Mybatis报错——java.util.HashMap cannot be cast to com.bean.Employee
2017-12-24 11:45
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Mybatis报错——java.lang.ClassCastException: java.util.HashMap cannot be cast to com.bean.Employee
报错如下:java.lang.ClassCastException: java.util.HashMap cannot be cast to com.bean.Employee
at com.test.Test_crud.test4(Test_crud.java:129)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606) at
org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
………………….
………………….
错误代码:
Mapper接口中的代码:
//模糊查询返回map集合 public Map<String,Employee> getEmpsByLastNameLike(String lastname);
映射文件中的代码:
<select id="getEmpsByLastNameLike" resultType="map"> select * from tbl_employee where last_name like #{lastname} </select>
错误原因:在mybatis中如果返回的是一个集合,要写集合中的元素类型 ,而不是集合的类型。即resultType=”“的值是集合中元素类型。而代码中写成了集合的类型,所以报错——HashMap不能被转换为 com.bean.Employee。
问题解决:
将resultType=”map”修改为resultType=”com.bean.Employee”:
<select id="getEmpsByLastNameLike" resultType="com.bean.Employee"> select * from tbl_employee where last_name like #{lastname} </select>
注意:
1.resultType=”“指的是每一条记录要被封装成什么类型,
2.Mapper接口定义的返回值(
Map<String,Employee>)
Map指定了结果集的类型,Employee指定了结果集中每一条记录将会封装成什么类型。
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