Package com.google.appengine.api.datastore

Class Entities

java.lang.Object
com.google.appengine.api.datastore.Entities
public final class Entities extends Object
Utility functions and constants for entities.

  • Field Details

    • KIND_METADATA_KIND

      public static final String KIND_METADATA_KIND
      A metadata kind that can be used to query for kinds that exist in the datastore.
      See Also:

    • PROPERTY_METADATA_KIND

      public static final String PROPERTY_METADATA_KIND
      A metadata kind that can be used to query for properties that exist in the datastore.
      See Also:

    • NAMESPACE_METADATA_KIND

      public static final String NAMESPACE_METADATA_KIND
      A metadata kind that can be used to query for namespaces that exist in the datastore.
      See Also:

    • NAMESPACE_METADATA_EMPTY_ID

      public static final long NAMESPACE_METADATA_EMPTY_ID
      The numeric ID for __namespace__ keys representing the empty namespace.
      See Also:

    • ENTITY_GROUP_METADATA_KIND

      public static final String ENTITY_GROUP_METADATA_KIND
      A metadata kind that can be used to get information about entity groups. The metadata for the entity group with root entity key R is fetched using a DatastoreService.get(com.google.appengine.api.datastore.Key) call on key KeyFactory.createKey(R, ENTITY_GROUP_METADATA_KIND, ENTITY_GROUP_METADATA_ID).

      The resulting entity has a Entity.VERSION_RESERVED_PROPERTY numeric property whose value is guaranteed to increase on every change to the entity group. This value may also occasionally increase without any user-visible change to the entity group.

      See Also:

    • ENTITY_GROUP_METADATA_ID

      public static final long ENTITY_GROUP_METADATA_ID
      ID for __entity_group__ entities.
      See Also:

  • Constructor Details

    • Entities

      public Entities()

  • Method Details

    • createKindKey

      public static Key createKindKey(String kind)
      Create a __kind__ key for kind.
      Parameters:
      kind - Kind to create key for.
      Returns:
      __kind__ key.

    • createPropertyKey

      public static Key createPropertyKey(String kind, String property)
      Create a __property__ key for property of kind.
      Parameters:
      kind - Kind to create key for.
      property - Property to create key for.
      Returns:
      __property__ key.

    • createNamespaceKey

      public static Key createNamespaceKey(String namespace)
      Create a __namespace__ key for namespace.
      Parameters:
      namespace - Namespace to create key for.
      Returns:
      __namespace__ key.

    • getNamespaceFromNamespaceKey

      public static @Nullable String getNamespaceFromNamespaceKey(Key namespaceKey)
      Extract the namespace name from a __namespace__ key.
      Parameters:
      namespaceKey - Key to extract namespace from.
      Returns:
      The namespace name.

    • createEntityGroupKey

      public static Key createEntityGroupKey(Key key)
      Create an __entity_group__ key for the entity group containing key.
      Parameters:
      key - Key of any entity in the entity group.
      Returns:
      __entity_group__ key.

    • getVersionProperty

      public static long getVersionProperty(Entity entity)
      Get the value of the __version__ property from entity.
      Parameters:
      entity - Entity to fetch __version__ from (must have a numeric __version__ property).
      Returns:
      __version__ property value.