[JAVA] [How to install Spring Data Jpa]

① Add a tag to pom.xml.

<!-Settings to enable DataJpa in Spring Boot-> org.springframework.boot spring-boot-starter-data-jpa

② Create an Entity class.

Add [must] @Entity. This indicates that it is an Entity class. Add [must] @Table.name is the name of the DB table. If omitted, it will be mapped to a table with a capitalized class name. [must] Add @Id to the column with PRIMARY KEY. It will not work without @Id. If not, add PRIMARY KEY to DB or Add @GeneratedValue (strategy = GenerationType.IDENTITY). With this, you can generate a PRIMARY KEY. If DB is a composite key, use @ javax.persistence.EmbeddedId

Add [must] @Column and specify the column name to be mapped. If omitted, the property name will be mapped to the column with the capitalized name.

import javax.persistence.Column; import javax.persistence.Entity; import javax.persistence.Id; import javax.persistence.Table;

// Entity class = DB table @Entity @Table(name = "player") public class Player {

@Id
@Column(name = "id")
private Integer id;
@Column(name = "name")
private String name;
@Column(name = "nationality")
private String nationality;

// Getter Setter below

③ Create a repository. Make it with an interface instead of the usual class.

[must] Add the following after the class name.

				⬇		︎
	extends JpaRepository<Player, Integer>

import org.springframework.data.jpa.repository.JpaRepository; import jp.co.rakus.football.entity.Player;

//JpaRepositoryを継承する事で、fineOne、findAll、save、deleteの4メソッドが使用 // Generics specifies the entity's class name and primary key type. public interface PlayerRepository_DataJpa extends JpaRepository<Player, Integer> {

}

④ Now that it is ready, use it in services and controllers.

@Service @EnableTransactionManagement public class PlayerService {

@Autowired
PlayerRepository_DataJpa playerRepository_DataJpa;
	
public List<Player> findAll() {
	return playerRepository_DataJpa.findAll();
}

public void saveUserInfo(User user) {
	userRepositoryDataJpa.save(user);
}

}