repository-query-return-types-reference.adoc

Repository query return types

Supported query return types

The following table lists the return types generally supported by Spring Data repositories. However, consult the store-specific documentation for the exact list of supported return types, because some listed here might not be supported in a particular store.

Note	Geospatial types like (GeoResult, GeoResults, GeoPage) are only available for data stores that support geospatial queries.

Table 1. Query return types

Return type	Description
void	Denotes no return value.
Primitives	Java primitives.
Wrapper types	Java wrapper types.
T	An unique entity. Expects the query method to return one result at most. In case no result is found null is returned. More than one result will trigger an IncorrectResultSizeDataAccessException.
Iterator<T>	An Iterator.
Collection<T>	A Collection.
List<T>	A List.
Optional<T>	A Java 8 or Guava Optional. Expects the query method to return one result at most. In case no result is found Optional.empty()/Optional.absent() is returned. More than one result will trigger an IncorrectResultSizeDataAccessException.
Stream<T>	A Java 8 Stream.
Future<T>	A Future. Expects method to be annotated with @Async and requires Spring’s asynchronous method execution capability enabled.
CompletableFuture<T>	A Java 8 CompletableFuture. Expects method to be annotated with @Async and requires Spring’s asynchronous method execution capability enabled.
ListenableFuture	A org.springframework.util.concurrent.ListenableFuture. Expects method to be annotated with @Async and requires Spring’s asynchronous method execution capability enabled.
Slice	A sized chunk of data with information whether there is more data available. Requires a Pageable method parameter.
Page<T>	A Slice with additional information, e.g. the total number of results. Requires a Pageable method parameter.
GeoResult<T>	A result entry with additional information, e.g. distance to a reference location.
GeoResults<T>	A list of GeoResult<T> with additional information, e.g. average distance to a reference location.
GeoPage<T>	A Page with GeoResult<T>, e.g. average distance to a reference location.