java中Websocket的使用

什么试WebSocket

WebSocket是一个连接，这个连接是客户端（页面）与服务端之间的连接，处理两者间通讯；
好处：HTML5定义了WebSocket协议，能更好的节省服务器资源和带宽，并且能够更实时地进行通讯,不需要每次发送请求接口获取数据，
使用场景：比如客户端登录后，出现的消息推送，每天定时广播推送给客户端消息等场景；

SpringBoot maven项目中实现

导入依赖：

<dependency>   <groupId>org.springframework.boot</groupId>   <artifactId>spring-boot-starter-websocket</artifactId></dependency>

客户端和服务端怎么链接呢？前端实现也是固定的写法，只需要请求/websocket/{userId} 这个地址即可实现链接

前端js代码：

//判断当前浏览器是否支持WebSocket  if ('WebSocket' in window) {      websocket = new WebSocket("ws://" + document.location.host + "/WebChat/websocket/" + username + "/"+ _img);  } else {      alert('当前浏览器 Not support websocket')  } 

java 实现websocket连接的代码:

package org.jeecg.modules.message.websocket;import com.alibaba.fastjson.JSONObject;import lombok.extern.slf4j.Slf4j;import org.jeecg.common.constant.WebsocketConst;import org.springframework.stereotype.Component;import javax.websocket.OnClose;import javax.websocket.OnError;import javax.websocket.OnMessage;import javax.websocket.OnOpen;import javax.websocket.Session;import javax.websocket.server.PathParam;import javax.websocket.server.ServerEndpoint;import java.io.IOException;import java.util.HashMap;import java.util.Map;import java.util.concurrent.CopyOnWriteArraySet;@Component@Slf4j@ServerEndpoint("/websocket/{userId}") //此注解相当于设置访问URLpublic class WebSocket {    private Session session;    private static final CopyOnWriteArraySet<WebSocket> webSockets = new CopyOnWriteArraySet<>();        private static final Map<String, Session> sessionPool = new HashMap<>();    @OnOpen    public void onOpen(Session session, @PathParam(value = "userId") String userId) {        try {            this.session = session;            webSockets.add(this);            sessionPool.put(userId, session);            log.info("【websocket消息】有新的连接，总数为: {}", webSockets.size());        } catch (Exception e) {        }    }    @OnClose    public void onClose(@PathParam(value = "userId") String userId) {        try {            webSockets.remove(this);            sessionPool.remove(userId);            log.info("【websocket消息】连接断开，总数为: {}", webSockets.size());        } catch (Exception e) {        }    }    @OnMessage    public void onMessage(String message) {        log.debug("【websocket消息】收到客户端消息: {}", message);        JSONObject obj = new JSONObject();        obj.put(WebsocketConst.MSG_CMD, WebsocketConst.CMD_CHECK);//业务类型        obj.put(WebsocketConst.MSG_TXT, "心跳响应");//消息内容        session.getAsyncRemote().sendText(obj.toJSONString());    }    @OnError    public void OnError(Session session, @PathParam(value = "userId") String userId, Throwable t) {        try {            if (session.isOpen()) {                session.close();            }            webSockets.remove(this);            sessionPool.remove(userId);            log.info("【websocket消息】连接[错误]断开，总数为: {}, 错误：{}", webSockets.size(), t.getMessage());        } catch (IOException e) {            e.printStackTrace();        }    }    // 此为广播消息    public void sendAllMessage(String message) {        log.info("【websocket消息】广播消息:" + message);        for (WebSocket webSocket : webSockets) {            try {                if (webSocket.session.isOpen()) {                    webSocket.session.getAsyncRemote().sendText(message);                }            } catch (Exception e) {                e.printStackTrace();            }        }    }    // 此为单点消息    public void sendOneMessage(String userId, String message) {        Session session = sessionPool.get(userId);        if (session != null && session.isOpen()) {            try {                log.info("【websocket消息】 单点消息:" + message);                session.getAsyncRemote().sendText(message);            } catch (Exception e) {                e.printStackTrace();            }        }    }    // 此为单点消息(多人)    public void sendMoreMessage(String[] userIds, String message) {        for (String userId : userIds) {            Session session = sessionPool.get(userId);            if (session != null && session.isOpen()) {                try {                    log.info("【websocket消息】 单点消息:" + message);                    session.getAsyncRemote().sendText(message);                } catch (Exception e) {                    e.printStackTrace();                }            }        }    }}

