap.jar;D:\toolkit\tomcat7\bin\tomcat-juli.jar"Server version: Apache Tomcat/7.0.39Server built:   Mar 22 2013 12:37:24Server number:  7.0.39.0OS Name:        Windows 7OS Version:     6.1Architecture:   amd64JVM Version:    1.6.0_45-b06JVM Vendor:     Sun Microsystems Inc.

2). maven构建一个简单的webapp项目。

~ D:\workspace\java>mvn archetype:generate -DgroupId=org.conan.websocket -DartifactId=websocketServer -DarchetypeArtifactId=maven-archetype-webapp[INFO] ----------------------------------------------------------------------------[INFO] Using following parameters for creating project from Old (1.x) Archetype: maven-archetype-webapp:1.0[INFO] ----------------------------------------------------------------------------[INFO] Parameter: groupId, Value: org.conan.websocket[INFO] Parameter: packageName, Value: org.conan.websocket[INFO] Parameter: package, Value: org.conan.websocket[INFO] Parameter: artifactId, Value: websocketServer[INFO] Parameter: basedir, Value: D:\workspace\java[INFO] Parameter: version, Value: 1.0-SNAPSHOT[INFO] project created from Old (1.x) Archetype in dir: D:\workspace\java\websocketServer[INFO] ------------------------------------------------------------------------[INFO] BUILD SUCCESS[INFO] ------------------------------------------------------------------------[INFO] Total time: 1:42.200s[INFO] Finished at: Tue Aug 20 13:57:05 CST 2013[INFO] Final Memory: 9M/179M[INFO] ------------------------------------------------------------------------

3). 配置项目目录

~ D:\workspace\java>cd websocketServer~ D:\workspace\java\websocketServer>mkdir src\main\java~ D:\workspace\java\websocketServer>rm src\main\webapp\index.jsp

导入到Eclipse的项目截图

4). 编辑pom.xml配置文件，增加tomcat的依赖

~ vi pom.xml
    
     
      4.0.0
     
     
      org.conan.websocket
     
     
      websocketServer
     
     
      war
     
     
      1.0-SNAPSHOT
     
     
      websocketServer Maven Webapp
     
     
      http://maven.apache.org
     
     
      
       
        org.apache.tomcat
       
       
        tomcat-catalina
       
       
        7.0.27
       
       
        provided
       
      
      
       
        org.apache.tomcat
       
       
        tomcat-coyote
       
       
        7.0.39
       
       
        provided
       
      
     
     
      
       websocketServer
      
     
    

下载并安装类库

~ D:\workspace\java\websocketServer>mvn clean install

5). 创建DemoServlet，服务器端运行类

~ vi src/main/java/org/conan/websocket/DemoServlet.javapackage org.conan.websocket;import java.io.IOException;import java.nio.ByteBuffer;import java.nio.CharBuffer;import java.util.ArrayList;import javax.servlet.http.HttpServletRequest;import org.apache.catalina.websocket.MessageInbound;import org.apache.catalina.websocket.StreamInbound;import org.apache.catalina.websocket.WebSocketServlet;import org.apache.catalina.websocket.WsOutbound;public class DemoServlet extends WebSocketServlet {    private static final long serialVersionUID = -4853540828121130946L;    private static ArrayList mmiList = new ArrayList();    @Override    protected StreamInbound createWebSocketInbound(String str, HttpServletRequest request) {        return new MyMessageInbound();    }    private class MyMessageInbound extends MessageInbound {        WsOutbound myoutbound;        @Override        public void onOpen(WsOutbound outbound) {            try {                System.out.println("Open Client.");                this.myoutbound = outbound;                mmiList.add(this);                outbound.writeTextMessage(CharBuffer.wrap("Hello!"));            } catch (IOException e) {                e.printStackTrace();            }        }        @Override        public void onClose(int status) {            System.out.println("Close Client.");            mmiList.remove(this);        }        @Override        public void onTextMessage(CharBuffer cb) throws IOException {            System.out.println("Accept Message : " + cb);            for (MyMessageInbound mmib : mmiList) {                CharBuffer buffer = CharBuffer.wrap(cb);                mmib.myoutbound.writeTextMessage(buffer);                mmib.myoutbound.flush();            }        }        @Override        public void onBinaryMessage(ByteBuffer bb) throws IOException {        }    }}

