How does Doctrine2 set the Id values

Question

I have a question out of curiosity about the inner workings of Doctrine2. I as a User see a really clean and robust interface, but there must be some heavy magic at work under the hood.

When I generate a simple entity it looks something like this:

class SimpleEntity
{
    /**
     * @ORM\Id
     * @ORM\Column(type="integer")
     * @ORM\GeneratedValue(strategy="AUTO")
     */
    protected $id;

    /**
     * @ORM\Column(type="string")
     */
    protected $title;

    /**
     * Get id
     *
     * @return integer 
     */
    public function getId()
    {
        return $this->id;
    }

    /**
     * Set title
     *
     * @param string $title
     */
    public function setTitle($title)
    {
        $this->title = $title;
    }

    /**
     * Get title
     *
     * @return string 
     */
    public function getTitle()
    {
        return $this->title;
    }
}

As you will notice one thing is conspicuously absent, there is no way to set the id, but nevertheless doctrines factories return entities with set ids. How can that work? I have tried to look through the source, but lost the track somewhere.

How can it be possible to overwrite protected values without being in the class hierarchy?

Maybe there is something about the @ORM annotations. I think this is where the magic happens. — florian
The annotations give doctrine a entry point through reflection but, is reflection capable of setting values? This would even contradict the name... — FloydThreepwood

Phil Phil · Accepted Answer · 2011-11-04T00:10:33

The answer is Reflection. See http://www.doctrine-project.org/docs/orm/2.1/en/tutorials/getting-started-xml-edition.html#a-first-prototype

Without digging into the Doctrine source, I'd say it makes use of ReflectionProperty::setValue()

How does Doctrine2 set the Id values

1 Answers