CDI GenericDAO和自定义实现

Question

我需要大脑！:p

我有一个接口IDAO< T，K >，T是实体类，K是主键类。

我已经开发了一个具体的类Joinfetch，K >，它提供了带有自动抓取的CRUD操作和标准查询(我已经创建了一个方面@ GenericDAO<，我用在实体关系上)。如果您愿意，我可以显示代码，但它不是主题:)。

这里是生成GenericDAO的工厂：

public class GenericDAOProducer {

@PersistenceContext
EntityManager em;

@Produces
@Default
public <T, K> IDAO<T, K> producesGenericDAO(
        final InjectionPoint injectionPoint) {
    final ParameterizedType type = (ParameterizedType) injectionPoint
            .getType();
    // Because of the new, i got to inject the class and the entity manager
    // manualy
    final IDAO<T,K> dao = new GenericDAO<T, K>(this.em,
            (Class) type.getActualTypeArguments()[0]);
    dao.init(); //cool stuff here to prepare some criteria queries
    return dao;
}
}

有时我需要DAOs的另一个实现(例如复杂的抓取)。这些实现也通过IDAO外观公开了它们的方法。我希望这些DAO以与GenericDAO相同的方式注入。

下面是我在示例中想要的特性：

我需要一个注射的实现IDAO<的人，Long>某处。如果存在实现CDI，Long>的类，那么我希望IDAO<选择这个实现。否则，如果IDAO< Person没有实现，我希望Long>选择GenericDAO< Person，Long > produced by the Factory。

这对我来说很难用英语来解释。我希望你能理解我的问题。

你有这样做的最佳实践吗？

谢谢!

Answer 1

我需要两个@限定符

@Qualifier
@Retention(RUNTIME)
@Target({ METHOD, FIELD, PARAMETER, TYPE })
public @interface Generic {}


@Qualifier
@Retention(RUNTIME)
@Target({ METHOD, FIELD, PARAMETER, TYPE })
public @interface Specific {
Class<?> classe();
}

IDAO接口

public interface IDAO<T, PK> extends Serializable {

public abstract T create(T entity) throws DAOException;

public abstract T edit(T entity) throws DAOException;

public abstract void remove(T entity) throws DAOException;

public abstract T find(PK id) throws DAOException;

public abstract T findWithFetch(PK id) throws DAOException;

public abstract List<T> findAll();

public abstract T getRef(PK id);
}

The IDefaultDAO

public interface IDefaultDAO<T, PK> extends IDAO<T, PK> {
public void setEntityClass(final Class<T> entityClass);
}

抽象的道

public abstract class AbstractDAO<T, PK> implements IDAO<T, PK> {

@PersistenceContext
protected EntityManager em;

@Inject
protected transient Logger logger;

protected Class<T> entityClass;

protected final Class<T> getEntityClass() {
    if (this.entityClass == null) {
        this.entityClass = ((Class) ((ParameterizedType) this.getClass()
                .getGenericSuperclass()).getActualTypeArguments()[0]);

    }
    return this.entityClass;
}

//methods implementations
}

默认DAO

@Generic
public class DefaultDAO<T, PK> extends AbstractDAO<T, PK> implements
    IDefaultDAO<T, PK> {

@Override
public void setEntityClass(final Class<T> entityClass) {
    this.entityClass = entityClass;
}
}

一个特定的DAO

@Specific(classe=Delegation.class)
public class DelegationDAO extends AbstractDAO<Delegation, Integer>
implements IDAO<Delegation, Integer> {
// do things differently
}

DAO制作人

public class GenericDAOProducer {

@Inject
private transient Logger logger;

@Produces
public <T, PK> IDAO<T, PK> producesDAO(final InjectionPoint injectionPoint,
        @Generic final IDefaultDAO<T, PK> genericDAO,
        @Any Instance<IDAO<T, PK>> specDAOInstance) {

    // JPA Class (T)
    final ParameterizedType type = (ParameterizedType) injectionPoint
            .getType();
    final Class<T> entityClass = (Class) type.getActualTypeArguments()[0];

    this.logger.info("Search DAO " + entityClass);

    // Search specific DAO

    specDAOInstance = specDAOInstance.select(new SpecificLiteral(
            entityClass));

    if ((specDAOInstance != null) && !specDAOInstance.isAmbiguous()
            && !specDAOInstance.isUnsatisfied()) {
        this.logger.info("Implementation found! ");
        return specDAOInstance.get();
    } else {

        this.logger
                .info("Implementation not found! Return generic DAO."
                        + entityClass);

        genericDAO.setEntityClass(entityClass);
        return genericDAO;
    }
  }
}