问使用@Transactional(readOnly = true)有哪些优点？

EN

/**
 * Repository class for <code>Pet</code> domain objects All method names are compliant with Spring Data naming
 * conventions so this interface can easily be extended for Spring Data See here: http://static.springsource.org/spring-data/jpa/docs/current/reference/html/jpa.repositories.html#jpa.query-methods.query-creation
 *
 * @author Ken Krebs
 * @author Juergen Hoeller
 * @author Sam Brannen
 * @author Michael Isvy
 */
public interface PetRepository extends Repository<Pet, Integer> {

    /**
     * Retrieve all {@link PetType}s from the data store.
     * @return a Collection of {@link PetType}s.
     */
    @Query("SELECT ptype FROM PetType ptype ORDER BY ptype.name")
    @Transactional(readOnly = true)
    List<PetType> findPetTypes();

    /**
     * Retrieve a {@link Pet} from the data store by id.
     * @param id the id to search for
     * @return the {@link Pet} if found
     */
    @Transactional(readOnly = true)
    Pet findById(Integer id);

    /**
     * Save a {@link Pet} to the data store, either inserting or updating it.
     * @param pet the {@link Pet} to save
     */
    void save(Pet pet);

}