java/src/main/com/google/appengine/api/datastore/Projection.java

   1 // Copyright 2012 Google Inc. All Rights Reserved.
   2
   3 package com.google.appengine.api.datastore;
   4
   5 import java.io.Serializable;
   6 import java.util.Map;
   7
   8 /**
   9  * A query projection.
  10  *
  11  * @see Query#getProjections()
  12  */
  13 public abstract class Projection implements Serializable {
  14
  15   Projection() {}
  16
  17   /**
  18    * Returns the name of the property this projection populates.
  19    */
  20   public abstract String getName();
  21
  22   /**
  23    * Returns the name of the original datastore property.
  24    */
  25   abstract String getPropertyName();
  26
  27   /**
  28    * Generates the projection value from the given entity values.
  29    */
  30   abstract Object getValue(Map<String, Object> values);
  31 }