Core concepts
The central interface in the Spring Data repository abstraction is Repository
.
It takes the domain class to manage as well as the identifier type of the domain class as type arguments.
This interface acts primarily as a marker interface to capture the types to work with and to help you to discover interfaces that extend this one.
The CrudRepository
and ListCrudRepository
interfaces provide sophisticated CRUD functionality for the entity class that is being managed.
CrudRepository
Interfacepublic interface CrudRepository<T, ID> extends Repository<T, ID> {
<S extends T> S save(S entity); (1)
Optional<T> findById(ID primaryKey); (2)
Iterable<T> findAll(); (3)
long count(); (4)
void delete(T entity); (5)
boolean existsById(ID primaryKey); (6)
// … more functionality omitted.
}
1 | Saves the given entity. |
2 | Returns the entity identified by the given ID. |
3 | Returns all entities. |
4 | Returns the number of entities. |
5 | Deletes the given entity. |
6 | Indicates whether an entity with the given ID exists. |
The methods declared in this interface are commonly referred to as CRUD methods.
ListCrudRepository
offers equivalent methods, but they return List
where the CrudRepository
methods return an Iterable
.
We also provide persistence technology-specific abstractions, such as JpaRepository or MongoRepository .
Those interfaces extend CrudRepository and expose the capabilities of the underlying persistence technology in addition to the rather generic persistence technology-agnostic interfaces such as CrudRepository .
|
Additional to the CrudRepository
, there are PagingAndSortingRepository
and ListPagingAndSortingRepository
which add additional methods to ease paginated access to entities:
PagingAndSortingRepository
interfacepublic interface PagingAndSortingRepository<T, ID> {
Iterable<T> findAll(Sort sort);
Page<T> findAll(Pageable pageable);
}
Extension interfaces are subject to be supported by the actual store module. While this documentation explains the general scheme, make sure that your store module supports the interfaces that you want to use. |
To access the second page of User
by a page size of 20, you could do something like the following:
PagingAndSortingRepository<User, Long> repository = // … get access to a bean
Page<User> users = repository.findAll(PageRequest.of(1, 20));
ListPagingAndSortingRepository
offers equivalent methods, but returns a List
where the PagingAndSortingRepository
methods return an Iterable
.
In addition to query methods, query derivation for both count and delete queries is available. The following list shows the interface definition for a derived count query:
interface UserRepository extends CrudRepository<User, Long> {
long countByLastname(String lastname);
}
The following listing shows the interface definition for a derived delete query:
interface UserRepository extends CrudRepository<User, Long> {
long deleteByLastname(String lastname);
List<User> removeByLastname(String lastname);
}
Entity State Detection Strategies
The following table describes the strategies that Spring Data offers for detecting whether an entity is new:
|
By default, Spring Data inspects the identifier property of the given entity.
If the identifier property is |
|
If a property annotated with |
Implementing |
If an entity implements Note: Properties of |
Providing a custom |
You can customize the |
Cassandra provides no means to generate identifiers upon inserting data.
As consequence, entities must be associated with identifier values.
Spring Data defaults to identifier inspection to determine whether an entity is new.
If you want to use auditing make sure to either use Optimistic Locking or implement |