Question

我有一个通用DAO类看起来像这个:

public class GenericDaoJpa <T extends DomainObject> implements GenericDao<T> {

    private final Class<T> type;

    @PersistenceContext(type=PersistenceContextType.TRANSACTION, unitName="myPersistenceUnit")
    protected EntityManager entityManager;

    public GenericDaoJpa(Class<T> type) {
        super();
        this.type = type;
    }

    public void setEntityManager(EntityManager entityManager) {
        this.entityManager = entityManager;
    }

    public T get(Object id) {
        return (T) entityManager.find(type, id);
    }
}

执行 DAO 类看起来是这样的:

    @Repository("appDao")
    public class ProductDaoJpa extends GenericDaoJpa<Product> implements ProductDao{

    public ProductDaoJpa() {
        super(Product.class);
    }

    public List<Product> getAllProducts() {
        return getAll();
    }   
}

我为不同的数据库配置了另一个名为我的第二支持单位的持久性单位。我想创建一个新的 DAO 类, 它将扩展通用 DaoJpa 类, 但使用不同的持续单位。我如何才能扩展通用 DaoJpa 类, 但对每个 DAO 使用不同的永久单位?

我试图把这个声明移到 DAO 的每类中, 但这导致母类没有编译, 因为它没有提到实体管理者。

@PersistenceContext(type=PersistenceContextType.TRANSACTION, unitName="myPersistenceUnit")
protected EntityManager entityManager;

Answer 1

尝试使用方法注射代替 :

public class GenericDaoJpa <T extends DomainObject> implements GenericDao<T> {

    @PersistenceContext(type=PersistenceContextType.TRANSACTION, unitName="myPersistenceUnit")
    public void setEntityManager(EntityManager entityManager) {
        this.entityManager = entityManager;
    }
}

需要使用不同PU的儿童类别:

@Repository("appDao")
public class ProductDaoJpa extends GenericDaoJpa<Product> implements ProductDao{

    @Override
    @PersistenceContext(type=PersistenceContextType.TRANSACTION, unitName="mySecondPersistenceUnit")
    public void setEntityManager(EntityManager entityManager) {
        this.entityManager = entityManager;
    }
}

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