Data Binding Error Handling in Spring MVC

Question

I have a question about data binding in Spring MVC.

I have a Controller which accepts a JSON request in the form of @RequestBody. I have all the JSR 303 validations in place and it works like a charm.

• JSON Request

  public class TestJSONRequest {
  
      @Size(min=10,message="{invalid.demo.size}")
      String demo;
  
      int code;
  }
  

• Controller

  @Controller
  @RequestMapping("/test")
  public class TestController {
  
      public void testEntry(@RequestBody TestJSONRequest jsonRequest,ModelMap map)
  
        Set<ConstraintViolation<TestJSONRequest>> violationList = validator.val(jsonRequest);
        ....
        ....
        TestJSONResponse response = // Do complex Logic.
        modelMap.addattribute("TestJSONResponse",response);
      }
  }
  

But JSR 303 validations kick in once the incoming JSON data is bound to the Request object.

If I send ab in the code field of the input JSON request, binding would itself fail.

How do I handle that?

I want to catch those data binding errors and do some kind of generalized error handling in my controller.

Could you please help me out on this?

P.S - I am using Spring 3.0.3

Answer 1

According to the current Spring documentation (V3.1) :

Unlike @ModelAttribute parameters, for which a BindingResult can be used to examine the errors, @RequestBody validation errors always result in a MethodArgumentNotValidException being raised. The exception is handled in the DefaultHandlerExceptionResolver, which sends a 400 error back to the client.

Now you can to tell Spring that you'd like to handle this, by creating a new method, as follows:

@ExceptionHandler(MethodArgumentNotValidException.class)
public String handleValidation(MethodArgumentNotValidException e, ModelMap map) {
    List<ObjectError> errors = e.getBindingResult() .getAllErrors();
    // your code here...
    return "path/to/your/view";
}

Finally, have a read of the Spring docs wrt @ExceptionHandler. There's most likely some useful information there.