How to perform Spring validation in MultiActionCon

How to perform Spring validation in MultiActionController?

Let's write the following one

public class Person {

    private String name;
    private Integer age;

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

}

And your MultiActionController

import static org.springframework.validation.ValidationUtils.*;

@Component
public class PersonController extends MultiActionController {

    public PersonController() {
        setMethodNameResolver(new InternalPathMethodNameResolver());

        setValidators(new Validator[] {new Validator() {
            public boolean supports(Class clazz) {
                return clazz.isAssignableFrom(Person.class);
            }

            public void validate(Object command, Errors errors) {
                rejectIfEmpty(errors, "age", "", "Age is required");
                rejectIfEmptyOrWhitespace(errors, "name", "", "Name is required");
            }

        }});
    }

    public ModelAndView add(HttpServletRequest request, HttpServletResponse response, Person person) throws Exception {
        // do something (save our Person object, for instance)

        return new ModelAndView();
    }

}

MultiActionController defines a property called validators where you should provide any Validator used by your MultiActionController. Here you can see a piece of code which is responsible for validating your Command object inside MultiActionController

ServletRequestDataBinder binder = ...

if (this.validators != null) 
    for (int i = 0; i < this.validators.length; i++) {
        if (this.validators[i].supports(command.getClass())) {
    ValidationUtils.invokeValidator(this.validators[i], command, binder.getBindingResult());
        }
    }
}

/**
  * Notice closeNoCatch method
  */
binder.closeNoCatch();

closeNoCatch method says

Treats errors as fatal

So if your Validator returns any Error, closeNoCatch will throw a ServletRequestBindingException. But, you can catch it inside your MultiActionController method, as follows

public ModelAndView hanldeBindException(HttpServletRequest request, HttpServletResponse response, ServletRequestBindingException bindingException) {
    // do what you want right here

    BindException bindException = (BindException) bindingException.getRootCause();

    return new ModelAndView("personValidatorView").addAllObjects(bindException.getModel());
}

In order to test, let's do the following one

@Test
public void failureValidation() throws Exception {
    MockHttpServletRequest request = new MockHttpServletRequest();
    request.setMethod("POST");
    request.setRequestURI("http://127.0.0.1:8080/myContext/person/add.html");

    /**
     * Empty values
     */
    request.addParameter("name", "");
    request.addParameter("age", "");

    PersonController personController = new PersonController();

    ModelAndView mav = personController.handleRequest(request, new MockHttpServletResponse());

    BindingResult bindingResult = (BindingResult) mav.getModel().get(BindingResult.MODEL_KEY_PREFIX + "command");

    /**
     * Our Validator rejected 2 Error
     */
    assertTrue(bindingResult.getErrorCount() == 2);
    for (Object object : bindingResult.getAllErrors()) {
        if(object instanceof FieldError) {
            FieldError fieldError = (FieldError) object;

            System.out.println(fieldError.getField());
        }
    }
}