从 table 检索地图<String,<T>>

Question

我读了一些像this and this这样的信息性帖子，但我仍然很困惑。

Hibernate 版本是 4.3.11 MySQL 帐户 table 是：

Field           Type            Null    Key
Id              int(11)         NO      PRI
Reference       varchar(20)     NO      UNI     
Balance         decimal(10,5)   NO          
Currency        varchar(3)      NO          
Valid           tinyint(1)      NO          
Type            varchar(20)     YES

AccountDaoImpl 方法：

@Override

接受一组有效的帐户参考 @param accountReferences @return A java.util.Map 以账户引用为键，账户实体为值 @throws DaoException

public Map<String, Account> getAccountsByReferences(Collection<String> accountReferences) throws DaoException {
        // TODO Auto-generated method stub

        if (accountReferences == null || accountReferences.isEmpty()) {
            return null;
        }

        if (accountReferences.size() > Constants.MAX_ACCOUNTS_SIMULT) {
            throw new DaoException("Please query " + Constants.MAX_ACCOUNTS_SIMULT + " at a time");
        }

        String accountByRefSQL = "SELECT new map(acc.reference,acc ) FROM Account acc WHERE acc.reference IN (:accountReferences)";

        Session session = null;
        try {
            session = HibernateUtil.getSessionFactory().openSession();

            Query query = session.createQuery(accountByRefSQL).setParameterList("accountReferences", accountReferences);

            return findMany(query);

        } catch (DaoException daoException) {
            log.error("DaoException in AccountDaoImpl.findAccountByReference(...)", daoException);
            throw daoException;
        } catch (HibernateException e) {
            log.error("HibernateException in AccountDaoImpl.findAccountByReference(...)", e);
            throw new DaoException(e.getMessage());
        } finally {
            session.close();
        }
    }

findMany() 方法在父类 GenericDao 中：

public List<T> findMany(Query query) throws DaoException {
        try {
            List<T> t;
            t = (List<T>) query.list();
            return t;
        } catch (HibernateException hibernateExecption) {
            log.error("Hibernate Exception in GenericHibernateDaoImpl.findMany(...)", hibernateExecption);
            throw new DaoException(hibernateExecption.getMessage());
        } catch (RuntimeException runtimeException) {
            log.error("RuntimeException in GenericHibernateDaoImpl.findMany(...)", runtimeException);
            throw new DaoException(runtimeException.getMessage());
        }

    }

有两个问题:

根据我提到的线程，调用是正确的（我不知道如何！）
线程声明 查询将 return 将 return 地图列表 - 我不明白这个

Answer 1

我收到了 this forum thread 的回复。

You are trying to cast a List into a Map. Check out the map() select syntax. The Map is supposed to wrap the ResultSet, but the query returns a List.

I suggest you return a List and then build the Map using a simple iteration.

从 table 检索地图<String,<T>>

Retrieve a Map<String,<T>> from a table

hibernate

hql

hibernate-mapping

hibernate-4.x