How to customize the response of failed validation when using @Valid in SpringBoot

Question

I am using @Valid together with @RequestBody to validate the request body of post call of an API endpoint, for example:

public ResponseEntity<> sendEmail(@Valid @RequestBody EmailPostBody emailPostBody) {
.
.
.
}

When the validation fails, a response as shown below is returned to the caller.

{
    "timestamp": "2020-08-04T02:57:22.839+00:00",
    "status": 400,
    "error": "Bad Request",
    "message": "Validation failed for object='emailPostBody'. Error count: 1",
    "path": "/email"
}

However, it only says "Validation failed", but doesn't indicate which field is problematic.

I would like to costumize this response to make it more specific, but don't know how.

Could anyone teach me?

Thanks!

Answer 1

1. First you need to capture the field errors using Errors .
2. Then check if errors.hasErrors() is true then you can send your custom error message in ResponseBody .

public ResponseEntity<> sendEmail(@Valid  @RequestBody EmailPostBody emailPostBody, 
                                  Errors errors) {
    if(errors.hasErrors()) {
        new ResponseEntity<>(youResponseBodyWithErrorMsg, httpStatusCode)
    }

}