Question

我尝试使用eclipse ide进行websocket通信，当我运行我的代码时，我得到一个NullPointerException。我已经检查过，getAttribute中的名称与bean中的名称相同

package ws;

import java.io.IOException;
import java.util.Set;
import java.util.concurrent.CopyOnWriteArraySet;

import javax.websocket.server.ServerEndpoint;

import fundstarter.model.ConnectToRMIBean;

import javax.servlet.http.HttpSession;
import javax.websocket.*;

@ServerEndpoint(value="/ws", configurator = HandShake.class)
public class WebSocketAnnotation {

    private Session session;
    private ConnectToRMIBean sessionUser;
    private HttpSession httpSession;
    private static final Set<WebSocketAnnotation> myConnections = new CopyOnWriteArraySet<WebSocketAnnotation>();

    public WebSocketAnnotation() {

    }

    @OnOpen
    public void start(Session session, EndpointConfig config) {

        this.session = session;
        this.httpSession = (HttpSession) config.getUserProperties().get(HttpSession.class.getName());
        myConnections.add(this);
        this.sessionUser = (ConnectToRMIBean) httpSession.getAttribute("RMIBean");
        //sendMessage("New message");
    }

    @OnClose
    public void end() {
        // clean up once the WebSocket connection is closed
        myConnections.remove(this);
    }

    @OnMessage
    public void receiveMessage(String message) {
        sendMessage(message);
    }    

    @OnError
    public void handleError(Throwable t) {
        t.printStackTrace();
    }    

    private void sendMessage(String text) {
        try {
            System.out.println("[WebSocketAnnot]RMIBean User Id -> " + this.sessionUser.getUserID());
            this.session.getBasicRemote().sendText(text);

        } catch (IOException e) {
            try {
                this.session.close();
            } catch (IOException e1) {
                e1.printStackTrace();
            }
        }
    }
}

谁能告诉我我的错误是什么？

Answer 1

我发现了错误。这是关于HandShake

上的modifyHandshake方法的拼写错误

HttpSession getAttribute（）返回null

1 个答案: