Symfony2 get validation constraints on an entity

问题

Im working on a method to get all validation constraints of an entity (what i am trying to achieve is to return this data in JSON and apply the same constraints on client side using JQuery Validation Plugin), however im having some trouble getting the constraints, Here is my current code:

    $metadata = new \Symfony\Component\Validator\Mapping\ClassMetadata("Namespace\JobBundle\Entity\Job");
    $annotationloader = new AnnotationLoader(new AnnotationReader());
    $annotationloader->loadClassMetadata($metadata);

what i get in $metadata is an empty array for the constraints attribute, the rest ($properties and $members have only the error messages... but not the actual constraints (eg : required, integer...)).

What im a doing wrong?

回答1:

I would probably use the validator service instead of instantiating a new class metadata. You never know if some classes are initialized through the service.

$metadata = $this->container
                 ->get('validator')
                 ->getMetadataFactory()
                 ->getClassMetadata("Name‌​space\JobBundle\Entity\Job");

and $metadata should have the data you are looking for

Symfony 2.3 and above

$metadata = $this->container
                 ->get('validator')
                 ->getMetadataFor("Name‌​space\JobBundle\Entity\Job");

回答2:

private function getValidations()
    {
        $validator=$this->get("validator");
        $metadata=$validator->getMetadataFor(new yourentity());
        $constrainedProperties=$metadata->getConstrainedProperties();
        foreach($constrainedProperties as $constrainedProperty)
        {
            $propertyMetadata=$metadata->getPropertyMetadata($constrainedProperty);
            $constraints=$propertyMetadata[0]->constraints;
            foreach($constraints as $constraint)
            {
                //here you can use $constraint to get the constraint, messages etc that apply to a particular property of your entity
            }
        }
    }

$validator=$this->get("validator");
$metadata=$validator->getMetadataFor(new yourentity());
The object $metadata now contains all the metadata about validations that concerns your specific entity.

来源：https://stackoverflow.com/questions/15482725/symfony2-get-validation-constraints-on-an-entity