问题描述

Cannot cast from List<Object> to List<Professor>

一个简单的Spring mvc mybatis框架的CRUD实例。但是下面DAOIMPL里面代码报错，改不了首先interface IProfessorDao写了
public List findAll();

然后IProfessorDaoImpl里面下面方法报错

public List findAll()

{

// TODO Auto-generated method stub

String sql = this.getStatementId(Professor.class, SELECTALL);

List list = (List)sqlSession.selectList(sql);
return list;

}
其中(List)sqlSession.selectList(sql); 这里提示 Cannot cast from List to List
SQLMAPPER设置也没有问题，代码如下

select * from ALL_EXP_LIST_TBL ;

求助怎么解决

解决方案

可以改成List list = (List)sqlSession.selectList(sql);试试，List是转换不成List的

解决方案二：

• Set & Map?? A?? ?--? object/key exists in set/map???B????--? object/key to be added to set/map?? If and only if???????? (B?==?A || B.equals(A)) &&?B.hashCode == A.hashCode???then??keyAdd will overwr......
  答案就在这里：What's the effect of hashCode() & equals() when adding object to List/Set/Map

解决方案三：

可以改成List《Professor》 list = (List《Professor》)sqlSession.selectList(sql);试试，List《Professor》是转换不成List《Object》的