Websocket实现前后台通信，demo小测试

　　新需求大概如下：用户登录系统，登录成功之后建立websocket连接，实现通信

　　总体思路：前端不是我负责，只是简单的做个功能，先实现登录，把用户标识存入HttpSeesion,再建立websocket连接，拦截器HandshakeInterceptor拦截请求，把用户标识存入Map<String, Object> attributes，然后处理器handler处理各种操作。

/**
 * @author wangqq
 * @version 创建时间：2018年11月1日 下午2:59:21
 * 实现WebSocketConfigure配置自己的socket链接
 */
@Configuration //用于定义配置类，可替换xml配置文件
@EnableWebSocket
@EnableWebMvc //启动Spring MVC特性
public class WebsocketConfig implements WebSocketConfigurer {

    @Override
    public void registerWebSocketHandlers(WebSocketHandlerRegistry registry) {
        // TODO Auto-generated method stub
        registry.addHandler(handler(), "show").addInterceptors(interceptor()).setAllowedOrigins("*");
    }

    @Bean
    public WebSocketHandler handler(){
        return new Hanlder();
    }

    @Bean
    public HandshakeInterceptor interceptor() {
        return new HandshakeInterceptor();
    }  

}

registry.addHandler第一个参数是处理器，自己可以写，第二个参数是前后台建立链接的路径，

addInterceptors 添加拦截，再握手之前之后，处理自己的业务

setAllowedOrigins 解决跨域，*代表不限，如果要指定域名则要http或者https开头

/**
 * @author wangqq
 * @version 创建时间：2018年11月1日 下午3:06:36
 * 类说明
 */
public class Hanlder extends TextWebSocketHandler {
    private Logger logger = Logger.getLogger(Hanlder.class);
    private static final Map<Integer,WebSocketSession> hotels;

    static{
        hotels = new HashMap<Integer, WebSocketSession>();
    }

    @Override
    public void afterConnectionEstablished(WebSocketSession session)
            throws Exception {
        // TODO Auto-generated method stub
        Integer hotelid = IHelper.toInteger(session.getAttributes().get("hotelid"));
        logger.info("-----------------afterConnectionEstablished-----------------");
        if(null != hotelid){
            logger.info(String.format("酒店连接，id:%s", hotelid));
            hotels.put(hotelid, session);
            JSONObject json = new JSONObject();
            json.put("code","testMessage");
            session.sendMessage(new TextMessage(json.toString()));
        }

        //super.afterConnectionEstablished(session);
    }
    /**
     * js调用websocket.send时候，会调用该方法
     */
    @Override
    protected void handleTextMessage(WebSocketSession session,
            TextMessage message) throws Exception {
        // TODO Auto-generated method stub
        logger.info(String.format("收到酒店（id:%s）发来消息,消息详情:%s", session.getAttributes().get("hotelid"),message.toString()));
        super.handleTextMessage(session, message);
        //这里可以给用户发消息
        logger.info("执行Hanlder---------客户端收到请求");
    }

    @Override
    public void afterConnectionClosed(WebSocketSession session,
            CloseStatus status) throws Exception {
        // TODO Auto-generated method stub
        Integer hotelid = IHelper.toInteger(session.getAttributes().get("hotelid"));
        logger.info(String.format("用户退出，酒店id：%s", hotelid));
        hotels.remove(hotelid);
        super.afterConnectionClosed(session, status);
    }
    /**
     * 给单个用户发消息
     * @param hotelid
     * @param message
     * @throws IOException
     */
    public void sendMessage(Integer hotelid,TextMessage message) throws Exception{
        if(hotels.containsKey(hotelid)){
            if(hotels.get(hotelid).isOpen()){
                hotels.get(hotelid).sendMessage(message);
            }
        }

    }
    /**
     * 给所有在线用户发消息
     * @param message
     * @throws IOException
     */
    public void sendMessage(TextMessage message) throws Exception{
        for(Integer id : hotels.keySet()){
            WebSocketSession session = hotels.get(id);
            if(session.isOpen()){
                session.sendMessage(message);
            }
        }
    }
    /**
     * 多个在线用户，不同消息
     * @param data
     * @throws Exception
     */
    public void sendMessage(Map<Integer, TextMessage> data) throws Exception{
        for(Map.Entry<Integer, TextMessage> entry : data.entrySet()){
            Integer hotelid = entry.getKey();
            this.sendMessage(hotelid, entry.getValue());
        }
    }
    /**
     * 多个用户，同一消息
     * @param hotelids
     * @param message
     * @throws Exception
     */
    public void sendMessage(List<Integer> hotelids,TextMessage message) throws Exception{
        for(Integer id : hotelids){
            this.sendMessage(id, message);
        }
    }
}

/**
 * @author wangqq
 * @version 创建时间：2018年11月2日 下午1:42:00
 * 类说明
 */
public class HandshakeInterceptor extends HttpSessionHandshakeInterceptor {

    private Logger logger = Logger.getLogger(HandshakeInterceptor.class);

    @Override
    public boolean beforeHandshake(ServerHttpRequest request,
            ServerHttpResponse response, WebSocketHandler wsHandler,
            Map<String, Object> attributes) throws Exception {
        // TODO Auto-generated method stub
        logger.info("-----------beforeHandshake---------");
        if(request instanceof ServletServerHttpRequest){
            ServletServerHttpRequest serverHttpRequest = (ServletServerHttpRequest)request;
            HttpSession session = serverHttpRequest.getServletRequest().getSession();
            if(null != session){
                logger.info("拦截请求，存入attribute,酒店id:"+session.getAttribute("hotelid"));
                if(null!=session.getAttribute("hotelid")){
                    attributes.put("hotelid", session.getAttribute("hotelid"));
                }
            }
        }
        return super.beforeHandshake(request, response, wsHandler, attributes);
    }

    @Override
    public void afterHandshake(ServerHttpRequest request,
            ServerHttpResponse response, WebSocketHandler wsHandler,
            Exception ex) {
        // TODO Auto-generated method stub
        logger.info("-----------afterHandshake--------------");
        super.afterHandshake(request, response, wsHandler, ex);
    }
}

前端页面（简单的不能再简单，没有考虑浏览器支不支持）

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">

    <title>My JSP 'index.jsp' starting page</title>

    <meta http-equiv="pragma" content="no-cache">
    <meta http-equiv="cache-control" content="no-cache">
    <meta http-equiv="expires" content="0">
    <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
    <meta http-equiv="description" content="This is my page">
    <!--
    <link rel="stylesheet" type="text/css" href="styles.css">
    -->
    <script language="JavaScript" src="jquery/jquery-1.11.3.min.js" charset="UTF-8"></script>
    <script type="text/javascript">
        var ws =
        $(function(){
            $.ajaxSettings.async=false;
            $.post('<%=basePath%>/show/doSaveSession',{'hotelid':1},function(data){
                console.log("执行保存session");//模拟先登录
            });
            $.ajaxSettings.async=true;
            ws = new WebSocket("ws://localhost:7001/show");

           ws.onopen = function () {
              console.log("建立链接");

           }
           ws.onclose = function () {
              console.log("onclose");
           }

           ws.onmessage = function (msg) {
                   console.log("----------------");
                console.log(msg.data);
           }
        });

    </script>

  </head>

  <body>
    This is my JSP page. <br>

  </body>
</html>

执行结果：

前台

后台：

ps:2018-11-19 更新，后来测试一下，不用提前登陆，直接在前端连socket的路径上面加参数，而后在拦截器的

beforeHandshake中就可把连接的用户存入map