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我有两个模型，Purchase和Tag。
购买可以有许多标签（一对多关系）。

退回所有具有一个或多个标签的购买的最佳（有效/清洁/等）方式是什么？（不必返回实际的标签实体）。

我目前正在使用购买表中的一列来确定它是否已被标记但想将其删除（请参阅 PurchaseDAO 以了解它已被使用）

购买控制器：

@RequestMapping(value = "purchases/tagged", method = RequestMethod.GET)
@ResponseBody
public final List<Purchase> getTagged()
{
    return RestPreconditions.checkNotNull(purchaseService.getTagged());
}

@RequestMapping(value = "purchases/pending", method = RequestMethod.GET)
@ResponseBody
public final List<Purchase> getPending()
{
    return RestPreconditions.checkNotNull(purchaseService.getPending());
}


购买服务：

@Service
public class PurchaseService implements IPurchaseService
{
    @Autowired
    private IPurchaseDAO purchaseDAO;

    public PurchaseService()
    {

    }

    @Transactional
    public List<Purchase> getAll()
    {
        return purchaseDAO.findAll();
    }

    @Transactional
    public List<Purchase> getPending()
    {
        return purchaseDAO.getPending();
    }

    @Transactional
    public List<Purchase> getTagged()
    {
        return purchaseDAO.getTagged();
    }
}


购买DAO：

@Repository
public class PurchaseDAO extends AbstractJpaDAO<Purchase> implements IPurchaseDAO {

    @PersistenceContext
    EntityManager entityManager;

    public PurchaseDAO() {
        setClazz(Purchase.class);
    }

    public  List<Purchase> getPending() {
        return entityManager.createQuery("from Purchase where tagged = 0")
                .getResultList();
    }

    public  List<Purchase> getTagged() {
        return entityManager.createQuery("from Purchase where tagged = 1")
                .getResultList();
    }
}


我的 Purchase 和 Tag DAO 都扩展了以下AbstractJpaDAO：

public abstract class AbstractJpaDAO<T extends Serializable> implements
        IAbstractJpaDAO<T> {

    private Class<T> clazz;

    @PersistenceContext
    EntityManager entityManager;

    public void setClazz(final Class<T> clazzToSet) {
        this.clazz = clazzToSet;
    }

    public T findOne(final Long id) {
        return entityManager.find(clazz, id);
    }

    public List<T> findAll() {
        return entityManager.createQuery("from " + clazz.getName())
                .getResultList();
    }

    public void save(final T entity) {
        entityManager.persist(entity);
    }
}

谢谢

JB 建议更新

将 PurchaseDAO getTagged() 更改为：

public  List<Purchase> getTagged() {
        return entityManager.createQuery("SELECT p FROM Puchase p INNER JOIN p.tags")
                .getResultList();
    }

我收到以下错误：

TRACE [http-bio-8080-exec-3] o.s.w.c.s.AnnotationConfigWebApplicationContext [AbstractApplicationContext.java:322] Publishing event in Root WebApplicationContext: ServletRequestHandledEvent: url=[/PurchaseAPIServer/api/purchases/tagged]; client=[192.168.1.17]; method=[GET]; servlet=[PurchaseAPIServer]; session=[null]; user=[null]; time=[411ms]; status=[failed: org.springframework.dao.InvalidDataAccessApiUsageException: org.hibernate.hql.ast.QuerySyntaxException: Puchase is not mapped [SELECT p FROM Puchase p JOIN p.tags tag]; nested exception is java.lang.IllegalArgumentException: org.hibernate.hql.ast.QuerySyntaxException: Puchase is not mapped [SELECT p FROM Puchase p JOIN p.tags tag]]
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1 回答 1

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select p from Purchase p inner join p.tags

内部连接只是使购买至少有一个标签。

于 2012-06-03T15:17:54.003 回答