Package com.google.appengine.api

Class NamespaceManager

java.lang.Object
com.google.appengine.api.NamespaceManager
public final class NamespaceManager extends Object
Provides functions for manipulating the current namespace used for App Engine APIs.

The "current namespace" is the string that is returned by get() and used by a number of APIs including Datatore, Memcache and Task Queue.

When a namespace aware class (e.g., Key, Query and MemcacheService) is constructed, it determines which namespace will be used by calling get() if it is otherwise unspecified. If get() returns null, the current namespace is unset and these APIs will use the empty ("") namespace in its place.

Example: 

 NamespaceManager.set(java.lang.String)("a-namespace");
 MemcacheService memcache = MemcacheServiceFactory.getMemcacheService();
 // Store record in namespace "a-namespace"
 memcache.put("key1", "value1");

 NamespaceManager.set(java.lang.String)("other-namespace");
 // Store record in namespace "other-namespace"
 memcache.put("key2", "value2");

 MemcacheService boundMemcache =
     MemcacheServiceFactory.getMemcacheService("specific-namespace");
 NamespaceManager.set(java.lang.String)("whatever-namespace");
 // The record is still stored in namespace "specific-namespace".
 boundMemcache.put("key3", "value3");

MemcacheService memcache (in the above example) uses the current namespace and key1 will be stored in namespace "a-namespace", while key2 is stored in namespace "other-namespace". It is possible to override the current namespace and store data in specific namespace. In the above example key3 is stored in namespace "specific-namespace".

The Task Queue Queue.add() methods will forward the NamespaceManager settings into the task being added causing the added task to be executed with the same current namespace as the task creator. The exception is that an unset current namespace (i.e. get() returns null) will be forwarded as an empty ("") namespace to the created task's requests.

See Also:

  • Method Details

    • set

      public static void set(String newNamespace)
      Set the value used to initialize the namespace of namespace-aware services.
      Parameters:
      newNamespace - the new namespace.
      Throws:
      IllegalArgumentException - if namespace string is invalid.

    • get

      public static String get()
      Returns the current namespace setting or either null or "" (empty) if not set.

      If the current namespace is unset, callers should assume the use of the "" (empty) namespace in all namespace-aware services.

    • getGoogleAppsNamespace

      public static String getGoogleAppsNamespace()
      Returns the Google Apps domain referring this request or otherwise the empty string ("").

    • validateNamespace

      public static void validateNamespace(String namespace)
      Validate the format of a namespace string.
      Throws:
      IllegalArgumentException - If the format of the namespace string is invalid.