Java 使用Hibernate Criteria时，List类型的表达式需要unchecked转换才能符合List<Student>
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The expression of type List needs unchecked conversion to conform to List<Student>, when using Hibernate Criteria
提问by just_a_girl
I have this piece of code that gives the warning mentioned in the title:
我有这段代码给出了标题中提到的警告：
List<Student> studentList = session.createCriteria(Student.class)
.add(Restrictions.eq("indexNumber", indexNum))
.list();
I've read the thread How do I fix "The expression of type List needs unchecked conversion...'?and there's a great solution by @BrunoDeFraine:
我已经阅读了线程如何修复“列表类型的表达式需要未经检查的转换...”？@BrunoDeFraine 提供了一个很好的解决方案：
public static <T> List<T> castList(Class<? extends T> clazz, Collection<?> c) {
List<T> r = new ArrayList<T>(c.size());
for(Object o: c)
r.add(clazz.cast(o));
return r;
}
then I can just do this:
那么我可以这样做：
List<SyndEntry> entries = castList(SyndEntry.class, sf.getEntries());
This works great, but in my case I have Criteria as argument, not class and collection. My question is, can this method be adapted to have criteria as argument, or should I simply use @SuppressWarnings("unchecked")?
这很好用，但在我的情况下，我将 Criteria 作为参数，而不是类和集合。我的问题是，这种方法是否可以适用于将标准作为参数，还是应该简单地使用 @SuppressWarnings("unchecked")？
采纳答案by Taylor
Moved from comment:
You want to cast a Criteria object? That makes no sense. criteria.list()returns a List, so you could just use that.
移自评论：您想投射 Criteria 对象吗？这是没有意义的。criteria.list()返回一个列表，所以你可以使用它。
The castListmethod is odd anyways, you don't gain any compile-time type-safety (it will still only fail at runtime if something is wrong), and it could slow things down, especially if the list is long. I'd just use @SuppressWarnings or live with the warning.
castList无论如何，该方法很奇怪，您不会获得任何编译时类型安全性（如果出现错误，它仍然只会在运行时失败），并且可能会减慢速度，尤其是在列表很长的情况下。我只是使用@SuppressWarnings 或接受警告。
