【WebSocket】websocket学习【二】

1.需求：通过websocket实现在线聊天室

2.流程分析

3.消息格式

• 客户端 --> 服务端

{"toName":"张三","message":"你好"}
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• 服务端 --> 客户端

1. 系统消息格式：{"system":true,"fromName":null,"message"：["李四","王五"]}
2. 推送给某一个用户的消息格式：{"system":false,"fromName":"张三","message"："你好"}

4.代码实现

4.1.引入坐标

在pom.xml 中引入依赖

 <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-websocket</artifactId>
 </dependency>
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4.2.编写配置类，扫描添加有@ServerEndpoint注解的 Bean

package com.itheima.config;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.socket.server.standard.ServerEndpointExporter;

/**
 * @version v1.0
 * @ClassName: WebsocketConfig
 * @Description: TODO(一句话描述该类的功能)
 * @Author:
 */
@Configuration
public class WebsocketConfig {

    @Bean
    public ServerEndpointExporter serverEndpointExporter() {
        return new ServerEndpointExporter();
    }
}
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4.3.编写配置类，用于获取 HttpSession 对象

package com.itheima.config;

import javax.servlet.http.HttpSession;
import javax.websocket.HandshakeResponse;
import javax.websocket.server.HandshakeRequest;
import javax.websocket.server.ServerEndpointConfig;

/**
 * @version v1.0
 * @ClassName: GetHttpSessionConfig
 * @Description: TODO(一句话描述该类的功能)
 * @Author: 
 */
public class GetHttpSessionConfig extends ServerEndpointConfig.Configurator {

    @Override
    public void modifyHandshake(ServerEndpointConfig sec, HandshakeRequest request, HandshakeResponse response) {
        //获取HttpSession对象
        HttpSession httpSession = (HttpSession) request.getHttpSession();
        //将httpSession对象保存起来
        sec.getUserProperties().put(HttpSession.class.getName(),httpSession);
    }
}
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4.4.编写ChatEndpoint类 在 @ServerEndpoint 注解中引入配置器

package com.itheima.ws;

import com.alibaba.fastjson.JSON;
import com.itheima.config.GetHttpSessionConfig;
import com.itheima.utils.MessageUtils;
import com.itheima.ws.pojo.Message;
import org.springframework.stereotype.Component;

import javax.servlet.http.HttpSession;
import javax.websocket.*;
import javax.websocket.server.ServerEndpoint;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;

/**
 * @version v1.0
 * @ClassName: ChatEndpoint
 * @Description: TODO(一句话描述该类的功能)
 * @Author:
 */
@ServerEndpoint(value = "/chat",configurator = GetHttpSessionConfig.class)
@Component
public class ChatEndpoint {

    private static final Map<String,Session> onlineUsers = new ConcurrentHashMap<>();

    private HttpSession httpSession;

    /**
     * 建立websocket连接后，被调用
     * @param session
     */
    @OnOpen
    public void onOpen(Session session, EndpointConfig config) {
        //1，将session进行保存
        this.httpSession = (HttpSession) config.getUserProperties().get(HttpSession.class.getName());
        String user = (String) this.httpSession.getAttribute("user");
        onlineUsers.put(user,session);
        //2，广播消息。需要将登陆的所有的用户推送给所有的用户
        String message = MessageUtils.getMessage(true,null,getFriends());
        broadcastAllUsers(message);
    }

    public Set getFriends() {
        Set<String> set = onlineUsers.keySet();
        return set;
    }

    private void broadcastAllUsers(String message) {
        try {
            //遍历map集合
            Set<Map.Entry<String, Session>> entries = onlineUsers.entrySet();
            for (Map.Entry<String, Session> entry : entries) {
                //获取到所有用户对应的session对象
                Session session = entry.getValue();
                //发送消息
                session.getBasicRemote().sendText(message);
            }
        } catch (Exception e) {
            //记录日志
        }
    }

    /**
     * 浏览器发送消息到服务端，该方法被调用
     *
     * 张三  -->  李四
     * @param message
     */
    @OnMessage
    public void onMessage(String message) {
        try {
            //将消息推送给指定的用户
            Message msg = JSON.parseObject(message, Message.class);
            //获取 消息接收方的用户名
            String toName = msg.getToName();
            String mess = msg.getMessage();
            //获取消息接收方用户对象的session对象
            Session session = onlineUsers.get(toName);
            String user = (String) this.httpSession.getAttribute("user");
            String msg1 = MessageUtils.getMessage(false, user, mess);
            session.getBasicRemote().sendText(msg1);
        } catch (Exception e) {
            //记录日志
        }
    }

    /**
     * 断开 websocket 连接时被调用
     * @param session
     */
    @OnClose
    public void onClose(Session session) {
        //1,从onlineUsers中剔除当前用户的session对象
        String user = (String) this.httpSession.getAttribute("user");
         if (user != null) {
            onlineUsers.remove(user);
            //2,通知其他所有的用户，当前用户下线了
            String message = MessageUtils.getMessage(true, null, getFriends());
            broadcastAllUsers(message);
        } else {
            // 处理 user 为空的情况，可以记录日志或者采取其他适当的措施
        }
    }
}
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4.5.完整代码如下：

github：https://github.com/RanGuMo/itheima_chat.git