14.3Annotations used for configuring DAO or Repository classes

The best way to guarantee that your Data Access Objects (DAOs) or repositories provide exception translation is to use the@Repositoryannotation. This annotation also allows the component scanning support to find and configure your DAOs and repositories without having to provide XML configuration entries for them.

@Repository
public class SomeMovieFinder implements MovieFinder {
    // ...
}

Any DAO or repository implementation will need to access to a persistence resource, depending on the persistence technology used; for example, a JDBC-based repository will need access to a JDBCDataSource; a JPA-based repository will need access to anEntityManager. The easiest way to accomplish this is to have this resource dependency injected using one of the@Autowired,,@Inject,@Resourceor@PersistenceContextannotations. Here is an example for a JPA repository:

@Repository
public class JpaMovieFinder implements MovieFinder {

    @PersistenceContext
    private EntityManager entityManager;

    // ...

}

If you are using the classic Hibernate APIs than you can inject the SessionFactory:

@Repository
public class HibernateMovieFinder implements MovieFinder {

    private SessionFactory sessionFactory;

    @Autowired
    public void setSessionFactory(SessionFactory sessionFactory) {
        this.sessionFactory = sessionFactory;
    }

    // ...

}

Last example we will show here is for typical JDBC support. You would have theDataSourceinjected into an initialization method where you would create aJdbcTemplateand other data access support classes likeSimpleJdbcCalletc using thisDataSource.

@Repository
public class JdbcMovieFinder implements MovieFinder {

    private JdbcTemplate jdbcTemplate;

    @Autowired
    public void init(DataSource dataSource) {
        this.jdbcTemplate = new JdbcTemplate(dataSource);
    }

    // ...

}

Please see the specific coverage of each persistence technology for details on how to configure the application context to take advantage of these annotations.