Java实现WebSocket

╰半橙微兮° 2022-06-06 02:24 206阅读 0赞

[java][] [Tomcat][] [websocket][]

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## Java现实WebSocket ##

[无所不能的Java系列文章][Java]，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。

[![java-websocket][]][java-websocket]

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。

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 -version
    java 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 -version
    Apache 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\jre
    Default locale: zh_CN, platform encoding: GBK
    OS name: "windows 7", version: "6.1", arch: "amd64", family: "windows"
    
    ~ D:\toolkit\tomcat7\bin>catalina.bat version
    Using 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/7.0.39
    Server built:   Mar 22 2013 12:37:24
    Server number:  7.0.39.0
    OS Name:        Windows 7
    OS Version:     6.1
    Architecture:   amd64
    JVM Version:    1.6.0_45-b06
    JVM 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

[![ws1][]][ws1]

4). 编辑pom.xml配置文件，增加tomcat的依赖

~ vi pom.xml
    <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>org.conan.websocket</groupId>
    <artifactId>websocketServer</artifactId>
    <packaging>war</packaging>
    <version>1.0-SNAPSHOT</version>
    <name>websocketServer Maven Webapp</name>
    <url>http://maven.apache.org</url>
    <dependencies>
    <dependency>
    <groupId>org.apache.tomcat</groupId>
    <artifactId>tomcat-catalina</artifactId>
    <version>7.0.27</version>
    <scope>provided</scope>
    </dependency>
    <dependency>
    <groupId>org.apache.tomcat</groupId>
    <artifactId>tomcat-coyote</artifactId>
    <version>7.0.39</version>
    <scope>provided</scope>
    </dependency>
    </dependencies>
    <build>
    <finalName>websocketServer</finalName>
    </build>
    </project>

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.java
    
    package 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
    
    <?xml version="1.0" encoding="UTF-8"?>
    <web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
    <display-name>Archetype Created Web Application</display-name>
    <servlet>
    <servlet-name>wsServlet</servlet-name>
    <servlet-class>org.conan.websocket.DemoServlet</servlet-class>
    </servlet>
    <servlet-mapping>
    <servlet-name>wsServlet</servlet-name>
    <url-pattern>/wsServlet</url-pattern>
    </servlet-mapping>
    </web-app>

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 run
    Using 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 fou
    nd 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 Fi
    les (x86)\Microsoft SQL Server\100\Tools\Binn\;C:\Program Files\Microsoft SQL Server\100\Tools\Binn\;C:\Program Files\Mi
    crosoft 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\gra
    dle15\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:\tool
    kit\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 ms
    2013-8-20 14:43:30 org.apache.catalina.core.StandardService startInternal
    信息: Starting service Catalina
    2013-8-20 14:43:30 org.apache.catalina.core.StandardEngine startInternal
    信息: Starting Servlet Engine: Apache Tomcat/7.0.39
    2013-8-20 14:43:30 org.apache.catalina.startup.HostConfig deployWAR
    信息: Deploying web application archive D:\toolkit\tomcat7\webapps\websocketServer.war
    2013-8-20 14:43:30 org.apache.catalina.startup.HostConfig deployDirectory
    信息: Deploying web application directory D:\toolkit\tomcat7\webapps\docs
    2013-8-20 14:43:30 org.apache.catalina.startup.HostConfig deployDirectory
    信息: Deploying web application directory D:\toolkit\tomcat7\webapps\examples
    2013-8-20 14:43:31 org.apache.catalina.startup.HostConfig deployDirectory
    信息: Deploying web application directory D:\toolkit\tomcat7\webapps\host-manager
    2013-8-20 14:43:31 org.apache.catalina.startup.HostConfig deployDirectory
    信息: Deploying web application directory D:\toolkit\tomcat7\webapps\manager
    2013-8-20 14:43:31 org.apache.catalina.startup.HostConfig deployDirectory
    信息: Deploying web application directory D:\toolkit\tomcat7\webapps\ROOT
    2013-8-20 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, “[JSR 365, Java API for WebSocket][JSR 365_ Java API for 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
    <dependency>
    <groupId>org.java-websocket</groupId>
    <artifactId>Java-WebSocket</artifactId>
    <version>1.3.0</version>
    </dependency>

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.java
    
    package 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  
[![ws6][]][ws6]

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”。  
[![ws4][]][ws4]

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。  
[![ws5][]][ws5]

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
    
    <!DOCTYPE html>
    <html>
    <head>
    <meta charset=UTF-8>
    <title>Tomcat WebSocket Chat</title>
    <script>
    var ws = new WebSocket("ws://localhost:8080/websocketServer/wsServlet");
    ws.onopen = function(){
    };
    ws.onmessage = function(message){
    document.getElementById("chatlog").textContent += message.data + "\n";
    };
    function postToServer(){
    ws.send(document.getElementById("msg").value);
    document.getElementById("msg").value = "";
    }
    function closeConnect(){
    ws.close();
    }
    </script>
    </head>
    <body>
    <textarea id="chatlog" readonly></textarea><br/>
    <input id="msg" type="text" />
    <button type="submit" id="sendButton" onClick="postToServer()">Send!</button>
    <button type="submit" id="sendButton" onClick="closeConnect()">End</button>
    </body>
    </html>

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

打开两个窗口：  
[![ws2][]][ws2]

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”。  
[![ws3][]][ws3]

原来在浏览器上面，实现聊天功能是如此地简单！！

转载请注明出处：

关于作者

*  张丹(Conan), 程序员Java,R,PHP,Javascript
 *  weibo：@Conan\_Z
 *  blog: [http://blog.fens.me][http_blog.fens.me]
 *  email: bsspirit@gmail.com

[http://blog.fens.me/nodejs-websocket-intro/][http_blog.fens.me_nodejs-websocket-intro]

[java]: http://blog.fens.me/tag/java/
[Tomcat]: http://blog.fens.me/tag/tomcat/
[websocket]: http://blog.fens.me/tag/websocket/
[16 Comments]: http://blog.fens.me/java-websocket-intro/#disqus_thread
[Java]: http://blog.fens.me/series-java/
[java-websocket]: /images/20220606/76d6c010fda54a0f97407ad3b25f8824.png
[ws1]: /images/20220606/7b239368945f49f399d3985a3527b03d.png
[JSR 365_ Java API for WebSocket]: http://www.oracle.com/technetwork/articles/java/jsr356-1937161.html
[ws6]: /images/20220606/005a5525ec844434944e5a6a902455c9.png
[ws4]: /images/20220606/21d685b435904a5e8e176a365c82e83f.png
[ws5]: /images/20220606/23dff160cbc14accbf79981f227ab55d.png
[ws2]: /images/20220606/eaeaf02a6f24410bb5e8314cedbc178d.png
[ws3]: /images/20220606/34fe25a7919c45c9869a32a06fff3a5e.png
[http_blog.fens.me]: http://blog.fens.me/
[http_blog.fens.me_nodejs-websocket-intro]: http://blog.fens.me/nodejs-websocket-intro/