hibernate - 从表中全选 hibernate

Question

所以我有以下代码:

Query query = session.createQuery("from Weather");
        List<WeatherModel> list = query.list();
        WeatherModel w = (WeatherModel) list.get(0);

我不会从Weather表中获取所有项目，但会不断出现以下错误:(第23行是我创建查询的地方)

java.lang.NullPointerException
    at action.WeatherAction.validate(WeatherAction.java:23)
    at com.opensymphony.xwork2.validator.ValidationInterceptor.doBeforeInvocation(ValidationInterceptor.java:251)
    at com.opensymphony.xwork2.validator.ValidationInterceptor.doIntercept(ValidationInterceptor.java:263)............

有什么问题？

Answer 1

Query query = session.createQuery("from Weather"); //You will get Weayher object
List<WeatherModel> list = query.list(); //You are accessing  as list<WeatherModel>

他们都是不同的实体

Query query = session.createQuery("from Weather"); 

 List<Weather> list = query.list(); 

Weather w = (Weather) list.get(0);