javax.validation.Validation 多重实例化与重用单个 Validator 实例

Question

我正在使用 javax.validation.Validation 来验证 jpa 实体。我总是针对相同的实体进行验证。

我想知道是对所有验证使用一个 validator 更好，还是每次验证时实例化一个新 validator 更好。

此外，每次我想使用它时实例化一个新的 validator 对我来说在计算方面有多昂贵？

选项 1:为每个验证实例化新的 validator 。

public class Validator
{

    public static void main(String[] args)
    {


        //Validation1
        ValidatorFactory factory = Validation.buildDefaultValidatorFactory();
        Validator validator = factory.getValidator();

        Entity entityToValidate  = new Entity();
        entityToValidate.setEmail("NOT_A_VALID_EMAIL@@@tomanyat.com");
        Set<ConstraintViolation<T>> constraintViolations =             validator.validate(entityToValidate);





        //Validation2 (Note that validator has been created yet a second time !! )
        Validator validator2 = factory.getValidator();

        Entity entityToValidate2  = new Entity();        
         entityToValidate.setEmail("NOT_A_VALID_EMAIL@@@tomanyat.com");

        Set<ConstraintViolation<T>> constraintViolations2 = validator2.validate(entityToValidate);



    }


}

选项 2:所有验证的单个 validator 。

public class Validator
{

    public static void main(String[] args)
    {
        //Validator created only once
        ValidatorFactory factory = Validation.buildDefaultValidatorFactory(); 
        Validator validator = factory.getValidator();


        //Validation #1
        Entity entityToValidate  = new Entity();
        entityToValidate.setEmail("NOT_A_VALID_EMAIL@@@tomanyat.com");

        Set<ConstraintViolation<T>> constraintViolations = validator.validate(entityToValidate);




        //Validation #2     
        Entity entityToValidate2  = new Entity();
        entityToValidate.setEmail("NOT_A_VALID_EMAIL@@@tomanyat.com");


        Set<ConstraintViolation<T>> constraintViolations2 = validator .validate(entityToValidate);



    }


}

Answer 1

请注意 Validator javadoc 的状态

Validates bean instances. Implementations of this interface must be thread-safe.

因此，Validator 不应该真正包含状态，除非该状态也是线程安全的。因此，您不需要创建新的 Validator 实例，只需重复使用同一个实例，显然取决于类型。

As well, how expensive in terms of computation is it for me to instantiate a new validator each time I would like to use it?

这取决于您的 validator 。但是实例化(创建但不初始化对象)本身几乎完全可以忽略不计，尤其是当您考虑 JPA 实现执行的所有处理时。