Connecting to a Real Database, thesarfo

Connecting to a real database in Spring Boot isn’t much config — just add the connection details to application.properties:

spring.datasource.name=
spring.datasource.url=
spring.datasource.username=
spring.datasource.password=

For Postgres, install it locally and create a DB for the project (or use Docker instead).

The schema.sql file is picked up automatically by embedded databases (H2) — for a real database you have to opt in explicitly:

spring.sql.init.mode=always

There are several ways to connect to a real DB — locally installed, Docker, Docker Compose. Using the Docker approach: on start.spring.io, add the Postgres driver dependency and the Docker Compose dependency. The latter looks at your other selected dependencies (Postgres) and generates a compose.yaml for you.

JDBC vs. Spring Data JPA

With JDBC you write your own SQL queries. With JPA, Hibernate handles that as an ORM. To use Spring Data JPA, add the dependency, then make your repository extend ListCrudRepository (returns a List) or CrudRepository (returns an Iterable) — both provide standard CRUD out of the box. Both take two type parameters: the entity type, and its id type.

public interface RunRepository extends ListCrudRepository<Run, Integer> {
}

That’s it for basic CRUD. For something custom — say, finding runs by location — add a method to the same repository:

// RunRepository
public interface RunRepository extends ListCrudRepository<Run, Integer> {
    List<Run> findAllByLocation(String location);
}

And expose it from the controller:

// RunController — location as a path variable here, though it could be a query param too
@GetMapping("/location/{location}")
List<Run> findByLocation(@PathVariable String location) {
    return runRepository.findAllByLocation(location);
}