Issue
in Spring Boot and JPA there is the interface JpaRepository, which already provides the most important methods like findAll, saveAll. Is there also such an interface for the associated RestService?
If not, how could one proceed to define such an interface. I have looked into JpaRepository once, there the methods are not coded out. But also only with List<T> findAll(); specified, where is the actual code?
Thanks a lot
Solution
the methods are not coded out. But also only with List findAll(); specified, where is the actual code?
JpaRepository is just an interface meaning it provides just the declarations and signatures of what should be available from that interface.
JpaRepository is a way from spring to take advantage of JPA layer and provide some additional commonly used functionalities very useful to the programmer.
Having said that it is important to understand that JPA layer follows JPA specification, and is just that, a specification not an implementation. Multiple providers come and provide their implementation as far as they comply with this specification. Those providers (ex hibernate, eclipseLink, DataNucleus) provide the functionality of JPA layer. Those providers, provide the code to communicate with database and do the actual work of jpa layer.
What JpaRepository does, is that it takes advantage of this JPA layer and provides some extra functionality by invoking what is necessary on the jpa layer and expose some common functionalities. So JpaRepository will not communicate directly with database using native queries but instead use the jpa layer offered from example from hibernte and provide some jpa query to hibernate to retrieve what it wants.
Inside Spring you can find some implementation classes of JpaRepository like SimpleJpaRepository.class but again they don't provide end to end functionality but instead just communicate through jpa layer indirectly with a provider like hibernate to provide some commonly used functionality to the programmer.
Answered By - Panagiotis Bougioukos
Answer Checked By - Marie Seifert (JavaFixing Admin)
