Question

我需要大脑！：P

我有一个IDAO接口＆lt; T，K＆gt;，T是实体类，K是主键类。

我开发了一个具体类GenericDAO＆lt; T，K＆gt;，提供CRUD操作和Criteria Queries自动提取（我创建了一个方面@Joinfetch，我在权利关系上使用）。如果你想要我可以显示代码，但它不是主题:)。

这里生产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DAO的另一个实现（例如复杂的提取）。这些实现也通过IDAO外观公开它们的方法。我希望那些DAO的注入方式与GenericDAO相同。

以下是我想要的功能：

我需要注入IDAO的实现＆lt;人，长＆gt;某处。如果存在，则类实现IDAO＆lt;人，长＆gt;那么我希望CDI选择这个实现。否则，如果IDAO没有实现，则＆lt;人，长＆gt;我希望CDI选择GenericDAO＆lt;人，长＆gt;由工厂生产。

我很难用英语解释。我希望你能理解我的问题。

你有最好的做法吗？

谢谢！

Answer 1

我需要两个@Qualifier

@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);
}

IDefaultDAO

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

摘要DAO

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;
}
}

特定的DAO

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

DAO制片人

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;
    }
  }
}

CDI GenericDAO和自定义实现

1 个答案: