java.lang.IllegalStateException: javax.websocket.server.ServerContainer not available

This error occurs when the Java application is trying to use the WebSocket API, but the WebSocket server container is not available.

There could be several reasons for this error, such as:

1. The WebSocket server container is not properly configured or initialized.
2. The WebSocket server container is not available on the server where the application is deployed.
3. The application is trying to use the WebSocket API in a non-WebSocket environment.

To resolve this issue, you can try the following solutions:

1. Check if the WebSocket server container is properly configured and initialized. Make sure that all the necessary dependencies are included in the classpath.
2. Verify that the WebSocket server container is available on the server where the application is deployed. If not, install the WebSocket server container and configure it properly.
3. Ensure that the application is running in a WebSocket environment and not in a non-WebSocket environment.

If these solutions do not resolve the issue, you can seek help from a Java expert or consult the WebSocket API documentation for further guidance.