Symfony2/Doctrine - validation constraint which requires access to a database

问题

I have an entity ArticlePattern, which has a property pattern (string). I need to access the database to check if pattern is correct. So I would like to define a method ArticlePattern::isPatternValid() and add a constraint (using Doctrine's annotation) which would check if isPatternValid is true during validation by Validator object.

From what I have read here and there it is not a good idea, to make an entity depended on service container, which mean I cannot access the doctrine service from inside ArticlePattern::isPatternValid().

So how can I make a custom validation constraint which need an access to the database? How do you deal with such situations which I think is very common seeing so many questions about accessing a service container from an entity class.

EDIT:

Ok, thanks guys, so the answer is a Custom Validation Constraint

回答1:

A validator object can be:

• A simple object, that has no connection to the framework environment at all.
• A service (in the context of dependency injection container) which could do absolutley anything as long as it impements Symfony\Component\Validator\ConstraintValidatorInterface

So what do you have to do?

1. Define a simple constraint
2. Override validatedBy() method to return validator "name" (return 'my_validator';)

3. Define a simple service in DIC:

   <service id="project.validator.my" class="Project\Constraints\MyValidator">
       <!-- service definition here -->
   
       <!-- the service has to be tagged -->
       <tag name="validator.constraint_validator" alias="my_validator" />
   </service>
   

---

EDIT

You've asked about multiple properties validation. In such a case you could create a validator that is related to the object rather to the property of the object.

1. In your constraint class define the target of that constraint (property / class):

   class MyConstraint ... {
       ...
   
       public function targets() {
           return self::CLASS_CONSTRAINT;
       }
   }
   

2. Annotate validated class instead of property:

   @Assert/MyConstraint(...)
   class MyClass {
       private $firstName;
       private $lastName;
   
       @Assert/Email
       private $email;
   
       ...
   }
   

3. The validator itself looks pretty much the same as in case of validating a property:

   class MyValidator extends ConstraintValidator {
       public function isValid($value, Constraint $constraint) {
           // $value is an object rather a property
       }
   }
   

回答2:

Your constraint should override the base validatedBy() method and return the id of the constraint validator service in your container.

public function validatedBy()
{
    return 'my_pattern_validator';
}

来源：https://stackoverflow.com/questions/8934607/symfony2-doctrine-validation-constraint-which-requires-access-to-a-database