[Spring Data JPA] 3-8. Repository query return types

1. Supported Query Return Types

void	no return value
Primitives	Java primitives
Wrapper types	Java wrapper types
T	A unique entity - Expects the query method to return one result at most.  - If no result is found, null is returned.
Iterator<T>	An Iterator
Collection<T>	A Collection
List<T>	A List
Optional<T>	A Java 8 or Guava Optional - Expects return one result at most. (IncorrectResultSizeDataAccessException) - If no result is found, Optional.empty() or Optional.absent() is returned.
Option<T>	Either a Scala or Vavr Option type - Semantically the same behavior as Java 8’s Optional, described earlier.
Stream<T>	A Java 8 Stream
Streamable<T>	A convenience extension of Iterable -  directly exposes methods to stream (map, filter results, concatenate them etc)
Streamable impl constructor (Streamable)	constructor factory method taking a Streamable as argument (….of(…)/….valueOf(…))
Vavr Seq, List, Map, Set	Vavr collection types
Future<T>	A Future - Expects a method to be annotated with @Async - Requires Spring’s asynchronous method execution capability to be enabled
CompletableFuture<T>	A Java 8 CompletableFuture - Expects a method to be annotated with @Async - Requires Spring’s asynchronous method execution capability to be enabled
Slice<T>	A sized chunk of data with an indication of whether there is more data available. - Requires a Pageable method parameter
Page<T>	A Slice with additional information, such as the total number of results. - Requires a Pageable method parameter
Window<T>	A Window of results obtained from a scroll query. - Provides ScrollPosition to issue the next scroll query. - Requires a ScrollPosition method parameter.
GeoResult<T>	A result entry with additional information (distance)
GeoResults<T>	A list of GeoResult<T> with additional information (the average distance)
GeoPage<T>	A Page with GeoResult<T> (the average distance)
Mono<T>	A Project Reactor Mono emitting zero or one element using reactive repositories. - Expects return one result at most. (IncorrectResultSizeDataAccessException) - If no result is found, Mono.empty() is returned.
Flux<T>	A Project Reactor Flux emitting zero, one, or many using reactive repositories. - can emit also an infinite number of elements
Single<T>	A RxJava Single emitting a single element using reactive repositories. - Expects return one result at most. (IncorrectResultSizeDataAccessException) - If no result is found, Mono.empty() is returned.
Maybe<T>	A RxJava Maybe emitting zero or one element using reactive repositories. - Expects return one result at most. (IncorrectResultSizeDataAccessException) - If no result is found, Mono.empty() is returned.
Flowable<T>	A RxJava Flowable emitting zero, one, or many elements using reactive repositories. - can emit also an infinite number of elements.

 

 

IncorrectResultSizeDataAccessException

• More than one result triggers

 

 

출처

• Spring Data JPA document - Repository query return type