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

   1 package com.google.appengine.api.datastore;
   2
   3 import static com.google.common.base.Preconditions.checkArgument;
   4
   5 import com.google.apphosting.datastore.EntityStorage.CacheValue;
   6 import com.google.apphosting.datastore.EntityStorage.CacheValue.State;
   7 import com.google.apphosting.datastore.EntityStorage.VersionedEntity;
   8 import com.google.storage.onestore.v3.OnestoreEntity.EntityProto;
   9
  10 /**
  11  * Utility methods for the {@link CacheValue} protocol buffer object.
  12  *
  13  */
  14 final class CacheValueUtil {
  15
  16   /**
  17    * Creates a {@link CacheValue} object.
  18    *
  19    * @param state the state of the cache value.
  20    * @param entity the entity to store in the cache value.
  21    * @return a {@code CacheValue} object for the specified {@code state} and {@code entity}.
  22    * @throws IllegalArgumentException if a non-null {@code entity} is specified with
  23    *     a {@code state} other than {@link State#ENTITY}.
  24    */
  25   public static CacheValue createCacheValue(State state, EntityProto entity) {
  26     if (state == State.ENTITY) {
  27       CacheValue cacheValue = new CacheValue();
  28       if (entity != null) {
  29         VersionedEntity versionedEntity = new VersionedEntity();
  30         versionedEntity.setV3Entity(entity);
  31         cacheValue.setEntity(versionedEntity);
  32       }
  33       return cacheValue;
  34     } else {
  35       checkArgument(entity == null, "An entity can only be specified with state " + State.ENTITY);
  36       CacheValue cacheValue = new CacheValue();
  37       cacheValue.setState(state);
  38       return cacheValue;
  39     }
  40   }
  41
  42   /**
  43    * @return {@code true} if the {@code state} is used to demarcate datastore operations.
  44    */
  45   public static boolean isDatastoreOpState(State state) {
  46     return (state == State.READ_IN_PROGRESS) || (state == State.MUTATION_IN_PROGRESS);
  47   }
  48
  49   private CacheValueUtil() {
  50   }
  51 }