6). 修改web.xml文件

~ vi src/main/webapp/WEB-INF/web.xml
    
    
     
      Archetype Created Web Application
     
     
      
       wsServlet
      
      
       org.conan.websocket.DemoServlet
      
     
     
      
       wsServlet
      
      
       /wsServlet
      
     
    

7). 编译，打包，部署到tomcat

~ D:\workspace\java\websocketServer>mvn clean install~ D:\workspace\java\websocketServer>cp target\websocketServer.war D:\toolkit\tomcat7\webapps

启动tomcat

~ D:\toolkit\tomcat7>bin\catalina.bat runUsing CATALINA_BASE:   "D:\toolkit\tomcat7"Using CATALINA_HOME:   "D:\toolkit\tomcat7"Using CATALINA_TMPDIR: "D:\toolkit\tomcat7\temp"Using JRE_HOME:        "D:\toolkit\java\jdk6"Using CLASSPATH:       "D:\toolkit\tomcat7\bin\bootstrap.jar;D:\toolkit\tomcat7\bin\tomcat-juli.jar"2013-8-20 14:43:29 org.apache.catalina.core.AprLifecycleListener init信息: The APR based Apache Tomcat Native library which allows optimal performance in production environments was not found on the java.library.path: D:\toolkit\java\jdk6\bin;C:\Windows\Sun\Java\bin;C:\Windows\system32;C:\Windows;D:\toolkit\Rtools\bin;D:\toolkit\Rtools\gcc-4.6.3\bin;C:\Program Files (x86)\Common Files\NetSarang;C:\Windows\system32;C:\Windows;C:\Windows\System32\Wbem;C:\Windows\System32\WindowsPowerShell\v1.0\;D:\toolkit\Git\cmd;D:\toolkit\Git\bin;C:\Program Files (x86)\Microsoft SQL Server\100\Tools\Binn\;C:\Program Files\Microsoft SQL Server\100\Tools\Binn\;C:\Program Files\Microsoft SQL Server\100\DTS\Binn\;c:\Program Files (x86)\Common Files\Ulead Systems\MPEG;C:\Program Files (x86)\QuickTime\QTSystem\;D:\toolkit\MiKTex\miktex\bin\x64\;D:\toolkit\sshclient;D:\toolkit\ant19\bin;D:\toolkit\eclipse;D:\toolkit\gradle15\bin;D:\toolkit\java\jdk6\bin;D:\toolkit\maven3\bin;D:\toolkit\mysql56\bin;D:\toolkit\python27;D:\toolkit\putty;C:\Program Files\R\R-3.0.1\bin\x64;D:\toolkit\mongodb243\bin;D:\toolkit\php54;D:\toolkit\nginx140;D:\toolkit\nodejs;D:\toolkit\npm12\bin;D:\toolkit\java\jdk6\jre\bin\server;.2013-8-20 14:43:30 org.apache.coyote.AbstractProtocol init信息: Initializing ProtocolHandler ["http-bio-8080"]2013-8-20 14:43:30 org.apache.coyote.AbstractProtocol init信息: Initializing ProtocolHandler ["ajp-bio-8009"]2013-8-20 14:43:30 org.apache.catalina.startup.Catalina load信息: Initialization processed in 1409 ms2013-8-20 14:43:30 org.apache.catalina.core.StandardService startInternal信息: Starting service Catalina2013-8-20 14:43:30 org.apache.catalina.core.StandardEngine startInternal信息: Starting Servlet Engine: Apache Tomcat/7.0.392013-8-20 14:43:30 org.apache.catalina.startup.HostConfig deployWAR信息: Deploying web application archive D:\toolkit\tomcat7\webapps\websocketServer.war2013-8-20 14:43:30 org.apache.catalina.startup.HostConfig deployDirectory信息: Deploying web application directory D:\toolkit\tomcat7\webapps\docs2013-8-20 14:43:30 org.apache.catalina.startup.HostConfig deployDirectory信息: Deploying web application directory D:\toolkit\tomcat7\webapps\examples2013-8-20 14:43:31 org.apache.catalina.startup.HostConfig deployDirectory信息: Deploying web application directory D:\toolkit\tomcat7\webapps\host-manager2013-8-20 14:43:31 org.apache.catalina.startup.HostConfig deployDirectory信息: Deploying web application directory D:\toolkit\tomcat7\webapps\manager2013-8-20 14:43:31 org.apache.catalina.startup.HostConfig deployDirectory信息: Deploying web application directory D:\toolkit\tomcat7\webapps\ROOT2013-8-20 14:43:31 org.apache.coyote.AbstractProtocol start信息: Starting ProtocolHandler ["http-bio-8080"]2013-8-20 14:43:31 org.apache.coyote.AbstractProtocol start信息: Starting ProtocolHandler ["ajp-bio-8009"]2013-8-20 14:43:31 org.apache.catalina.startup.Catalina start信息: Server startup in 996 ms

