question: public static Response invalidEntity ( ConstraintViolationException e ) { StringBuilder errorMessage = new StringBuilder ( ) ; boolean firstPass = true ; for ( ConstraintViolation error : e . getConstraintViolations ( ) ) { if ( ! firstPass ) { errorMessage . append ( ", " ) ; } errorMessage . append ( String . format ( "%s %s (was %s)" , error . getPropertyPath ( ) , error . getMessage ( ) , error . getInvalidValue ( ) ) ) ; firstPass = false ; } ExternalException externalException = new ExternalException ( ErrorCode . INVALID_ENTITY , errorMessage . toString ( ) , null ) ; return externalException ( externalException ) ; }
target:  return an error response generated by a validation failure, invalid json, etc.