Question

I have a model object which has entities annotated with hibernate validation annotations. For example @NotBlank, @NotNull, @Length.
I have a form backing this model which decorates an instance of the model object. I have annotated this instance with an @NotNull, @Valid annotation. I am registering a validator for this backing form in the Controller Class and the form validator is being invoked when the @RequestMapping method argument is annotated with @Valid annotation.

Note the model is also annotated with the @Entity annotation, the model backing form is just
a thin wrapper around the model.

However the validations on the decorated object are not being checked? I know this because in the request mapping method definition I check the BindResult for errors and there are none.
My form fields are all empty, hence the validations on the fields on the decorated model annotated with @NotBlank should be checked. However that does not happen.

Can you help me fix this?

Edit:
Sample Code

@Entity
class MyModel {
    @Id
@GeneratedValue(strategy = GenerationType.AUTO)
    @Column(nullable=false)
    private Long id;

    @NotBlank
    @Column(unique=true, length=30, nullable=false)
    private String number;

    @Column(length=30, nullable=false)
    @Length(min=1, max=30)
private String firstName;
    /* ... getters and setters ... */
}

public class MyModelBackingForm {

   @NotNull
   @Valid
   private MyModel model;
   /* ... delegate getters and setters for all fields in MyModel ...  */
 }

Edit:
Add Controller Code

@InitBinder
protected void initBinder(WebDataBinder binder) {
  binder.setValidator(new MyBackingFormValidator());
}

Edit:

public class MyBackingFormValidator implements Validator {

  public MyBackingFormValidator() {
    super();
  }

  @Override
  public boolean supports(Class<?> clazz) {
    return Arrays.asList(MyBackingForm.class, MyModel.class).contains(clazz);
  }

  @Override
  public void validate(Object obj, Errors errors) {
   // custom validation code commented ... as I want to check if JSR 303 validations invoked
  }
}

Answer 1

Here is a sample code the way I was using the hibernate validation. I was calling @valid on the fetched objects with the binding result. This way it knows the validations which are required to be done on the form.
Edited: How to invoke custom and standard validator?

Using @InitBinder we can pass the custom validator instance to which again we can pass the class parameter for the standard validator using binder.getValidator()

Courtesy: Rohit Banga

@Controller
@RequestMapping("/customer")
public class CustomerController {

//Edited:

@InitBinder 
protected void initBinder(WebDataBinder binder) { 
binder.setValidator(new CustomFormValidator(binder.getValidator())); 
}

    @RequestMapping(value = "/signup", method = RequestMethod.POST)
    public String addCustomer(@Valid Customer customer, BindingResult result) {

        if (result.hasErrors()) {
            return "form";
        } else {
            return "success";
        }

    }

    @RequestMapping(method = RequestMethod.GET)
    public String customerForm(ModelMap model) {

        model.addAttribute("customer", new Customer());
        return "form";

    }

}