Using Spring Data JDBC in a Spring Boot app

Question

I'm looking for information about how to configure Spring Data JDBC in a Spring Boot app (a Gradle example would be ideal).

I've read through the docs, and I know that I need to define a Repository implementation for each domain class (or "aggregate" of domain classes), e.g.

interface UserRepository extends CrudRepository<User, Long> {

  // custom query methods
  long countByLastname(String lastname);
}

But it's not entirely clear what dependencies need to be added, how to inject the repository beans into other beans, how to specify to Spring where the repository beans can be found, etc.

I'd particularly like to see how to define a repository that manages more than one table/domain class. For example a repository that manages persistence of an Order and it's collection of OrderItems. The examples in the docs only show how to map a single domain class to a repository.

Answer 1

Since you're using Spring Boot to develop your application, you can leverage the starter Spring modules. In the specific case the dependency would be

implementation 'org.springframework.boot:spring-boot-starter-data-jdbc'

The module version will be picked up automatically if you configured the Gradle Spring plugin

id 'org.springframework.boot' version '2.1.2.RELEASE' // Your version

When you create custom Repository interfaces, you just need to annotate them with the class annotation @Repository. The Spring-autoconfigured scanning mechanism will pick them up automatically (remember to place them in a sub-package, having the @SpringBootApplication annotated class as root).

You can then @Autowire your Repository in a Service, or whatever you want, using hopefully constructor injection.

@Autowired
MyClass(final MyRepository repository) { ... }

Note that if you have a single constructor, you don't need to specify the @Autowired annotation.

Btw, the Data JDBC is a pretty new project. There are limitations, but I suppose you've found them in the Data JDBC documentation.

Answer 2

what dependencies need to be added

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-jdbc</artifactId>
</dependency>

how to inject the repository beans into other beans

In your controller or service or any other bean, you can autowire this repository:-

private final UserRepository userRepository;

@Autowired
public UserController(UserRepository userRepository) {
    this.userRepository = userRepository;
}

how to specify to Spring where the repository beans can be found

Spring Boot will automatically scan the package (and sub-packages) where you have your main class annotated with @SpringBootApplication defined.

Also, annotate your interface with @Repository:-

@Repository
interface UserRepository extends CrudRepository<User, Long> {