为了实现优雅重连和重试，您需要在代码中添加一些逻辑来处理连接失败或断开连接的情况。

实现代码如下：

import javax.websocket.*;
import java.io.IOException;

@ClientEndpoint
public class WebSocketClientEndpoint {

    private Session userSession = null;
    private MessageHandler messageHandler;
    private int retryCount = 0;

    public WebSocketClientEndpoint(String endpointURI) {
        try {
            WebSocketContainer container = ContainerProvider.getWebSocketContainer();
            container.connectToServer(this, URI.create(endpointURI));
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }

    @OnOpen
    public void onOpen(Session userSession) {
        System.out.println("opening websocket");
        this.userSession = userSession;
    }

    @OnClose
    public void onClose(Session userSession, CloseReason reason) {
        System.out.println("closing websocket");
        this.userSession = null;
        retryConnect();
    }

    @OnMessage
    public void onMessage(String message) {
        if (this.messageHandler != null) {
            this.messageHandler.handleMessage(message);
        }
    }

    @OnOpenException
    public void onOpenException(Exception ex) {
        System.out.println("Error opening websocket: " + ex.getMessage());
        retryConnect();
    }

    private void retryConnect() {
        if (retryCount < 5) {
            try {
                Thread.sleep(1000); // 等待1秒后重试连接
                WebSocketContainer container = ContainerProvider.getWebSocketContainer();
                container.connectToServer(this, URI.create("ws://localhost:8080/my-websocket-endpoint"));
                retryCount++;
            } catch (Exception e) {
                System.out.println("Error reconnecting: " + e.getMessage());
                retryConnect(); // 如果连接失败，继续重试连接
            }
        } else {
            System.out.println("Max retries reached, giving up.");
        }
    }

    public void sendMessage(String message) throws IOException {
        this.userSession.getBasicRemote().sendText(message);
    }

    public void addMessageHandler(MessageHandler handler) {
        this.messageHandler = handler;
    }
}