BindException validation built-in support

I would discuss with you if org.springframework.validation.BindException could be a great candidate to be a built-in managed exception.

Indeed when you’re validating query params rather than post body like following

@RequestMapping(path = "/handler-invalid-query-strings", method = GET)
public ResponseEntity<String> validRequestQueryStrings(@Valid final PageRequest pageRequest) {
    return ResponseEntity.ok("done");
}

With PageRequest looks like

@Data
public final class PageRequest {

    @Min(value = 0)
    private int page = 0;

    @Min(value = 1)
    private int size = 50;
}

If you try

@Test
public void invalidRequestQueryParams() throws Exception {
    mvc().perform(request(GET, "http://localhost/api/handler-invalid-query-strings?page=-1"))
         .andExpect(status().isBadRequest());
}

I will fail because 500 status code will be returned after Spring will throw org.springframework.validation.BindException

---

A bit off-topic, but can explain why:

Spring MethodValidationPostProcessor works great with zalando:problem-spring-web, indeed if you replace previous GetMapping with following:

@RequestMapping(path = "/handler-invalid-query-strings", method = GET)
public ResponseEntity<String> validRequestQueryStrings(@Min(value = 0) @RequestParam(value = "page", defaultValue = "0") int page,
        @Min(value = 1) @RequestParam(value="limit", defaultValue = "50") int limit) {
    return ResponseEntity.ok("done");
}

I will work but since method parameter name is removed after compilation the result looks like:

{  
   "violations":[  
      {  
         "field":"getUsers.arg0",
         "message":"must be greater than or equal to 0"
      }
   ],
   "status":400,
   "type":"https://zalando.github.io/problem/constraint-violation",
   "title":"Constraint Violation"
}

As you can see field is equals to getUsers.arg0 which is no really user-friendly. That why I used to create a intermediate object (DTO?) for validation even for GET parameters.

[whiskeysierra]

I could also imagine to put this into the javadoc of the ConstraintViolationAdviceTrait.

[kakawait]

@whiskeysierra about doc do you really think that this edge case should be part of README.md. From my point of view README.md should be an overview of the application/library/framework and not be pollute by some special case.

Maybe just I can just create an issue to describe the problem (different from BindException support) and close it, thus using issue tracking like a kind of Q&A?