websocket的服务地址：

ws://localhost:8080/websocketServer/wsServlet

2. 客户端实现(Java-WebSocket)

通过Java实现websocket的客户端，这里将介绍的是”Java-WebSocket”。另外，我发现Java7已经原生支持了websocket, “” (看来要开始学学java7和java8了，我在java6的时代停滞3-4年了。)

现在我们使用“Java-WebSocket”

1). 修改pom.xml文件，增加jetty websocket依赖库

~ vi pom.xml
    
     
      org.java-websocket
     
     
      Java-WebSocket
     
     
      1.3.0
     
    

下载依赖库

~ D:\workspace\java\websocketServer>mvn clean install

2). 新建文件，ChatClient.java

~ vi src/main/java/org/conan/websocket/ChatClient.javapackage org.conan.websocket;import java.awt.Container;import java.awt.GridLayout;import java.awt.event.ActionEvent;import java.awt.event.ActionListener;import java.awt.event.WindowEvent;import java.net.URI;import java.net.URISyntaxException;import javax.swing.JButton;import javax.swing.JComboBox;import javax.swing.JFrame;import javax.swing.JScrollPane;import javax.swing.JTextArea;import javax.swing.JTextField;import org.java_websocket.WebSocketImpl;import org.java_websocket.client.WebSocketClient;import org.java_websocket.drafts.Draft;import org.java_websocket.drafts.Draft_10;import org.java_websocket.drafts.Draft_17;import org.java_websocket.drafts.Draft_75;import org.java_websocket.drafts.Draft_76;import org.java_websocket.handshake.ServerHandshake;public class ChatClient extends JFrame implements ActionListener {    private static final long serialVersionUID = -6056260699202978657L;    private final JTextField uriField;    private final JButton connect;    private final JButton close;    private final JTextArea ta;    private final JTextField chatField;    private final JComboBox draft;    private WebSocketClient cc;    public ChatClient( String defaultlocation ) {        super( "WebSocket Chat Client" );        Container c = getContentPane();        GridLayout layout = new GridLayout();        layout.setColumns( 1 );        layout.setRows( 6 );        c.setLayout( layout );        Draft[] drafts = { new Draft_17(), new Draft_10(), new Draft_76(), new Draft_75() };        draft = new JComboBox( drafts );        c.add( draft );        uriField = new JTextField();        uriField.setText( defaultlocation );        c.add( uriField );        connect = new JButton( "Connect" );        connect.addActionListener( this );        c.add( connect );        close = new JButton( "Close" );        close.addActionListener( this );        close.setEnabled( false );        c.add( close );        JScrollPane scroll = new JScrollPane();        ta = new JTextArea();        scroll.setViewportView( ta );        c.add( scroll );        chatField = new JTextField();        chatField.setText( "" );        chatField.addActionListener( this );        c.add( chatField );        java.awt.Dimension d = new java.awt.Dimension( 300, 400 );        setPreferredSize( d );        setSize( d );        addWindowListener( new java.awt.event.WindowAdapter() {            @Override            public void windowClosing( WindowEvent e ) {                if( cc != null ) {                    cc.close();                }                dispose();            }        } );        setLocationRelativeTo( null );        setVisible( true );    }    public void actionPerformed( ActionEvent e ) {        if( e.getSource() == chatField ) {            if( cc != null ) {                cc.send( chatField.getText() );                chatField.setText( "" );                