Is there any proper way to handle validation exceptions in @OnOpen method?

[domi-nika60]

Hi,

Just wondering if there is any way to handle exceptions in Websocket server onOpen method.
In my project I introduced validation of the parameters being sent via websocket connection.

Something like this:

@OnOpen
@Validated
public Publisher<String> onOpen(
        @Valid @RequestBean WebsocketClient data,
        WebSocketSession session
) {
...
}

And in WebsocketClient class:

@NotBlank
@PathVariable
@Pattern(regexp = "<some regexp>")
private String id;

When the id is not valid, there is an exception on OnOpen method with all stacktrace. I was trying to handle it in any way. Most reasonable was to add:
(from https://guides.micronaut.io/micronaut-error-handling/guide/index.html)

@OnOpen
@Validated
@Error(exception = ConstraintViolationException.class)
  public Publisher<String> onOpen(
        @Valid @RequestBean WebsocketClient data,
        WebSocketSession session,
        ConstraintViolationException ex
) 

And use this execption to be logged.
But then there is an error

Parameter to @OnOpen must either be a URI variable, a WebSocketSession , the HttpRequest, or annotated with an HTTP binding annotation (such as @Header)
        ConstraintViolationException ex
                                     ^

Is there any other proper way to handle validation exceptions in @onopen methods?
Maybe it is a bug?

[graemerocher]

You would need to add an @OnError handler for the WebSocket

[domi-nika60]

Does this @OnError is addressed to @Valid annotation of WebSocket data? For me it seems to not work like this.

[graemerocher]

Should do, if not provide an example in an issue. Here is an example from our test suite https://github.com/micronaut-projects/micronaut-core/blob/b52ef797a2b4f5429cd38768b5a3d2534c717c8c/http-server-netty/src/test/groovy/io/micronaut/http/server/netty/websocket/errors/MessageErrorSocketWithOnError.java

[domi-nika60]

I've made sth like this:

    @OnOpen
    @Validated
    public Publisher<String> onOpen(
        @Valid @RequestBean WebsocketClient data,
        WebSocketSession session
    ) {...}
    
    @OnError
    public void onError(ConstraintViolationException e) {
        LOG.error("Error occured: {}", e );
    }

But the OnError method is not being executed. There is no difference in application behavior and logs if OnError is there or not. Any idea why? What do I do wrong?

[domi-nika60]

Any updates about this? If not, I will rise an issue.

[graemerocher]

Seems issue report worthy