How to do Spring MVC validation

First, Validation is a controller unit and it can com in three ways:

First Approach:

Use JSR-303 annotations

Requirement: Spring 3.x

example:

public class MyClass {

         @NotNull

         private String name;

         

         @NotEmpty @Email  //需要Hibernate Validator

         private String email;

         @NotNull @Min(18) @Max(65)

      private Integer age;

}

In spring controller method add @Valid before your classes/parameter

example:

@RequestMapping("myPath")

public void handleRequest(Model model, 

                   @Valid @ModelAttribute("myClass") MyClass myClass, 

                   BindingResult result) {

           if(result.hasErrors()) { 

                   // validation fail, do something

           }

           //validation success, other code

}

Pros : fast and easy, validate object according to annotation inside MyClass
Cons: Can only used on binding object, we can not use it on primitive data type.

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Second Approach:

Use A separate Validator component or service (@Component/@Service)

You have to create : a Validator class implements springframework.validation.Validator

In controller

@Autowired

private MyValidator myValidator;

@Autowired

private OtherValidator otherValidator;

example:

@RequestMapping("myPath")

public void handleRequest(Model model, 

                   @ModelAttribute("myClass") MyClass myClass, 

                   BindingResult result) {

           myValidator.validate(myClass, result);

           if(result.hasErrors()) { 

                   // validation fail, do something

           }

           otherValidator.validate(myParam, result);

           if(result.hasErrors()) { 

                   // validation fail, do something

           }

           //validation success, other code

}

Pros: Handle complex validation, can bind with other component/service in validator.

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Third Approach by creating a BindingResult in Controller:
If you can not get a BindingResult (Not using a form object), the binding result can be accessed by DataBinder class :

example (Tested) :

In your mapping function :
        DataBinder binder = new DataBinder(MyObject);
        binder.setValidator(MyObjectValidator);
        binder.validate();
        BindingResult results = binder.getBindingResult();
        if(results.hasErrors()) {
                //handle your error
        }else {
                //do your work
        }

Pros: Free from the BindingResult restrictions.
Cons: Not a neat coding.

詳細資料及來源:

https://stackoverflow.com/questions/12146298/spring-mvc-how-to-perform-validation/12149331#12149331?newreg=939c481aded644119cfdcf43a48718bb

後感:

Spring validation 也很有MVC的特色, 分門別類很清楚, 可惜只可以用係request object上, 如果只得一個primitive要拎就唯有form object, 或者用DataBinder拎BindingResult