第49月第6天 spring websocket实现前后端通信

步骤二：编辑SpringWebSocketConfig，根据spring文档，编写websocketConfig，这里可参看文档，xml配置和使用注解两种方式，我选择注解方式

registerWebSocketHandlers：这个方法是向spring容器注册一个handler地址，我把他理解成requestMapping

addInterceptors：拦截器，当建立websocket连接的时候，我们可以通过继承spring的HttpSessionHandshakeInterceptor来搞事情。

setAllowedOrigins：跨域设置，*表示所有域名都可以，不限制， 域包括ip：port, 指定*可以是任意的域名，不加的话默认localhost+本服务端口

withSockJS： 这个是应对浏览器不支持websocket协议的时候降级为轮询的处理。

@Configuration
@EnableWebSocket
public class SpringWebSocketConfig implements WebSocketConfigurer {
    
    public void registerWebSocketHandlers(WebSocketHandlerRegistry registry) {
        registry.addHandler(webSocketHandler(),"/websocket/socketServer")
                .addInterceptors(new SpringWebSocketHandlerInterceptor()).setAllowedOrigins("*");
        
        registry.addHandler(webSocketHandler(), "/sockjs/socketServer").setAllowedOrigins("http://localhost:28180")
               .addInterceptors(new SpringWebSocketHandlerInterceptor()).withSockJS();
    }
 
    @Bean
    public TextWebSocketHandler webSocketHandler(){
 
        return new SpringWebSocketHandler();
    }
 
}

步骤三：编写SpringWebSocketHandlerInterceptor

这个是创建websocket连接是的拦截器，记录建立连接的用户的session以便根据不同session来通信

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区分WebSocketHandler，以便定向发送消息
                String userName = (String) session.getAttribute("SESSION_USERNAME");  //一般直接保存user实体
                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);
    }
 
}

步骤四：编写SpringWebSocketHandler 

public class SpringWebSocketHandler extends TextWebSocketHandler {
    
 
    private static final Map<String, WebSocketSession> users;  //Map来存储WebSocketSession，key用USER_ID 即在线用户列表
 
    //用户标识
    private static final String USER_ID = "WEBSOCKET_USERID";   //对应监听器从的key
 
 
    static {
        users =  new HashMap<String, WebSocketSession>();
    }
 
    public SpringWebSocketHandler() {}
 
    /**
     * 连接成功时候，会触发页面上onopen方法
     */
    public void afterConnectionEstablished(WebSocketSession session) throws Exception {
 
        System.out.println("成功建立websocket连接!");
        String userId = (String) session.getAttributes().get(USER_ID);
        users.put(userId,session);
        System.out.println("当前线上用户数量:"+users.size());
 
        //这块会实现自己业务，比如，当用户登录后，会把离线消息推送给用户
        //TextMessage returnMessage = new TextMessage("成功建立socket连接，你将收到的离线");
        //session.sendMessage(returnMessage);
    }
 
    /**
     * 关闭连接时触发
     */
    public void afterConnectionClosed(WebSocketSession session, CloseStatus closeStatus) throws Exception {
        String userId= (String) session.getAttributes().get(USER_ID);
        System.out.println("用户"+userId+"已退出！");
        users.remove(userId);
        System.out.println("剩余在线用户"+users.size());
    }
 
    /**
     * js调用websocket.send时候，会调用该方法
     */
    @Override
    protected void handleTextMessage(WebSocketSession session, TextMessage message) throws Exception {
 
        super.handleTextMessage(session, message);
 
        /**
         * 收到消息，自定义处理机制，实现业务
         */
        System.out.println("服务器收到消息："+message);
 
        if(message.getPayload().startsWith("#anyone#")){ //单发某人
 
             sendMessageToUser((String)session.getAttributes().get(USER_ID), new TextMessage("服务器单发：" +message.getPayload())) ;
 
        }else if(message.getPayload().startsWith("#everyone#")){
 
             sendMessageToUsers(new TextMessage("服务器群发：" +message.getPayload()));
 
        }else{
 
        }
 
    }
 
    public void handleTransportError(WebSocketSession session, Throwable exception) throws Exception {
        if(session.isOpen()){
            session.close();
        }
        System.out.println("传输出现异常，关闭websocket连接... ");
        String userId= (String) session.getAttributes().get(USER_ID);
        users.remove(userId);
    }
 
    public boolean supportsPartialMessages() {
 
        return false;
    }
 
 
    /**
     * 给某个用户发送消息
     *
     * @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;
            }
        }
    }
 
    /**
     * 给所有在线用户发送消息
     *
     * @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();
            }
        }
    }
 
}

步骤五：配置文件扫描config类  我的SpringWebSocketConfig配置在包com.thunisoft.config下

    <context:component-scan base-package="com.thunisoft.ssm.controller,com.thunisoft.config"></context:component-scan>