Java EE Websockets
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【中文标题】Java EE Websockets【英文标题】： 【发布时间】：2020-07-27 01:19:19 【问题描述】：Websockets，无法建立连接。 我可以覆盖方法 OnClose、OnMessage、OnOpen 等吗？ 在@ServerEndpoint Annotation 中添加“value =”有什么区别？
如何使用 RoomID 作为参数？
OnOpen(Session session, @PathParam "roomID" String roomID)?
EchoServer.java
import java.io.IOException;
import javax.websocket.OnClose;
import javax.websocket.OnMessage;
import javax.websocket.OnOpen;
import javax.websocket.Session;
import javax.websocket.server.ServerEndpoint;
import javax.ws.rs.PathParam;
@ServerEndpoint(value = "/echo/roomID")
public class EchoServer
@OnOpen
public void onOpen(Session session)
String roomID = session.getUserProperties().get("roomID").toString();
session.getUserProperties().put("roomID", roomID);
SessionHandler.addSession(session, roomID);
System.out.println(session.getId() + " has opened a connection");
try
session.getBasicRemote().sendText("Connection Established");
catch (IOException ex)
ex.printStackTrace();
@OnMessage
public void onMessage(String message, Session session)
System.out.println("Message from " + session.getId() + ": " + message);
try
session.getBasicRemote().sendText(message);
catch (Exception ex)
ex.printStackTrace();
@OnClose
public void onClose(Session session, String roomID)
SessionHandler.removeSession(session, roomID);
System.out.println("Session " +session.getId()+" has ended");
SessionHandler.java
import java.util.HashMap;
import java.util.Map;
import javax.websocket.Session;
public class SessionHandler
private static final Map<String, Session> sessions = new HashMap<>();
public static void addSession(Session session, String roomID)
sessions.put(roomID, session);
public static void removeSession(Session session, String roomID)
sessions.remove(roomID, session);
public static void sendToSession(Session session, String message)
System.out.println("Message from " + session.getId() + ": " + message);
try
session.getBasicRemote().sendText(message);
catch (Exception ex)
ex.printStackTrace();
index.html
<!DOCTYPE html>
<html>
<head>
<title>Echo Chamber</title>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width">
</head>
<body>
<div>
<input type="number" id="roomID"/>
<input type="text" id="messageinput"/>
</div>
<div>
<button type="button" onclick="openSocket();" >Open</button>
<button type="button" onclick="send();" >Send</button>
<button type="button" onclick="closeSocket();" >Close</button>
</div>
<!-- Server responses get written here -->
<div id="messages"></div>
<!-- Script to utilise the WebSocket -->
<script type="text/javascript">
var webSocket;
var messages = document.getElementById("messages");
function openSocket()
if(webSocket !== undefined && webSocket.readyState !== WebSocket.CLOSED)
writeResponse("WebSocket is already opened.");
return;
webSocket = new WebSocket("ws://localhost:8080/EchoChamber/echo/"+document.getElementById("roomID").value+"");
webSocket.onopen = function(event)
if(event.data === undefined)
return;
writeResponse(event.data);
;
webSocket.onmessage = function(event)
writeResponse(event.data);
;
webSocket.onclose = function(event)
writeResponse("Connection closed");
;
function send()
var text = document.getElementById("messageinput").value;
webSocket.send(text);
function closeSocket()
webSocket.close();
function writeResponse(text)
messages.innerHTML += "<br/>" + text;
</script>
</body>
</html>
【问题讨论】：
【参考方案1】：好的，看起来像默认方法
onClose(Session session)
应该只接受 1 个参数，我的方法
onClose(Session session, String roomID)
错了。它修复了使用默认方法的所有问题
【讨论】：
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