Spring MVC : Preventing Exceptions when binding model attribute

Question

In my model(s) I use Numeric data types like Long, Integer etc. When I do form post of them, but supply String, it outputs Exception stack trace, including like NumberFormatException. How can i properly wrap this so that UI does not see the exception stack trace ?

Answer 1

You need to have a BindingResult argument right after the command argument (with @Value annotation) in your controller. Then you can inspect the bindingResult and decide what to do with the stuff that could`t be bind.

When you have that BindingResult argument then the controller method gets invoked, even with an binding error, and you have to handle the error yourself.

Typically it would look a bit like this example (create a user or render the user create page again):

@RequestMapping(method = RequestMethod.POST)
public ModelAndView create(@Valid UserCreateCommand userCreateCommand,
                           BindingResult bindingResult) {
   if (bindingResult.hasErrors()) {
        //or some of your handling for bindingResult errors
        return new ModelAndView("user/create", userCreateCommand", userCreateCommand);
    } else {
    ...
    }
}

---

But how do I differentiate the normal validation errors vs. validation errors occuring due to NumberFormatException ?

The BindingResult has several methods to obtain the FieldErrors, for example BindingResult.getFieldErrors(). and a FieldError has the property boolean isBindingFailure()

Answer 2

If you want to display customized message for that exception you should configure Spring to use message.properties file and specify 'typeMismatch.className.propertyName' message or global message for typeMismatch.

For example (Spring 3.2): In servlet-config.xml

<bean id="messageSource"
class="org.springframework.context.support.ReloadableResourceBundleMessageSource"
p:basename="classpath:messages/messages">
</bean>

In src/main/resources/messages/messages.properties

typeMismatch = Invalid data format!

In controller:

public String addObject(@Valid @ModelAttribute("objectForm")
ObjectForm objectForm, BindingResult result, Model model)
{
        if (result.hasErrors())
        {
            return "/addObject";
        }
    //...
}

In jsp:

<form:errors path="propertyName" cssClass="divErrorsServer" element="div" />

You can also use:

System.out.println(result.getAllErrors());

To see what codes you can add in messages file for that error. For example when I used String on private Double weight field I got those codes:

[typeMismatch.objectForm.weight,
typeMismatch.weight,
typeMismatch.java.lang.Double,
typeMismatch]