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Spring MVC, Spring Bean Validation Framework and validating confirm password / confirm email fields.

How to write validation like confirm password, confirm email and etc in Spring MVC.
NOTE: To make bean validation to work its nice to read this tutorial: <a href="http://wheelersoftware.com/articles/spring-bean-validation-framework.html"></a>
Today I was busy making some validations and implementations on very common scenario:
change email and password.
So we have a new password AND a new email also for both of them we have a confirm email/password field. And we want to validate everything nicely and to show to the user the real validation message if there is some error.
So ... I've to use a form which already uses some annotations like @NoBlank and etc I think everyone of you is using annotations framework if you don't use it SHAME ON YOU !:)

Anyway so I've added some fields to existing form bean:
private String newPassword;
private String confirmNewPassword;
private String newEmail;
private String confirmNewEmail;

Basiclly in my case this is very big form and none of this fields is mendatory so the user can leave all of them blank. My first idea was to add at least Length for the password and Email annotations for the email so I do:
@Length(min=6,max=20)
private String newPassword;
private String confirmNewPassword;
@Email
private String newEmail;
private String confirmNewEmail;

Ok but the confirm fields should have the same rules ? Maybe...
The problem that I saw is that length and email by default means NotBlank.
To make email validator to work or length validator they first check is the field blank. In my case I want the blank to be OK.. so I asked god google what to do.
The answer applyIf.
So at the end I get :
@Length(min = 6, max = 20, applyIf = "newPassword is not blank") //cool right ?
private String newPassword;
private String confirmNewPassword;
@Email(applyIf = "newEmail is not blank") //cool right ?
private String newEmail;
private String confirmNewEmail;

Cool right ? yep it is cool. but let me add the validation for confirmNewPassword and confirmNewEmail.
@Length(min = 6, max = 20, applyIf = "newPassword is not blank")
private String newPassword;
@NotBlank(applyIf = "newPassword is not blank")
private String confirmNewPassword;

@Email(applyIf = "newEmail is not blank")
private String newEmail;
@NotBlank(applyIf = "newEmail is not blank")
@Email(applyIf = "newEmail is not blank")
private String confirmNewEmail;

Nice.. so I have validation on new* fields only if they are not blank. Also I have a validation on the confirm fields only if again new* fields are not blank.
Cool... what left ? ahh the most hard part to check is the confirmpassword the same as the newPassword and is the confirmEmail same as the newEmail.
the first idea ofcourse is to write a custom validator.
So I write this :
class NewPassAndEmailValidator implements Validator {
    @Override
    public boolean supports(Class<?> clazz) {
        return PersonalDetailsFormBean.class.equals(clazz);
    }

    @Override
    public void validate(Object obj, Errors errors) {
        PersonalDetailsFormBean personalDetailsFormBean = (PersonalDetailsFormBean) obj;
        if (personalDetailsFormBean.getNewPassword() != null
                && !personalDetailsFormBean.getNewPassword().equals("")) {
            if (!personalDetailsFormBean.getNewPassword().equals(personalDetailsFormBean.getConfirmNewPassword())) {
                errors.rejectValue("confirmNewPassword", "PersonalDetailsFormBean.confirmNewPassword[customvalidator]");
            }
        }
        if (personalDetailsFormBean.getNewEmail() != null && !personalDetailsFormBean.getNewEmail().equals("")) {
            if (!personalDetailsFormBean.getNewEmail().equals(personalDetailsFormBean.getConfirmNewEmail())) {
                errors.rejectValue("confirmNewEmail", "PersonalDetailsFormBean.confirmNewEmail[customvalidator]");
            }
        }
    }

}
and then in the controller submit method.
validator.validate(personalDetailsFormBean, result); //this invokes the annotation based validator.
NewPassAndEmailValidator newPassAndEmailValidator = new NewPassAndEmailValidato();
newPassAndEmailValidator.validate(personalDetailsFormBean, result);

if (result.hasErrors()) {
... return...
}

This .... WORKS FINE. BUT... ah its not cool :( ... I mean even in struts 1 in 2001 we ware having a validation based on expression. AND we have even better way here... Awesome :D
So I've removed this validator... and write only "this":
@Expression(value = "confirmNewPassword = newPassword", applyIf = "newPassword is not blank")
So the final example looks like this:
@Length(min = 6, max = 20, applyIf = "newPassword is not blank")
private String newPassword;
@NotBlank(applyIf = "newPassword is not blank")
@Expression(value = "confirmNewPassword = newPassword", applyIf = "newPassword is not blank")
private String confirmNewPassword;

@Email(applyIf = "newEmail is not blank")
private String newEmail;
@NotBlank(applyIf = "newEmail is not blank")
@Email(applyIf = "newEmail is not blank")
@Expression(value = "confirmNewEmail = newEmail", applyIf = "newEmail is not blank")
private String confirmNewEmail;

:) ok this looks cool :D maybe not so cool than 20+ if statements to checks for null for some of you to but I like this way :))

Comments

Unknown said…
This is exactly what I was looking for. Checking equality of fields using annotations. Great post, thanks.
Reuben said…
Yes, very cool. Thanks for sharing.
Thanks a lot, JOke. The example of @Expression is very useful. I found it nowhere but here.

Kind regards
Vuong
Unknown said…
Awesome Buddy..
thnx a million......

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