动态创建主义（伪）实体？

Question

I've been thrown a 'can it be done in Doctrine' type question by my supervisor, and while I've been able to do some of it with external 'Mapper' objects, I'm wondering if there might be any way to fake-out the ORM to do it within Doctrine itself.

Essentially, the thing we are interested in doing is cutting down database clutter. We have a number of tables containing distinct properties or item sets in various categories and then a whole bunch of link-tables tying them to other properties or item sets. For example

We have a couple of tables such as 'Materials' and 'PaperTypes' which describe various Material and Paper options for our products. We then group these into 'MaterialCollections' and 'PaperFamilies' respectively. Then there has to be a one-to-many link table between MaterialCollection/Materials and PaperFamilies/PaperTypes respectively. Repeat these types of relationships a couple dozen more times and you see where our DB is starting to clutter up.

The link tables themselves are nothing more than a number of entries including multiple records with the PrimaryId from the parent table (collections/families) and unique-per-parent PrimaryId's from the sub-table (materials/papertypes). Link tables could be named something like MaterialCollectionsMaterials and PaperFamilyPaperTypes for example.

The idea was to get rid of this slew of link tables by using an abstract 3-table structure as follows:

Lists (consisting of a unique ListId, a ListName and a TypeId) Types (consisting of a unique TypeId, a TypeName and an EntityName) ListXref (consisting of ListIds and memberId which points to the primaryId from the Entity designated in the list type)

Multiple lists can exist for a given type, but the Xref pairs are unique. Different Types can also point to the same Entity. (eg there may be more than one type of Material list defined)

The 'ListName' would be the equivalent of the parent TableNames above and would allow for eliminating two of the tables in those relationships. So the records in 'MaterialCollections' would now instead be records in the List table of TypeName "MaterialCollection". The records that would have been in a link table (such as MaterialCollectionsMaterials) would now instead be pointed to from ListXRef.

As stated, I've gotten a basic mapper to make this work for rather basic list creation. But what I'm wondering is if there is any way to create Entities or things that behave like Doctrine Entities to establish the abstract relationships between a given list/listtype and the table referenced by EntityName and the corresponding memberIds?

In other words, it would be really nice if I had some means by which I could produce something that had the bulk of functionality of a Doctrine Entity which could be retrieved from the Service Manager or something like it that would behave (have similar properties/functions) like a Doctrine Entity.

I tried adding a wrapper object in the Entity tree that my mappers could try to retrieve which was basically an inherited version of the Xref entity with a few alias functions, but it can't be retrieved with the Entity manager.

Any help is appreciated.

PS While it is not a priority at the moment, longer term I also want to really throw a wrench into the works by trying to have some lists be capable of pointing back to the records produced by other lists. So, for example, a List "ProductXMaterials" of type "ProductMaterials" might point to some but not all results of "MaterialCollections". But I'll worry about this one later.

Answer 1

Well, Doctrine can't generate "pseudo entity classes" but you can.

First you need to hook into the Doctrine "loadClassMetadata" event. Inside, you generate your entity classes and configuration from code on the fly and dump them into a specified directory (in the cache for example) maintaining the doctrine convention naming but with a custom namespace. For example : "AutoGeneratedNamespace\\Entities"

So let's say you need to have a dynamic entity generated for an entity with name: "TmpUser", and you're using "yml" instead of annotations

<?php
namespace Example;

use Doctrine\ORM\Event\LoadClassMetadataEventArgs;

class DoctrineEventListener
{
    /**
     * Invoked on Doctrine loadClassMetadata event
     *
     * @var Doctrine\ORM\Event\LoadClassMetadataEventArgs
     **/
    public function loadClassMetadata(LoadClassMetadataEventArgs $args)
    {
        $em             = $args->getEntityManager();
        $metadata       = $args->getClassMetadata();
        $factory        = $em->getMetadataFactory();
        $name           = 'AutoGeneratedNamespace\Entities\TmpUser';
        $tmpDirectory   = '/path/to/cache/generated-classes';

        // current class metadata is the same as the one we need. this means we already generated it
        if($metadata->getName() == $name || $factory->hasClassMetadata($name)) {
            return;
        }
        /** 
         Generate your class here and dump it into the cache directory with the name: TmpUser.php
         (If you're using "yml" instead of annotations also create the TmpUser.orm.yml configuration and dump it in the same directory)
        **/

        // create a metadata for the newly created class
        $metadata = $factory->newClassMetadataInstance($name);

        // Register metadata so doctrine knows about it
        $factory->setMetadataFor($name, $metadata);
    }

}

Finally, you tell Doctrine to look for entities inside the cache directory as well using the configuration: (This is taken from the Symfony documentation so if you're not using Symfony it may vary a bit but you can find the precise configuration in the Doctrine docs)

doctrine:
    orm:
        mappings:
            MyGeneratedEntitiesUniqueMappingsKey:
                type: yml
                dir: '/path/to/cache/generated-classes'
                is_bundle: false
                prefix: "AutoGeneratedNamespace\Entities"
                alias: GeneratedEntities