SpringMVC 使用websocket向前端实时推送信息

一、maven项目添加websocket依赖
在pom.xml中添加依赖

二、项目中添加websocket相关配置

1、创建一个WebSocket配置类（这里也可以用配置文件来实现其实），实现接口来配置Websocket请求的路径和拦截器

package com.example.websocket;


import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import org.springframework.stereotype.Component;
import org.springframework.web.socket.WebSocketHandler;
import org.springframework.web.socket.config.annotation.EnableWebSocket;
import org.springframework.web.socket.config.annotation.WebSocketConfigurer;
import org.springframework.web.socket.config.annotation.WebSocketHandlerRegistry;
@Configuration
@EnableWebSocket
public class WebSocketConfig implements WebSocketConfigurer {

    @Override
    public void registerWebSocketHandlers(WebSocketHandlerRegistry registry) {
        registry.addHandler(myHandler(), "/myHandler").addInterceptors(new WebSocketInterceptor()).setAllowedOrigins("*");
    }

    @Bean
    public WebSocketHandler myHandler() {
        return new MyHandler();
    }

}

加个setAllowedOrigins(“*”)不然可能会报403的错误

3、创建拦截器，用来记录用户标识，便于后面向特定用户发送消息

package com.example.websocket;

import org.springframework.http.server.ServerHttpRequest;
import org.springframework.http.server.ServerHttpResponse;
import org.springframework.http.server.ServletServerHttpRequest;
import org.springframework.stereotype.Component;
import org.springframework.web.socket.WebSocketHandler;
import org.springframework.web.socket.server.HandshakeInterceptor;

import javax.servlet.http.HttpSession;
import java.util.Map;

@Component
public class WebSocketInterceptor implements HandshakeInterceptor {

    @Override
    public boolean beforeHandshake(ServerHttpRequest request, ServerHttpResponse response, WebSocketHandler handler, Map<String, Object> map) throws Exception {
        if (request instanceof ServletServerHttpRequest) {
            ServletServerHttpRequest serverHttpRequest = (ServletServerHttpRequest) request;
            HttpSession session = serverHttpRequest.getServletRequest().getSession();
            if (session != null) {
                map.put("username", session.getAttribute("username"));
            }

        }
        return true;
    }

    @Override
    public void afterHandshake(ServerHttpRequest serverHttpRequest, ServerHttpResponse serverHttpResponse, WebSocketHandler webSocketHandler, Exception e) {

    }
}

4、实现Websocket建立连接、发送消息、断开连接等时候的处理类。

package com.example.websocket;

import org.springframework.stereotype.Component;
import org.springframework.stereotype.Service;
import org.springframework.web.socket.CloseStatus;
import org.springframework.web.socket.TextMessage;
import org.springframework.web.socket.WebSocketMessage;
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;
import java.util.Set;

@Service
public class MyHandler extends TextWebSocketHandler {
    //在线用户列表
    private static final Map<String, WebSocketSession> users;
    //用户标识
    private static final String CLIENT_ID = "username";

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

    @Override
    public void afterConnectionEstablished(WebSocketSession session) throws Exception {
        System.out.println("成功建立连接");
        String username= getClientId(session);
        System.out.println("5555"+username);
        if (username != null) {
            users.put(username, session);
            session.sendMessage(new TextMessage("成功建立socket连接"));
            System.out.println(username);
            System.out.println(session);
        }
    }

    @Override
    public void handleTextMessage(WebSocketSession session, TextMessage message) {
        // ...
        System.out.println(message.getPayload());

        WebSocketMessage message1 = new TextMessage("server:"+message);
        try {
            session.sendMessage(message1);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    /**
     * 发送信息给指定用户
     * @param clientId
     * @param message
     * @return
     */
    public boolean sendMessageToUser(String clientId, TextMessage message) {
        if (users.get(clientId) == null) {
            System.out.println("1313313");
            return false;
        }
        WebSocketSession session = users.get(clientId);
        System.out.println("sendMessage:" + session);
        if (!session.isOpen()) {
            System.out.println("7657");
            return false;
        }
        try {
            session.sendMessage(message);
        } catch (IOException e) {
            System.out.println(e);
            return false;
        }
        return true;
    }

    /**
     * 广播信息
     * @param message
     * @return
     */
    public boolean sendMessageToAllUsers(TextMessage message) {
        boolean allSendSuccess = true;
        Set<String> clientIds = users.keySet();
        WebSocketSession session = null;
        for (String clientId : clientIds) {
            try {
                session = users.get(clientId);
                if (session.isOpen()) {
                    session.sendMessage(message);
                }
            } catch (IOException e) {
                e.printStackTrace();
                allSendSuccess = false;
            }
        }

        return  allSendSuccess;
    }


    @Override
    public void handleTransportError(WebSocketSession session, Throwable exception) throws Exception {
        if (session.isOpen()) {
            session.close();
        }
        System.out.println("连接出错");
        users.remove(getClientId(session));
    }

    @Override
    public void afterConnectionClosed(WebSocketSession session, CloseStatus status) throws Exception {
        System.out.println("连接已关闭：" + status);
        users.remove(getClientId(session));
    }

    @Override
    public boolean supportsPartialMessages() {
        return false;
    }

    /**
     * 获取用户标识
     * @param session
     * @return
     */
    private String getClientId(WebSocketSession session) {
        try {
            String clientId = (String) session.getAttributes().get(CLIENT_ID);
            return clientId;
        } catch (Exception e) {
            return null;
        }
    }
}

5、controller

@Controller
public class SocketController {

    @Autowired
    MyHandler handler;


    @RequestMapping("/login/{username}")
    public @ResponseBody String login(HttpSession session, @PathVariable("username") String username) {
        System.out.println("登录接口,username="+usename);
        session.setAttribute("username", username);
        System.out.println(session.getAttribute("username"));

        return "成功";
    }

    @RequestMapping("/message")
    public @ResponseBody String sendMessage() {
        boolean flag = handler.sendMessageToAllUser(4, new TextMessage("你好"));
        System.out.println(flag);
        return "发送";
    }

}

6、前端

//建立websocket
var ws = new WebSocket("ws://localhost:8080/你的项目名/myHandler")