Package com.google.appengine.api.datastore

Class Entity

  • All Implemented Interfaces:
    Serializable, Cloneable
    public final class Entity
extends PropertyContainer
implements Cloneable
    Entity is the fundamental unit of data storage. It has an immutable identifier (contained in the Key) object, a reference to an optional parent Entity, a kind (represented as an arbitrary string), and a set of zero or more typed properties.
    See Also:
    Serialized Form

    • Field Detail

      • KEY_RESERVED_PROPERTY

        public static final String KEY_RESERVED_PROPERTY
        A reserved property name used to refer to the key of the entity. This string can be used for filtering and sorting by the entity key itself.
        See Also:
        Constant Field Values

      • SCATTER_RESERVED_PROPERTY

        public static final String SCATTER_RESERVED_PROPERTY
        A reserved property name used to refer to the scatter property of the entity. Used for finding split points (e.g. for mapping over a kind).
        See Also:
        Constant Field Values

      • VERSION_RESERVED_PROPERTY

        public static final String VERSION_RESERVED_PROPERTY
        A reserved property name used to report an entity group's version.
        See Also:
        Constant Field Values

    • Constructor Detail

      • Entity

        public Entity​(String kind)
        Create a new Entity with the specified kind and no parent Entity. The instantiated Entity will have an incomplete Key when this constructor returns. The Key will remain incomplete until you put the Entity, after which time the Key will have its id set.

      • Entity

        public Entity​(String kind,
              @Nullable Key parent)
        Create a new Entity with the specified kind and parent Entity. The instantiated Entity will have an incomplete Key when this constructor returns. The Key will remain incomplete until you put the Entity, after which time the Key will have its id set.

      • Entity

        public Entity​(String kind,
              String keyName)
        Create a new Entity with the specified kind and key name and no parent Entity. The instantiated Entity will have a complete Key when this constructor returns. The Key's name field will be set to the value of keyName.

        This constructor is syntactic sugar for new Entity(KeyFactory.createKey(kind, keyName)).

      • Entity

        public Entity​(String kind,
              long id)
        Create a new Entity with the specified kind and ID and no parent Entity. The instantiated Entity will have a complete Key when this constructor returns. The Key's id field will be set to the value of id.

        Creating an entity for the purpose of insertion (as opposed to update) with this constructor is discouraged unless the id was obtained from a key returned by a KeyRange obtained from AsyncDatastoreService.allocateIds(String, long) or DatastoreService.allocateIds(String, long) for the same kind.

        This constructor is syntactic sugar for new Entity(KeyFactory.createKey(kind, id)).

      • Entity

        public Entity​(String kind,
              String keyName,
              Key parent)
        Create a new Entity with the specified kind, key name, and parent Entity. The instantiated Entity will have a complete Key when this constructor returns. The Key's name field will be set to the value of keyName.

        This constructor is syntactic sugar for new Entity(KeyFactory.createKey(parent, kind, keyName)).

      • Entity

        public Entity​(String kind,
              long id,
              Key parent)
        Create a new Entity with the specified kind and ID and parent Entity. The instantiated Entity will have a complete Key when this constructor returns. The Key's id field will be set to the value of id.

        Creating an entity for the purpose of insertion (as opposed to update) with this constructor is discouraged unless the id was obtained from a key returned by a KeyRange obtained from AsyncDatastoreService.allocateIds(Key, String, long) or DatastoreService.allocateIds(Key, String, long) for the same parent and kind.

        This constructor is syntactic sugar for new Entity(KeyFactory.createKey(parent, kind, id)).

      • Entity

        public Entity​(Key key)
        Create a new Entity uniquely identified by the provided Key. Creating an entity for the purpose of insertion (as opposed to update) with a key that has its id field set is strongly discouraged unless the key was returned by a KeyRange.
        See Also:
        KeyRange

    • Method Detail

      • equals

        public boolean equals​(@Nullable Object object)
        Two Entity objects are considered equal if they refer to the same entity (i.e. their Key objects match).
        Overrides:
        equals in class Object

      • getKey

        public Key getKey()
        Returns the Key that represents this Entity. If the entity has not yet been saved (e.g. via DatastoreService.put), this Key will not be fully specified and cannot be used for certain operations (like DatastoreService.get). Once the Entity has been saved, its Key will be updated to be fully specified.

      • getKind

        public String getKind()
        Returns a logical type that is associated with this Entity. This is simply a convenience method that forwards to the Key for this Entity.

      • getParent

        public @Nullable Key getParent()
        Get a Key that corresponds to this the parent Entity of this Entity. This is simply a convenience method that forwards to the Key for this Entity.

      • hashCode

        public int hashCode()
        Overrides:
        hashCode in class Object

      • getAppId

        public String getAppId()
        Returns the identifier of the application that owns this Entity. This is simply a convenience method that forwards to the Key for this Entity.

      • getNamespace

        public String getNamespace()
        Returns the namespace of the application/namespace that owns this Entity. This is simply a convenience method that forwards to the Key for this Entity.

      • clone

        public Entity clone()
        Returns a shallow copy of this Entity instance. Collection properties are cloned as an ArrayList, the type returned from the datastore. Instances of mutable datastore types are cloned as well. Instances of all other types are reused.
        Returns:
        a shallow copy of this Entity

      • setPropertiesFrom

        public void setPropertiesFrom​(Entity src)