记录一个使用kotlin写WebSocket的常用模板

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package top.zfxt.chat.service

import cn.hutool.json.JSONArray
import cn.hutool.json.JSONObject
import cn.hutool.json.JSONUtil
import jakarta.websocket.*
import jakarta.websocket.server.PathParam
import jakarta.websocket.server.ServerEndpoint
import org.slf4j.LoggerFactory
import org.springframework.stereotype.Controller
import org.springframework.stereotype.Service
import top.zfxt.chat.pojo.User
import java.nio.ByteBuffer
import java.util.*
import java.util.concurrent.ConcurrentHashMap

/**
 *  @author:zfxt
 *  @version:1.0
 */
@Service
@ServerEndpoint("/chat/{username}")
class WebSocketServer {
    companion object{
          val UsersMap:MutableMap<String, User?> = mutableMapOf()

          val log = LoggerFactory.getLogger(WebSocketServer.javaClass)

        /**
         * 记录当前在线人数
         */
         val sessionMap:MutableMap<String,Session> = ConcurrentHashMap();
    }

    /**
     * 建立成功调用的方法
     */
    @OnOpen
    public fun onOpen(session:Session,@PathParam("username") username:String){
        //让用户上线
        var newUser: User? = UsersMap.get(username)
        newUser?.status = "online"
        if(newUser==null)
        {
            //生成用户信息
            var userId = UUID.randomUUID().toString().replace("-","").substring(0,10)
            newUser = User(userId,username,null,"online")

        }

            UsersMap.put(username,newUser)
            sessionMap.put(username,session)
            log.info("有新用户加入，username={}，当前在线人数为：{}",username, sessionMap.size)


        var systemMessage = JSONObject().set("isSystem",true).set("users", UsersMap.values)
        sendAllMessage(JSONUtil.toJsonStr(systemMessage))
//        var result: JSONObject = JSONObject()
//        var array: JSONArray = JSONArray()
//        result.set("users",array)
//        for (key in sessionMap.keys){
//            array.add(JSONObject().set("username",key))
//        }
//        sendAllMessage(JSONUtil.toJsonStr(result))
    }
    /**
     * 连接关闭调用的方法
     */
    @OnClose
    public fun onClose(session: Session,@PathParam("username") username: String){
        sessionMap.remove(username)
        UsersMap.remove(username)
        log.info("有一连接关闭，移除username={}的用户session，当前在线人数为：{}",username, sessionMap.size)
        var systemMessage = JSONObject().set("isSystem",true).set("users", UsersMap.values)
        sendAllMessage(JSONUtil.toJsonStr(systemMessage))
    }
    /**
     * 收到客户端消息后调用的方法
     *
     * @param message 客户端发送过来的消息
     */
    @OnMessage(maxMessageSize = 1024*1024*10)
    public fun onMessage(message: String,@PathParam("username") username: String){
        log.info("服务器收到用户username={}的消息:{}",username,message)
        var obj = JSONUtil.parseObj(message)
        var fromname = obj.getStr("from")
        var toUsername = obj.getStr("to")
        var toSession = sessionMap.get(toUsername)
        if(toSession != null){
            var message = JSONObject().set("isSystem",false).set("message",obj).toString()
            sendMassage(message,toSession)
            log.info("用户{}发送给用户username={}，消息：{}",fromname,toUsername,message)
        }else{
            log.info("发送失败，未找到用户username={}的session",toUsername)
            UsersMap.remove(toUsername)
        }
    }
    @OnError
    public fun onError(session: Session,error:Throwable){
        log.error("发生错误")
        error.printStackTrace()
    }

    /**
     * 服务器发送消息给客户端
     */
    private fun sendMassage(message:String,toSession: Session){
        try {
            log.info("服务器给客户端[{}]发送消息{}",toSession.id,message)
            toSession.basicRemote.sendText(message)
        }catch (e:Exception){
            log.error("服务器发送消息给客户端失败",e)
        }
    }
    /**
     * 服务器发送图片给客户端
     */
    private fun sendImage(image:ByteBuffer,toSession: Session){
        toSession.basicRemote.sendBinary(image)
    }
    /**
     * 服务器发送消息给所有客户端
     */
    private fun sendAllMessage(message:String){
        try {
            for(session in sessionMap.values){
                log.info("服务端给客户端[{}]发送消息{}",session.id,message)
                session.basicRemote.sendText(message)
            }
        }catch (e:Exception){
            log.error("服务器发送消息给客户端失败",e)
        }
    }
}