Spring WebSocket實現消息推送

第一步： 添加Spring WebSocket的依賴jar包

（注：這里使用maven方式添加 手動添加的同學請自行下載相應jar包放到lib目錄）

<!-- 使用spring websocket依賴的jar包 -->
<dependency>
     <groupId>org.springframework</groupId>
     <artifactId>spring-websocket</artifactId>
     <version>${spring.version}</version>
</dependency>
<dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-messaging</artifactId>
      <version>${spring.version}</version>
</dependency>

第二步：建立一個類實現WebSocketConfigurer接口

package com.example.demo.config;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.EnableWebMvc;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;
import org.springframework.web.socket.config.annotation.EnableWebSocket;
import org.springframework.web.socket.config.annotation.WebSocketConfigurer;
import org.springframework.web.socket.config.annotation.WebSocketHandlerRegistry;
import org.springframework.web.socket.handler.TextWebSocketHandler;

@Configuration
@EnableWebMvc
@EnableWebSocket
public class SpringWebSocketConfig extends WebMvcConfigurerAdapter implements WebSocketConfigurer {

    public void registerWebSocketHandlers(WebSocketHandlerRegistry registry) {

        //springwebsocket 4.1.5版本前默認支持跨域訪問，之后的版本默認不支持跨域，需要設置.setAllowedOrigins("*")
        registry.addHandler(webSocketHandler(),"/websocket/socketServer.do")
                .addInterceptors(new SpringWebSocketHandlerInterceptor());

        registry.addHandler(webSocketHandler(), "/sockjs/socketServer.do")
                .addInterceptors(new SpringWebSocketHandlerInterceptor()).withSockJS();
    }

    @Bean
    public TextWebSocketHandler webSocketHandler(){

        return new SpringWebSocketHandler();
    }

}

 第三步：繼承WebSocketHandler對象。該對象提供了客戶端連接,關閉,錯誤,發送等方法,重寫這幾個方法即可實現自定義業務邏輯

package com.example.demo.config;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.web.socket.CloseStatus;
import org.springframework.web.socket.TextMessage;
import org.springframework.web.socket.WebSocketSession;
import org.springframework.web.socket.handler.TextWebSocketHandler;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;

public class SpringWebSocketHandler extends TextWebSocketHandler {

    private static Logger logger = LoggerFactory.getLogger(SpringWebSocketHandler.class);

    private static final Map<String, WebSocketSession> users;  //Map來存儲WebSocketSession，key用USER_ID 即在線用戶列表

    //用戶標識
    private static final String USER_ID = "WEBSOCKET_USERID";   //對應監聽器從的key


    static {
        users =  new HashMap<String, WebSocketSession>();
    }

    public SpringWebSocketHandler() {}

    /**
     * 連接成功時候，會觸發頁面上onopen方法
     */
    public void afterConnectionEstablished(WebSocketSession session) throws Exception {

        System.out.println("成功建立websocket連接!");
        String userId = (String) session.getHandshakeAttributes().get(USER_ID);
        users.put(userId,session);
        System.out.println("當前線上用戶數量:"+users.size());

        //這塊會實現自己業務，比如，當用戶登錄后，會把離線消息推送給用戶
        //TextMessage returnMessage = new TextMessage("成功建立socket連接，你將收到的離線");
        //session.sendMessage(returnMessage);
    }

    /**
     * 關閉連接時觸發
     */
    public void afterConnectionClosed(WebSocketSession session, CloseStatus closeStatus) throws Exception {
        logger.debug("關閉websocket連接");
        String userId= (String) session.getHandshakeAttributes().get(USER_ID);
        System.out.println("用戶"+userId+"已退出！");
        users.remove(userId);
        System.out.println("剩余在線用戶"+users.size());
    }

    /**
     * js調用websocket.send時候，會調用該方法
     */
    @Override
    protected void handleTextMessage(WebSocketSession session, TextMessage message) throws Exception {

        super.handleTextMessage(session, message);

        /**
         * 收到消息，自定義處理機制，實現業務
         */
        System.out.println("服務器收到消息："+message);

        if(message.getPayload().startsWith("#anyone#")){ //單發某人

            sendMessageToUser((String)session.getHandshakeAttributes().get(USER_ID), new TextMessage("服務器單發：" +message.getPayload())) ;

        }else if(message.getPayload().startsWith("#everyone#")){

            sendMessageToUsers(new TextMessage("服務器群發：" +message.getPayload()));

        }else{

        }

    }

    public void handleTransportError(WebSocketSession session, Throwable exception) throws Exception {
        if(session.isOpen()){
            session.close();
        }
        logger.debug("傳輸出現異常，關閉websocket連接... ");
        String userId= (String) session.getHandshakeAttributes().get(USER_ID);
        users.remove(userId);
    }

    public boolean supportsPartialMessages() {

        return false;
    }


    /**
     * 給某個用戶發送消息
     *
     * @param userId
     * @param message
     */
    public void sendMessageToUser(String userId, TextMessage message) {
        for (String id : users.keySet()) {
            if (id.equals(userId)) {
                try {
                    if (users.get(id).isOpen()) {
                        users.get(id).sendMessage(message);
                    }
                } catch (IOException e) {
                    e.printStackTrace();
                }
                break;
            }
        }
    }

    /**
     * 給所有在線用戶發送消息
     *
     * @param message
     */
    public void sendMessageToUsers(TextMessage message) {
        for (String userId : users.keySet()) {
            try {
                if (users.get(userId).isOpen()) {
                    users.get(userId).sendMessage(message);
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

