@AssociationOverride and @AttributeOverride in new

问题:

As per title, what's the purpose of the new annotation @AssociationOverride and @AttributeOverride?

The only thing I can find on Doctrine website is:

@AssociationOverride and @AttributeOverride (useful for Trait and MappedSuperclass)

回答1:

By looking at the code in the commit, we can see that it is used to override a field mapping already defined in a mapped superclass / trait.

The tests included in the commit demonstrate this behaviour:

Mapped superclass

/** 
 * @MappedSuperclass
 */
class User
{
    /**
     * @Id
     * @GeneratedValue
     * @Column(type="integer", name="user_id", length=150)
     */
    protected $id;

    /**
     * @Column(name="user_name", nullable=true, unique=false, length=250)   
     */
    protected $name;

    /**
     * @var ArrayCollection
     *
     * @ManyToMany(targetEntity="Group", inversedBy="users", cascade={"persist", "merge", "detach"})
     * @JoinTable(name="users_groups",
     *  joinColumns={@JoinColumn(name="user_id", referencedColumnName="id")},
     *  inverseJoinColumns={@JoinColumn(name="group_id", referencedColumnName="id")}
     * )
     */
    protected $groups;

    /**
     * @var Address
     *
     * @ManyToOne(targetEntity="Address", cascade={"persist", "merge"})
     * @JoinColumn(name="address_id", referencedColumnName="id")
     */ 
    protected $address;

    ...
}

Subclass using @AssociationOverride

/*  
 * @Entity
 * @AssociationOverrides({
 *      @AssociationOverride(name="groups",
 *          joinTable=@JoinTable(
 *              name="users_admingroups",
 *              joinColumns=@JoinColumn(name="adminuser_id"),
 *              inverseJoinColumns=@JoinColumn(name="admingroup_id")
 *          )
 *      ),
 *      @AssociationOverride(name="address",
 *          joinColumns=@JoinColumn(
 *              name="adminaddress_id", referencedColumnName="id"
 *          )
 *      )   
 * })
 */
class Admin extends User
{
    ...
}

Subclass using @AttributeOverride

/**
 * @Entity
 * @AttributeOverrides({
 *      @AttributeOverride(name="id",
 *          column=@Column(
 *              name     = "guest_id",
 *              type     = "integer",
 *              length   = 140
 *          )
 *      ),
 *      @AttributeOverride(name="name",
 *          column=@Column(
 *              name     = "guest_name",
 *              nullable = false,
 *              unique   = true,
 *              length   = 240
 *          )
 *      )   
 * })
 */
class Guest extends User
{
    ...
}