Package com.google.appengine.api.datastore

Class KeyFactory

java.lang.Object

com.google.appengine.api.datastore.KeyFactory

public class KeyFactory
extends 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(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

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	KeyFactory.Builder	Helper class that aids in the construction of Keys with ancestors.

Method Summary

Modifier and Type	Method	Description
static Key	createKey(@Nullable Key parent, String kind, long id)	Creates a new Key with the provided parent from its kind and ID.
static Key	createKey(@Nullable Key parent, String kind, String name)	Creates a new Key with the provided parent from its kind and name.
static Key	createKey(String kind, long id)	Creates a new Key having no parent from its kind and ID.
static Key	createKey(String kind, String name)	Creates a new Key having no parent from its kind and name.
static String	createKeyString(@Nullable Key parent, String kind, long id)	Shorthand for invoking keyToString(Key) on the result of createKey(Key, String, long)
static String	createKeyString(@Nullable Key parent, String kind, String name)	Shorthand for invoking keyToString(Key) on the result of createKey(Key, String, String)
static String	createKeyString(String kind, long id)	Shorthand for invoking keyToString(Key) on the result of createKey(String, long)
static String	createKeyString(String kind, String name)	Shorthand for invoking keyToString(Key) on the result of createKey(String, String)
static String	keyToString(Key key)	Converts a Key into a websafe string.
static Key	stringToKey(String encoded)	Converts a String-representation of a Key into the Key instance it represents.

Methods inherited from class java.lang.Object

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

Method Detail

createKey

public static Key createKey(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(@Nullable Key parent,
                            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(String kind,
                            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(@Nullable Key parent,
                            String kind,
                            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 String createKeyString(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 String createKeyString(@Nullable Key parent,
                                     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 String createKeyString(String kind,
                                     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 String createKeyString(@Nullable Key parent,
                                     String kind,
                                     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 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:

IllegalArgumentException - If the specified Key is incomplete.

stringToKey

public static Key stringToKey(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:

IllegalArgumentException - If the string cannot be parsed.