Question

我有List propertyIds。我想通过Collections获得propertyIds。这是我的代码：

Collection<Long> propertyIds = externalTaxManager.getPropertyIdsByTaxId(id);  //Return type must be Collection<Long>

这是我的DAOImpl，

public Collection<Long> getPropertyIdsByTaxId(Long externalTaxId) {
    SQLQuery query = currentSession().createSQLQuery("select b.OMH_PROPERTY_ID from OMH_EXTERNAL_TAX a , " +
                "OMH_EXTERNAL_TAX_PROP_XREF b\n" +
                "where a.OMH_EXTERNAL_TAX_ID=b.OMH_EXTERNAL_TAX_ID and a.OMH_EXTERNAL_TAX_ID = :externalTaxId ")
                .addScalar("OMH_PROPERTY_ID" , LongType.INSTANCE);
        query.setParameter("externalTaxId", externalTaxId);
        Collection<BigDecimal> propertyIdsList = (Collection<BigDecimal>) query.list();
    Long val = null;
    Collection<Long> expRes = new HashSet<Long>();
    for(BigDecimal values : propertyIdsList){
       val = values.longValue();
       expRes.add(val);
    }
    return expRes;
}

以上查询在与externalTaxId关联时返回500+个值。

抛出的异常是：

java.lang.ClassCastException: java.math.BigDecimal cannot be cast to java.lang.Long.

怎么了？

Answer 1

查看您的预期回报类型：

Collection<Long>

但是DB返回：

Collection<BigDecimal>

所以，您应该将代码更改为：

Collection<BigDecimal> propertyIdsList =  query.list();

然后尝试以其他方式将BigDecimal强制转换为Long;

^ _ ^原谅我可怜的英语..

Answer 2

以下片段按预期为我工作。

   public Collection<Long> getPropertyIdsByTaxId(Long externalTaxId) {
        SQLQuery query = currentSession().createSQLQuery("select b.OMH_PROPERTY_ID from OMH_EXTERNAL_TAX a , " +
                "OMH_EXTERNAL_TAX_PROP_XREF b\n" +
                "where a.OMH_EXTERNAL_TAX_ID=b.OMH_EXTERNAL_TAX_ID and a.OMH_EXTERNAL_TAX_ID = :externalTaxId ")
                .addScalar("OMH_PROPERTY_ID", LongType.INSTANCE);
        query.setParameter("externalTaxId", externalTaxId);
        Collection<BigDecimal> propertyIdsList = (Collection<BigDecimal>) query.list();
        Long propertyIdsListValue = null;
        Collection<Long> propertyIds = new HashSet<Long>();
        for (BigDecimal propertyId : propertyIdsList) {
            propertyIdsListValue = propertyId.longValue();
            propertyIds.add(propertyIdsListValue);
        }
        return propertyIds;
    }

使用Hibernate获取Collection <long>值时出现异常 - ClassCastException：java.math.BigDecimal无法强制转换为java.lang.Long

2 个答案: