Question

let’s assume we have a signup form. When some input of the form is changed, I want to validate its value on the fly by using the ajax call to the server. Is there a chance to validate only some particular property of the bean by using the JSR 303 validation?

The signup form handler validates the received bean just fine, but I want to find out the way to check the property before submit the whole bean.

The straight forward approach is just to create a server-side method to receive the property name and value and based on the name check the value, but I hope there is a way to use already defined constraints for the bean.

For example, the user entered the email address and moved forward to the next property. The client makes a call and the server method checks if the provided email is already exist. If so, it returns an error and I do show it up on the client side. I believe it may make the signup process more flexible and user friendly

Any comments are really appreciated.

Answer 1

The jsr-303 Validator does have a method right on it to validate just one property:

<T> java.util.Set<ConstraintViolation<T>> validateProperty(T object,
                                                           java.lang.String propertyName,
                                                           java.lang.Class<?>... groups)

You just need to inject the validator so that you can use it directly, rather than relying on Spring to call it automatically via putting @Valid on a method parameter.