Hi James, Feel free to publish this back to the mailing list, if you'd like. Thanks for the example, I have some follow-up questions: - How does the class get hooked up to the rest of the framework? Is it through the @Provider annotation? Yes. The @Provider annotation is what registers it.

- Do you need to have multiple ParamConverterProviders? i.e. one for for integers, strings, lists, enums, etc? If you want to handle multiple types as parameters There are some default providers for sure and I wouldn't suggest doing one

- I see in your example that there is a clause if (!rawType.isEnum()) - does that mean that every single ParamConverterProvider is applied to every single parameter? If you have 100 providers, could this cause performance issues? Is there a way to associate a converter provider to a particular type? To my knowledge yes, each ParamConverterProvider is invoked on each

Thanks for the help, Arwin ------------------------------ *From:* James Perkins <jperkins(a)redhat.com&gt; *Sent:* January 25, 2022 5:13 PM *To:* Arwin Tio <arwin.tio(a)hotmail.com&gt; *Subject:* Re: [resteasy] How to show helpful error messages for malformed @QueryParam? Hi Arwin, I meant to reply to the list, but I guess I just replied directly instead :) I apologize for that. I'll keep it private for now in case you don't want any of the information public. What you could use is a ParamConverter. Something like this may work https://gist.github.com/jamezp/aad75e83760f565f15f4f0b54e202620. On Tue, Jan 25, 2022 at 5:03 PM Arwin Tio <arwin.tio(a)hotmail.com&gt; wrote: Hi James, Thanks for the reply. Sorry, there is a mistake in my example. In my particular case, I have an endpoint that takes a "status" enum: localhost:8080/api/v1/users?status=creating But when I use the wrong status, it will throw an exception: java.lang.IllegalArgumentException: No enum constant com.data.model.UserStatus.creating at java.base/java.lang.Enum.valueOf(Enum.java:273) But the client will only receive a 404, with no error message. What I was trying to say in the original email was, if number_param received something like a String: localhost:8080/api/v1/users?number_param=asdf Then it will also return a 404 as a client error, due to this exception Caused by: java.lang.NumberFormatException: For input string: "asdf" at java.base/java.lang.NumberFormatException.forInputString(NumberFormatException.java:67) What I am trying to figure out, is, instead of an opaque 404, I would like to set it up to return helpful error messages to the client, such as: - 'number_param' received 'asdf', expected a number/integer instead of a string - 'status' received 'creating', valid values are ['created', 'pending', 'complete'] Thanks, Arwin ------------------------------ *From:* James Perkins <jperkins(a)redhat.com&gt; *Sent:* January 25, 2022 4:31 PM *To:* Arwin Tio <arwin.tio(a)hotmail.com&gt; *Subject:* Re: [resteasy] How to show helpful error messages for malformed @QueryParam? Hello Arwin, Sorry for the late reply. What kind of argument is "123"? What I mean is it a linked to an enum or special value of some sort? On Fri, Jan 21, 2022 at 9:05 AM Arwin Tio <arwin.tio(a)hotmail.com&gt; wrote: As I understand it, a malformed @QueryParam will return a 404 with no message. For example, localhost:8080/api/v1/users?number_param=123 will respond with 404. Apparently, this is due to the JAX-RS spec: ``` 3.2 Fields and Bean Properties if the field or property is annotated with @MatrixParam, @QueryParam or @PathParam then an implementation MUST generate an instance of NotFoundException (404 status) that wraps the thrown exception and no entity ``` I would like the modify this behavior to: 1. Return a 400 status code, as I believe 404 causes confusion for users (they will think the endpoint doesn't exist) 2. Show a helpful error message, for example "'123' is an invalid input for number_param, expected number" I have read that the way to do this is with the ExceptionMapper<E extends Throwable> interface. Is this true? And if so, which Exception E should I use? Is there something like a QueryParamException? If it matters, I am using RESTEasy with Quarkus. Thanks, Arwin _______________________________________________ resteasy mailing list -- resteasy(a)lists.jboss.org To unsubscribe send an email to resteasy-leave(a)lists.jboss.org -- James R. Perkins JBoss by Red Hat -- James R. Perkins JBoss by Red Hat