java/src/main/com/google/appengine/api/labs/datastore/overlay/NamespacePinnedQueryResultIteratorImpl.java

   1 package com.google.appengine.api.labs.datastore.overlay;
   2
   3 import static com.google.common.base.Preconditions.checkNotNull;
   4
   5 import com.google.appengine.api.datastore.Cursor;
   6 import com.google.appengine.api.datastore.DatastoreService;
   7 import com.google.appengine.api.datastore.Entity;
   8 import com.google.appengine.api.datastore.Index;
   9 import com.google.appengine.api.datastore.QueryResultIterator;
  10 import com.google.common.collect.ImmutableList;
  11
  12 import java.util.List;
  13
  14 /**
  15  * An implementation of {@link QueryResultIterator<Entity>} for use with a namespace-pinned
  16  * {@link DatastoreService}.
  17  *
  18  * <p>We run the query as usual, and then transform any returned entities back to the original
  19  * namespace.
  20  */
  21 final class NamespacePinnedQueryResultIteratorImpl implements QueryResultBatchIterator<Entity> {
  22   private final NamespacePinnedAsyncDatastoreServiceImpl datastore;
  23   private final QueryResultIterator<Entity> iterator;
  24
  25   /**
  26    * Constructs a namespace-pinned {@link QueryResultIterator<Entity>}.
  27    *
  28    * @param datastore the namespace-pinned Datastore
  29    * @param iterator the underlying iterator
  30    */
  31   public NamespacePinnedQueryResultIteratorImpl(NamespacePinnedAsyncDatastoreServiceImpl datastore,
  32       QueryResultIterator<Entity> iterator) {
  33     this.datastore = checkNotNull(datastore);
  34     this.iterator = checkNotNull(iterator);
  35   }
  36
  37   @Override
  38   public boolean hasNext() {
  39     return iterator.hasNext();
  40   }
  41
  42   @Override
  43   public Entity next() {
  44     return datastore.getOriginalNamespaceEntity(iterator.next());
  45   }
  46
  47   @Override
  48   public List<Entity> nextList(int maximumElements) {
  49     ImmutableList.Builder<Entity> builder = ImmutableList.<Entity>builder();
  50     for (int i = 0; i < maximumElements; i++) {
  51       if (!hasNext()) {
  52         break;
  53       }
  54       builder.add(datastore.getOriginalNamespaceEntity(next()));
  55     }
  56     return builder.build();
  57   }
  58
  59   @Override
  60   public List<Index> getIndexList() {
  61     return iterator.getIndexList();
  62   }
  63
  64   @Override
  65   public Cursor getCursor() {
  66     return iterator.getCursor();
  67   }
  68
  69   @Override
  70   public void remove() {
  71     iterator.remove();
  72   }
  73 }