How to show helpful error messages for malformed @QueryParam?
by Arwin Tio
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
4 years, 1 month
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