KeyFactory (Google App Engine API for Java)

com.google.appengine.api.datastore

Class KeyFactory

  • java.lang.Object
    • com.google.appengine.api.datastore.KeyFactory


  • public class KeyFactory
    extends java.lang.Object
    This class enables direct creation of Key objects, both in the root entity group (no parent) and as the child of a given parent. Keys can also be created indirectly by putting named Entities into the datastore, which will allocate a new key. See Entity.Entity(String, String) for details.

    This class also has methods for encoding and decoding Key objects to and from strings. Clients should not make any assumptions about the encoding format, except that it is a websafe string that does not need to be quoted when used in HTML or in URLs.

    See Also:
    Entity
    • Method Detail

      • createKey

        public static Key createKey(java.lang.String kind,
                                    long id)
        Creates a new Key having no parent from its kind and ID.
        Parameters:
        kind - the kind of the key to create
        id - the numeric identifier of the key in kind, unique across all root entities of this kind, must not be zero
      • createKey

        public static Key createKey(Key parent,
                                    java.lang.String kind,
                                    long id)
        Creates a new Key with the provided parent from its kind and ID.
        Parameters:
        parent - the parent of the key to create, can be null
        kind - the kind of the key to create
        id - the numeric identifier of the key in kind, unique across all entities of this kind with the same parent, must not be zero
      • createKey

        public static Key createKey(java.lang.String kind,
                                    java.lang.String name)
        Creates a new Key having no parent from its kind and name.
        Parameters:
        kind - the kind of the key to create
        name - the name of the key in kind, as an arbitrary string unique across all root entities of this kind
      • createKey

        public static Key createKey(Key parent,
                                    java.lang.String kind,
                                    java.lang.String name)
        Creates a new Key with the provided parent from its kind and name.
        Parameters:
        parent - the parent of the key to create, can be null
        kind - the kind of the key to create
        name - the name of the key in kind, as an arbitrary string unique across all entities of this kind with the same parent
      • createKeyString

        public static java.lang.String createKeyString(java.lang.String kind,
                                                       long id)
        Shorthand for invoking keyToString(Key) on the result of createKey(String, long)
        Parameters:
        kind - the kind of the key to create
        id - the numeric identifier of the key in kind, unique across all root entities of this kind, must not be zero
        Returns:
        A websafe String representation of the Key that was created
      • createKeyString

        public static java.lang.String createKeyString(Key parent,
                                                       java.lang.String kind,
                                                       long id)
        Shorthand for invoking keyToString(Key) on the result of createKey(Key, String, long)
        Parameters:
        parent - the parent of the key to create, can be null.
        kind - the kind of the key to create
        id - the numeric identifier of the key in kind, unique across entities of this kind with the same parent, must not be zero
        Returns:
        A websafe String representation of the Key that was created
      • createKeyString

        public static java.lang.String createKeyString(java.lang.String kind,
                                                       java.lang.String name)
        Shorthand for invoking keyToString(Key) on the result of createKey(String, String)
        Parameters:
        kind - the kind of the key to create
        name - the name of the key in kind, as an arbitrary string unique across root entities of this kind
        Returns:
        A websafe String representation of the Key that was created
      • createKeyString

        public static java.lang.String createKeyString(Key parent,
                                                       java.lang.String kind,
                                                       java.lang.String name)
        Shorthand for invoking keyToString(Key) on the result of createKey(Key, String, String)
        Parameters:
        parent - the parent of the key to create, can be null.
        kind - the kind of the key to create
        name - the name of the key in kind, as an arbitrary string unique across entities of this kind with the same parent
        Returns:
        A websafe String representation of the Key that was created
      • keyToString

        public static java.lang.String keyToString(Key key)
        Converts a Key into a websafe string. For example, this string can safely be used as an URL parameter embedded in a HTML document. Note that key.equals(KeyFactory.stringToKey(KeyFactory.keyToString(key)) should evaluate to true.
        Parameters:
        key - The Key to convert to a String.
        Returns:
        A websafe String representation of the provided String.
        Throws:
        java.lang.IllegalArgumentException - If the specified Key is incomplete.
      • stringToKey

        public static Key stringToKey(java.lang.String encoded)
        Converts a String-representation of a Key into the Key instance it represents. Note that str.equals(KeyFactory.keyToString(KeyFactory.stringToKey(str)) should evaluate to true for all strings returned by keyToString(com.google.appengine.api.datastore.Key).
        Parameters:
        encoded - The String representation of a Key.
        Returns:
        The Key that the given String represents.
        Throws:
        java.lang.IllegalArgumentException - If the string cannot be parsed.

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