Planned lessonJNR-029-L01

Repository interfaces

On This Lesson 4 topics

This lesson is planned. The outline below lists the topics it will cover. The full lesson has not been published yet.

In this lesson

get a working repository by declaring an interface.

Extend JpaRepository<Entity, IdType>; Spring generates the implementation at startup.
You get findById, findAll, save, deleteById, count, and paging for free.
save inserts a new entity or merges an existing one; for managed entities it is not needed for updates.
findById returns an Optional.
Repositories belong to the persistence layer; services use them, controllers do not.

Draft outline details

java

public interface ProductRepository extends JpaRepository<Product, Long> {
}

Who writes the implementation class?

Show answer

Spring Data, generated at runtime.

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