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

   1 // Copyright 2012 Google Inc. All Rights Reserved.
   2
   3 package com.google.appengine.api.datastore;
   4
   5 import static com.google.common.base.Preconditions.checkArgument;
   6 import static com.google.common.base.Preconditions.checkNotNull;
   7
   8 import java.util.Map;
   9 import java.util.Objects;
  10
  11 /**
  12  * A property projection.
  13  *
  14  * If specified on a query, this will cause the query return the specified property.
  15  *
  16  * @see Query#getProjections()
  17  */
  18 public final class PropertyProjection extends Projection {
  19   private final String propertyName;
  20   private final Class<?> type;
  21
  22   /**
  23    * Constructs a property projection.
  24    *
  25    * If type is specified, {@link RawValue#asType(Class)} will be used to restore
  26    * the original value of the property. Otherwise instances of {@link RawValue}
  27    * will be returned.
  28    *
  29    * @param propertyName The name of the property to project
  30    * @param type The type of values stored in the projected properties or
  31    * {@code null} if the type is not known or variable. If {@code null}, {@link
  32    * RawValue RawValues} are returned.
  33    */
  34   public PropertyProjection(String propertyName, Class<?> type) {
  35     checkArgument(type == null || DataTypeTranslator.getTypeMap().containsKey(type),
  36         "Unsupported type: " + type);
  37     this.propertyName = checkNotNull(propertyName);
  38     this.type = type;
  39   }
  40
  41   @Override
  42   public String getName() {
  43     return propertyName;
  44   }
  45
  46   /**
  47    * Returns the type specified for this projection.
  48    */
  49   public Class<?> getType() {
  50     return type;
  51   }
  52
  53   @Override
  54   String getPropertyName() {
  55     return propertyName;
  56   }
  57
  58   @Override
  59   Object getValue(Map<String, Object> values) {
  60     checkArgument(values.containsKey(propertyName));
  61     Object value = values.get(propertyName);
  62     if (type != null && value != null) {
  63       checkArgument(value instanceof RawValue);
  64       value = ((RawValue) value).asType(type);
  65     }
  66     return value;
  67   }
  68
  69   @Override
  70   public String toString() {
  71     return propertyName;
  72   }
  73
  74   @Override
  75   public int hashCode() {
  76     return Objects.hash(propertyName, type);
  77   }
  78
  79   @Override
  80   public boolean equals(Object obj) {
  81     if (this == obj) return true;
  82     if (obj == null) return false;
  83     if (getClass() != obj.getClass()) return false;
  84     PropertyProjection other = (PropertyProjection) obj;
  85     if (!propertyName.equals(other.propertyName)) return false;
  86     if (type == null) {
  87       if (other.type != null) return false;
  88     } else if (!type.equals(other.type)) return false;
  89     return true;
  90   }
  91 }