Conditional Checks in Spring

Question

I have a form containing several radio and check-boxes buttons. Whenever a user selects / deselects a radio button or check-box , several other input fields are turned on / off.
I want to add validation only for fields that are included when the user submits the form . Fields that are disabled during presentation should not be considered for validation.

I do not want to add this to client side validation. Is there a better / simple way to implement conditional validation in Spring 3.0 instead of adding multiple ifs to validator?

Thanks!

Answer 1

When fields are disabled, they are passed to the controller as null . I would like to add a check that will allow either null ie to disable the field, or the not blank field, but the included but empty field.
So I created a custom NotBlankOrNull annotation that will allow null and non-empty lines to also take care of empty spaces.
Here is my annotation

 @Documented @Constraint(validatedBy = { NotBlankOrNullValidator.class }) @Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER }) @Retention(RUNTIME) public @interface NotBlankOrNull { String message() default "{org.hibernate.validator.constraints.NotBlankOrNull.message}"; Class<?>[] groups() default { }; Class<? extends Payload>[] payload() default { }; } 

Validator class

 public class NotBlankOrNullValidator implements ConstraintValidator<NotBlankOrNull, String> { public boolean isValid(String s, ConstraintValidatorContext constraintValidatorContext) { if ( s == null ) { return true; } return s.trim().length() > 0; } @Override public void initialize(NotBlankOrNull constraint) { } } 

I also updated more details about my site .

Answer 2

If you use JSR 303 Bean validation, you can use groups to do this.

Suppose you have this user input containing two sections. Two boolean values ​​indicating whether partitions are enabled or disabled. (Of course, you can use more useful annotations than @NotNull )

 public class UserInput { boolean sectionAEnabled; boolean sectionBEnabled; @NotNull(groups=SectionA.class) String someSectionAInput; @NotNull(groups=SectionA.class) String someOtherSectionAInput; @NotNull(groups=SectionB.class) String someSectionBInput; Getter and Setter } 

You need two interfaces for groups. They work only as a marker.

 public interface SectionA{} public interface SectionB{} 

Since Spring 3.1, you can use the Spring @Validated annotation (instead of @Validate ) in your controller method to trigger validation:

 @RequestMapping... public void controllerMethod( @Validated({SectionGroupA.class}) UserInput userInput, BindingResult binding, ...){...} 

Prior to Spring 3.1, it was not possible to specify the verification group that should be used for verification (since @Validated does not exist and @Validate does not have a group attribute), so you need to start the verification using manually written code. This is an example of how to initiate a check based on the witch partition included in Spring 3.0.

 @RequestMapping... public void controllerMethod(UserInput userInput,...){ ValidatorFactory factory = Validation.buildDefaultValidatorFactory(); Validator validator = factory.getValidator(); List<Class<?>> groups = new ArrayList<Class<?>>(); groups.add(javax.validation.groups.Default.class); //Always validate default if (userInput.isSectionAEnabled) { groups.add(SectionA.class); } if (userInput.isSectionBEnabled) { groups.add(SectionB.class); } Set<ConstraintViolation<UserInput>> validationResult = validator.validate(userInput, groups.toArray(new Class[0])); if(validationResult.isEmpty()) { ... } else { ... } } 

(BTW: for Spring 3.0, you can also let Spring introduce a validator:

 @Inject javax.validation.Validator validator <mvc:annotation-driven validator="validator"/> <bean id="validator" class="org.springframework.validation.beanvalidation.LocalValidatorFactoryBean"> <property name="validationMessageSource" ref="messageSource" /> </bean> 

)