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

   1 package com.google.appengine.api.datastore;
   2
   3 import static com.google.appengine.api.datastore.DataTypeTranslator.getComparablePropertyValue;
   4
   5 import com.google.appengine.api.datastore.Query.SortPredicate;
   6 import com.google.apphosting.datastore.DatastoreV3Pb;
   7 import com.google.apphosting.datastore.DatastoreV3Pb.Query.Filter;
   8 import com.google.apphosting.datastore.DatastoreV3Pb.Query.Order;
   9
  10 import java.util.ArrayList;
  11 import java.util.Collection;
  12 import java.util.Collections;
  13 import java.util.List;
  14
  15 /**
  16  * A comparator with the same ordering as {@link EntityProtoComparators} which uses
  17  * Entity objects rather than protos.
  18  */
  19 class EntityComparator extends BaseEntityComparator<Entity> {
  20
  21   EntityComparator(List<Order> orders) {
  22     super(orders, Collections.<Filter>emptyList());
  23   }
  24
  25   @Override
  26   List<Comparable<Object>> getComparablePropertyValues(Entity entity, String propertyName) {
  27     Object prop;
  28     if (propertyName.equals(Entity.KEY_RESERVED_PROPERTY)) {
  29       prop = entity.getKey();
  30     } else if (!entity.hasProperty(propertyName)) {
  31       return null;
  32     } else {
  33       prop = entity.getProperty(propertyName);
  34     }
  35     if (prop instanceof Collection<?>) {
  36       Collection<?> props = (Collection<?>) prop;
  37       if (props.isEmpty()) {
  38         return Collections.singletonList(null);
  39       }
  40       List<Comparable<Object>> comparableProps = new ArrayList<>(props.size());
  41       for (Object curProp : props) {
  42         comparableProps.add(getComparablePropertyValue(curProp));
  43       }
  44       return comparableProps;
  45     } else {
  46       return Collections.singletonList(getComparablePropertyValue(prop));
  47     }
  48   }
  49
  50   static EntityComparator fromSortPredicates(List<SortPredicate> sortPredicates) {
  51     List<DatastoreV3Pb.Query.Order> orders = new ArrayList<>(sortPredicates.size());
  52     for (SortPredicate predicate : sortPredicates) {
  53       orders.add(QueryTranslator.convertSortPredicateToPb(predicate));
  54     }
  55     return new EntityComparator(orders);
  56   }
  57 }