Sometimes it may be needed to use manual validation in Spring MVC @Controller. This is very simple with Spring’s org.springframework.validation.ValidationUtils class. Learn how to invoke a validator in two different scenarios.
Scenario 1 – invoke validation
In this scenario, I have a user form with username field. Username field is validated with custom validator in order to verify the existance in e.g. database.
1 2 3 4 5 6 | public class User { @UserExists private String username;} |
In controller class I have a method that handles POST method of that object:
01 02 03 04 05 06 07 08 09 10 11 12 13 14 | @Autowiredprivate org.springframework.validation.Validator validator;@RequestMapping(value = "/user", method = RequestMethod.POST)public String validate(@ModelAttribute User user, Errors errors) { ValidationUtils.invokeValidator(validator, user, errors); if (errors.hasErrors()) { // error, show errors to the user } // success, form is valid!} |
org.springframework.validation.ValidationUtils is a class for invoking a org.springframework.validation.Validator.
Please note that user parameter is followed by org.springframework.validation.Errors object. Spring initializes this object but it is empty and can be be passed to a invokeValidator method.
Scenario 2 – invoke validation with hints
In this scenario, user form gets a bit more complicated:
01 02 03 04 05 06 07 08 09 10 11 12 13 14 | @GroupSequence(value = {ValidationOrder.First.class, ValidationOrder.Second.class})interface ValidationOrder { interface First {} interface Second {}}public class User { @UserExists(groups = ValidationOrder.First.class) @UserIsEntitledToDiscount(groups = ValidationOrder.Second.class) private String username;} |
Thanks to @GroupSequence I could decide about the order of validation. To trigger validation I need to pass an additional argument to invokeValidator method so the groups are correctly used:
1 | ValidationUtils.invokeValidator(validator, user, errors, ValidationOrder.class); |
Source code
The source code contains all three approaches, so that you can quickly compare them: https://github.com/kolorobot/spring-mvc-beanvalidation11-demo
| Reference: | Spring MVC: Trgger manual validation of a form object from our JCG partner Rafal Borowiec at the Codeleak.pl blog. |