}

第四步：繼承HttpSessionHandshakeInterceptor對象。該對象作為頁面連接websocket服務的攔截器,代碼如下：

package com.example.demo.config;

import org.springframework.http.server.ServerHttpRequest;
import org.springframework.http.server.ServerHttpResponse;
import org.springframework.http.server.ServletServerHttpRequest;
import org.springframework.web.socket.WebSocketHandler;
import org.springframework.web.socket.server.support.HttpSessionHandshakeInterceptor;
import javax.servlet.http.HttpSession;
import java.util.Map;

public class SpringWebSocketHandlerInterceptor extends HttpSessionHandshakeInterceptor {
    @Override
    public boolean beforeHandshake(ServerHttpRequest request, ServerHttpResponse response, WebSocketHandler wsHandler,
                                   Map<String, Object> attributes) throws Exception {
        System.out.println("Before Handshake");
        if (request instanceof ServletServerHttpRequest) {
            ServletServerHttpRequest servletRequest = (ServletServerHttpRequest) request;
            HttpSession session = servletRequest.getServletRequest().getSession(false);
            if (session != null) {
                //使用userName區分WebSocketHandler，以便定向發送消息
                String userName = (String) session.getAttribute("SESSION_USERNAME");  //一般直接保存user實體
                if (userName!=null) {
                    attributes.put("WEBSOCKET_USERID",userName);
                }

            }
        }
        return super.beforeHandshake(request, response, wsHandler, attributes);
    }

    @Override
    public void afterHandshake(ServerHttpRequest request, ServerHttpResponse response, WebSocketHandler wsHandler,
                               Exception ex) {
        super.afterHandshake(request, response, wsHandler, ex);
    }
}

第5步 讓SpringWebSocketConfig配置類隨spring容器啟動 spring文件中加入如下代碼：

<!-- 掃描web相關的bean -->
<context:component-scan base-package="com.example.demo.controller,com.example.demo.config"/>

-------------------------------------------------------------------------到這里就算完成啦 下面准備測試-------------------------------------------------------------

1.定義一個控制器用來做連接標識和發送消息

package com.example.demo.controller;

import com.example.demo.config.SpringWebSocketHandler;
import org.springframework.context.annotation.Bean;
import org.springframework.stereotype.Controller;
import org.springframework.util.StringUtils;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.socket.TextMessage;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

@Controller
public class WebSocketController {

    @Bean//這個注解會從Spring容器拿出Bean
    public SpringWebSocketHandler infoHandler() {
        return new SpringWebSocketHandler();
    }

    @RequestMapping("/websocket/toLogin")
    public ModelAndView toLogin(HttpServletRequest request, HttpServletResponse response) throws Exception {
        return new ModelAndView("login");
    }

    @RequestMapping("/websocket/login")
    public ModelAndView login(HttpServletRequest request, HttpServletResponse response) throws Exception {
        String username = request.getParameter("username");
        System.out.println(username+"登錄");
        HttpSession session = request.getSession(false);
        session.setAttribute("SESSION_USERNAME", username);
        //response.sendRedirect("/quicksand/jsp/websocket.jsp");
        return new ModelAndView("websocket");
    }

    @RequestMapping("/websocket/send")
    @ResponseBody
    public String send(HttpServletRequest request) {
        String username = request.getParameter("username");
        if (StringUtils.isEmpty(username)){
            infoHandler().sendMessageToUsers(new TextMessage("給所有用戶發消息"));
        }else{
            infoHandler().sendMessageToUser(username, new TextMessage("給"+username+"用戶發消息"));
        }
        return null;
    }

}

2.建立登錄頁面

<%@ page language="java" contentType="text/html; charset=utf-8"
         pageEncoding="utf-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<body>
<h2>Hello World!</h2>
<body>
<form action="http://localhost:8080/demo/websocket/login">
    登錄名：<input type="text" name="username"/>
    <input type="submit" value="登錄"/>
</form>
</body>
</body>
</html>

3.建立發消息頁面

<%@ page language="java" contentType="text/html; charset=utf-8"
         pageEncoding="utf-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
    <title>Insert title here</title>
</head>
<body>
<script type="text/javascript" src="http://cdn.bootcss.com/jquery/3.1.0/jquery.min.js"></script>
<script type="text/javascript" src="http://cdn.bootcss.com/sockjs-client/1.1.1/sockjs.js"></script>
<script type="text/javascript">
    var websocket = null;
    if ('WebSocket' in window) {//判斷瀏覽器是否支持WebSocket
        websocket = new WebSocket("ws://localhost:8080/demo/websocket/socketServer.do");
    }
    else if ('MozWebSocket' in window) {
        websocket = new MozWebSocket("ws://localhost:8080/demo/websocket/socketServer.do");
    }
    else {
        websocket = new SockJS("http://localhost:8080/demo/sockjs/socketServer.do");
    }
    websocket.onopen = onOpen;
    websocket.onmessage = onMessage;
    websocket.onerror = onError;
    websocket.onclose = onClose;

    function onOpen(result) {
        alert("連接建立時觸發:"+result.data);
    }

    function onMessage(result) {
        alert("客戶端接收服務端數據時觸發:"+result.data);
    }
    function onError(result) {
        alert("通信發生錯誤時觸發:"+result.data);
    }
    function onClose(result) {
        alert("連接關閉時觸發:"+result.data);
    }
    //使用連接發送數據
    function doSend() {
        if (websocket.readyState == websocket.OPEN) {
            var msg = document.getElementById("inputMsg").value;
            websocket.send(msg);//調用后台handleTextMessage方法
            alert("發送成功!");
        } else {
            alert("連接失敗!");
        }
    }
    //窗口關閉時,將websocket連接關閉
    window.close=function()
    {
        websocket.onclose();
    }
</script>
請輸入：<textarea rows="5" cols="10" id="inputMsg" name="inputMsg"></textarea>
<button onclick="doSend();">發送</button>
</body>
</html>

測試結果如下圖：