NamespaceManager (Google App Engine API for Java)

com.google.appengine.api

Class NamespaceManager

  • java.lang.Object
    • com.google.appengine.api.NamespaceManager


  • public final class NamespaceManager
    extends java.lang.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:
    Multitenancy and the Namespaces Java API. In Google App Engine Developer's Guide.
    • Method Summary

      All Methods Static Methods Concrete Methods 
      Modifier and Type Method and Description
      static java.lang.String get()
      Returns the current namespace setting or null if not set.
      static java.lang.String getGoogleAppsNamespace()
      Returns the Google Apps domain referring this request or otherwise the empty string ("").
      static void set(java.lang.String newNamespace)
      Set the value used to initialize the namespace of namespace-aware services.
      static void validateNamespace(java.lang.String namespace)
      Validate the format of a namespace string.
      • Methods inherited from class java.lang.Object

        equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
    • Method Detail

      • set

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

        public static java.lang.String get()
        Returns the current namespace setting or null 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 java.lang.String getGoogleAppsNamespace()
        Returns the Google Apps domain referring this request or otherwise the empty string ("").
      • validateNamespace

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

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