About this section

This exercise section is about how to work with Spring Data JPA.

Below is a table with

• a topic to work on and
• a git branch with a particular exercise to checkout

The topics are in the suggested order for the exercises:

Topic	Git branch	Link to an article/Javadoc
Create some @Query Methods	data_query-methods-ex	spring.io
Create some Derived Query Methods	data_derived-query-methods-ex	spring.io

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Additional resources

Spring data

Spring Data is a module of the Spring Framework that provides a set of tools and abstractions for working with data in a database.

Spring Data makes it easier to work with databases by providing a common interface for working with different data stores, including relational databases, NoSQL databases, and others.

One of the key components of Spring Data is the Repository interface. A Repository provides a high-level abstraction for working with data in a database. It defines a set of methods for creating, reading, updating, and deleting data, and also provides support for querying the data store.

Here's an example of how to define a Repository interface for working with a User entity in a relational database using Spring Data JPA:

public interface UserRepository extends JpaRepository<User, Long> {
    List<User> findByLastName(String lastName);
}

In this example, the UserRepository interface extends the JpaRepository interface, which is a subinterface of Spring Data's Repository interface. The User class represents a database entity, and Long is the type of the entity's primary key.

The findByLastName method is a custom query method that uses Spring Data's method naming convention to generate a query that returns all User entities with the specified last name. This method provides a convenient way to retrieve data from the database without having to write custom SQL queries.

To use the UserRepository in a Spring application, you can inject it into a service or controller using Spring's @Autowired annotation:

@Service
public class UserService {
    @Autowired
    private UserRepository userRepository;
    
    public List<User> getUsersByLastName(String lastName) {
        return userRepository.findByLastName(lastName);
    }
}

In the above example, the UserService class uses the UserRepository to retrieve a list of users by their last name. This service can then be used by a controller to handle requests from a client.