在RunApplication中加入：

package org.jeecg.config;import org.springframework.context.annotation.Bean;import org.springframework.context.annotation.Configuration;import org.springframework.web.socket.server.standard.ServerEndpointExporter;@Configurationpublic class WebSocketConfig {          @Bean    public ServerEndpointExporter serverEndpointExporter() {      return new ServerEndpointExporter();    }    }

可以编写一个test 测试连接

public class WebSocketTest {    public static void main(String[] args) {        try {            // 创建WebSocket客户端            MyWebSocketClient myClient = new MyWebSocketClient(new URI("ws://127.0.0.1:9091/web/websocket/123333"));            // 与服务端建立连接            myClient.connect();            while (!myClient.getReadyState().equals(ReadyState.OPEN)) {                System.out.println("连接中。。。");                Thread.sleep(1000);            }            // 往websocket服务端发送数据            myClient.send("发送来自websocketClient 123333的消息");            Thread.sleep(1000);            // 关闭与服务端的连接            // myClient.close();        }catch (Exception e){            e.printStackTrace();        }        // write your code here    }}

实际开发使用：

package org.jeecg.modules.food.job;import com.alibaba.fastjson.JSONObject;import org.apache.commons.collections.CollectionUtils;import org.jeecg.common.constant.WebsocketConst;import org.jeecg.modules.food.entity.DailyMenu;import org.jeecg.modules.food.mapper.DailyMenuMapper;import org.jeecg.modules.message.websocket.WebSocket;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.scheduling.annotation.Scheduled;import org.springframework.stereotype.Component;import javax.annotation.Resource;import java.util.Calendar;import java.util.Date;import java.util.List;@Componentpublic class DailyMenuTask {    @Resource    private WebSocket webSocket;    @Autowired    private DailyMenuMapper dailyMenuMapper;    @Scheduled(cron = "0 0 10,14 * * ?")    public void pushDailyMenu() {        DailyMenu dailyMenu = new DailyMenu();        Calendar cal = Calendar.getInstance();        cal.setTime(new Date());        cal.add(Calendar.DATE, 1);        Date time = cal.getTime();        dailyMenu.setFoodDate(time);        List<DailyMenu> dailyMenus = dailyMenuMapper.selectByDate(dailyMenu);        if (CollectionUtils.isNotEmpty(dailyMenus)) {            //创建业务消息信息            JSONObject obj = new JSONObject();            // 业务类型            obj.put(WebsocketConst.MSG_CMD, WebsocketConst.CMD_TOPIC);            obj.put(WebsocketConst.MSG_ID, dailyMenus.get(0).getId());            obj.put(WebsocketConst.MSG_TXT, "订餐发布");            //全体发送            webSocket.sendAllMessage(obj.toJSONString());        }    }}

java 实现websocket的方式有很多种

1. java 实现websocket一般两种方式，一种使用tomcat的websocket实现，比如上述使用这种方式无需别的任何配置，只需服务端一个处理类；
2. 使用spring的websocket，spring与websocket整合需要spring 4.x，并且使用了socketjs，对不支持websocket的浏览器可以模拟websocket使用。实现WebSocketConfigurer接口的registerWebSocketHandlers方法加入自己WebSocketHandler接口的实现类。
3. 使用spring stomp封装的方法，实现更简单，配置注入后通过@sendto就可向客户端发消息。
4. 等等

来源地址：https://blog.csdn.net/rainAndyou/article/details/130678911