JPA with Spring Boot

#spring #jpa #java

To use JPA with Spring we need to implement 4 steps:

Define mapping metadata in entities
Define an EntityManagerFactory bean
Define Transaction Manager and DataSource beans
Define Repository/DAO

With Spring Boot, it automatically creates a DataSource, an EntityManagerFactoryBean, and sets up a JpaTransactionManager. So, to use JPA with Spring Boot we just need to implement 2 steps:

Annotate domain classes

@Entity
@Table(name="T_ACCOUNT")
public class Account {

    @Id
    @Column(name="ID")
    private Long entityId;

    @Column(name="CREDIT_CARD")
    private String creditCardNumber;
    ...
}

Define repositories as interfaces

public interface AccountRepository extends Repository<Account,Long> {

    public Account findByCreditCardNumber(String creditCardNumber);
}

Spring Data will implement at run-time scans for interfaces extending Repository. Besides, it will implement CRUD methods (extending CrudRepository), paging and sorting (extending PagingAndSortingRepository), among other subinterfaces. See Repository documentation

Using CrudRepository and custom query (JPQL)

public interface AccountRepository extends CrudRepository<Account,Long> {

    public Account findByCreditCardNumber(String creditCardNumber);

    @Query("SELECT a FROM Account WHERE a.email NOT LIKE '%@%'")
    public List<Account> findInvalidEmails();

}

Using the repository

public class AccountServiceImpl implements AccountService {

    private AccountRepository accountRepository;

    public AccountServiceImpl(AccountRepository accountRepository) {
        this.accountRepository = accountRepository;
    }

    @Transactional
    public Account getAccount(String creditCardNumber) {
        return accountRepository.findByCreditCardNumber(creditCardNumber);
    }

    @Transactional
    public void saveAccount(Account account) {
        accountRepository.save(account);
    }
}