[英]HQL - difference between two same queries
Why does this query work normal:为什么这个查询工作正常:
Query query = session.createQuery("from Table tab");
And this query:这个查询:
Query query = session
.createQuery("select tab.col1, tab.col2, tab.col3 from Table tab");
And that's what I'm doing with both queries:这就是我对这两个查询所做的:
dataList = query.list();
for (Table item : dataList)
{
System.out.println(item.getCol1();
}
reports:报告:
java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to table.Table
at test.TestCriteria.main(TestCriteria.java:35)
Could you help?你能帮忙吗?
Table is normally mapped in entity bean and all the columns are correct.表通常映射到实体 bean 中,所有列都是正确的。
I believe in the second query
, the result is a List<Object[]>
:我相信第二个
query
,结果是一个List<Object[]>
:
Object[] row = (Object[]) dataList.get(i);
Object col1Value = row[0];
Object col2Value = row[1];
Object col3Value = row[2];
I have this guess observing Ljava.lang.Object;
我有这个猜测观察
Ljava.lang.Object;
in the exception trace.在异常跟踪中。
The result of query select tab.col1, tab.col2, tab.col3
returns list of object array which contains the selected fields ie col1, col2 & col3.查询
select tab.col1, tab.col2, tab.col3
的结果返回 object 数组的列表,其中包含所选字段,即 col1、col2 和 col3。
Then from the object array, you can extract fields by their index.然后从 object 数组中,您可以按索引提取字段。
for(Object[] field : dataList){
col1 = field[0]; //-- Casting accordingly
col2 = field[1];
col3 = field[2];
}
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