chatField.requestFocus();            }        } else if( e.getSource() == connect ) {            try {                // cc = new ChatClient(new URI(uriField.getText()), area, ( Draft ) draft.getSelectedItem() );                cc = new WebSocketClient( new URI( uriField.getText() ), (Draft) draft.getSelectedItem() ) {                    @Override                    public void onMessage( String message ) {                        ta.append( "got: " + message + "\n" );                        ta.setCaretPosition( ta.getDocument().getLength() );                    }                    @Override                    public void onOpen( ServerHandshake handshake ) {                        ta.append( "You are connected to ChatServer: " + getURI() + "\n" );                        ta.setCaretPosition( ta.getDocument().getLength() );                    }                    @Override                    public void onClose( int code, String reason, boolean remote ) {                        ta.append( "You have been disconnected from: " + getURI() + "; Code: " + code + " " + reason + "\n" );                        ta.setCaretPosition( ta.getDocument().getLength() );                        connect.setEnabled( true );                        uriField.setEditable( true );                        draft.setEditable( true );                        close.setEnabled( false );                    }                    @Override                    public void onError( Exception ex ) {                        ta.append( "Exception occured ...\n" + ex + "\n" );                        ta.setCaretPosition( ta.getDocument().getLength() );                        ex.printStackTrace();                        connect.setEnabled( true );                        uriField.setEditable( true );                        draft.setEditable( true );                        close.setEnabled( false );                    }                };                close.setEnabled( true );                connect.setEnabled( false );                uriField.setEditable( false );                draft.setEditable( false );                cc.connect();            } catch ( URISyntaxException ex ) {                ta.append( uriField.getText() + " is not a valid WebSocket URI\n" );            }        } else if( e.getSource() == close ) {            cc.close();        }    }    public static void main( String[] args ) {        WebSocketImpl.DEBUG = true;        String location;        if( args.length != 0 ) {            location = args[ 0 ];            System.out.println( "Default server url specified: \'" + location + "\'" );        } else {            location = "ws://localhost:8887";            System.out.println( "Default server url not specified: defaulting to \'" + location + "\'" );        }        new ChatClient( location );    }}

运行程序：

这里会启动一个Java的GUI界面。输入websocket服务的地址：ws://localhost:8080/websocketServer/wsServlet

查看Java客户端和HTML客户端的对话，在Java客户端中，输入”你好，小朋友”。

我们发现在html的客户端中，同样出现的”你好，小朋友”的消息记录。

这样，我们就在Java6的环境中，实现了Java WebSocket的客户端程序。

3. 客户端实现(Javascript原生API)

编写一个纯HTML的网页，通过浏览器原生的websocketAPI实现对websocket的服务的调用。

~ vi D:\workspace\javascript\tomcatClient.html
    
Send!End

通过浏览器刚刚编写的文件：file:///D:/workspace/javascript/tomcatClient.html

打开两个窗口：

在右边窗口输入”我是BBB”，然后点击send。左边，右这，和后台日志，同时增加了”我是BBB”。

原来在浏览器上面，实现聊天功能是如此地简单！！

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