com.google.appengine.api.datastore

## Class Entities

- java.lang.Object
- - com.google.appengine.api.datastore.Entities

-     public final class Entities
      extends java.lang.Object

  Utility functions and constants for entities.

- - ### Field Summary

    Fields
    Modifier and Type | Field and Description
    --- | ---
    `static long` | `ENTITY_GROUP_METADATA_ID` ID for __entity_group__ entities.
    `static java.lang.String` | `ENTITY_GROUP_METADATA_KIND` A metadata kind that can be used to get information about entity groups.
    `static java.lang.String` | `KIND_METADATA_KIND` A metadata kind that can be used to query for kinds that exist in the datastore.
    `static long` | `NAMESPACE_METADATA_EMPTY_ID` The numeric ID for __namespace__ keys representing the empty namespace.
    `static java.lang.String` | `NAMESPACE_METADATA_KIND` A metadata kind that can be used to query for namespaces that exist in the datastore.
    `static java.lang.String` | `PROPERTY_METADATA_KIND` A metadata kind that can be used to query for properties that exist in the datastore.

  - ### Constructor Summary

    Constructors
    Constructor and Description
    `Entities()`

  - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `static Key` | `createEntityGroupKey(Key key)` Create an __entity_group__ key for the entity group containing `key`.
    `static Key` | `createKindKey(java.lang.String kind)` Create a __kind__ key for `kind`.
    `static Key` | `createNamespaceKey(java.lang.String namespace)` Create a __namespace__ key for `namespace`.
    `static Key` | `createPropertyKey(java.lang.String kind, java.lang.String property)` Create a __property__ key for `property` of `kind`.
    `static java.lang.String` | `getNamespaceFromNamespaceKey(Key namespaceKey)` Extract the namespace name from a __namespace__ key.
    `static long` | `getVersionProperty(Entity entity)` Get the value of the __version__ property from `entity`.

    - ### Methods inherited from class java.lang.Object

      `equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- - ### Field Detail

    - #### KIND_METADATA_KIND

          public static final java.lang.String KIND_METADATA_KIND

      A metadata kind that can be used to query for kinds that exist in the datastore.
      See Also:
        Constant Field Values

    - #### PROPERTY_METADATA_KIND

          public static final java.lang.String PROPERTY_METADATA_KIND

      A metadata kind that can be used to query for properties that exist in the datastore.
      See Also:
        Constant Field Values

    - #### NAMESPACE_METADATA_KIND

          public static final java.lang.String NAMESPACE_METADATA_KIND

      A metadata kind that can be used to query for namespaces that exist in the datastore.
      See Also:
        Constant Field Values

    - #### NAMESPACE_METADATA_EMPTY_ID

          public static final long NAMESPACE_METADATA_EMPTY_ID

      The numeric ID for __namespace__ keys representing the empty namespace.
      See Also:
        Constant Field Values

    - #### ENTITY_GROUP_METADATA_KIND

          public static final java.lang.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:
        Constant Field Values

    - #### ENTITY_GROUP_METADATA_ID

          public static final long ENTITY_GROUP_METADATA_ID

      ID for __entity_group__ entities.
      See Also:
        `ENTITY_GROUP_METADATA_KIND`, Constant Field Values

  - ### Constructor Detail

    - #### Entities

          public Entities()

  - ### Method Detail

    - #### createKindKey

          public static Key createKindKey(java.lang.String kind)

      Create a __kind__ key for `kind`.
      Parameters:
        `kind` - Kind to create key for.
      Returns:
        __kind__ key.

    - #### createPropertyKey

          public static Key createPropertyKey(java.lang.String kind,
                              java.lang.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(java.lang.String namespace)

      Create a __namespace__ key for `namespace`.
      Parameters:
        `namespace` - Namespace to create key for.
      Returns:
        __namespace__ key.

    - #### getNamespaceFromNamespaceKey

          public static java.lang.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.