
mybatis查询数据库返回数据全为null
springboot框架加mybatis的整合在查询数据时返回数据正确条数但内容全为null。
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异常过程
springboot框架加mybatis的整合在查询数据时返回数据正确条数但内容全为null
mapper.xml
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.ly.mybatis.mapper.EmpMapper">
<!-- List<Emp> getAllEmp();-->
<select id="getAllEmp" resultType="emp">
select * from emp
</select>
</mapper>
Emp.java
private Integer eId;
private String eName;
private Integer eAge;
private String eSex;
private String eEmail;
数据库字段名
test.java
@Test
public void testGetAllEmp(){
SqlSession sqlSession = SqlSessionUtils.getSqlSession();
EmpMapper empMapper = sqlSession.getMapper(EmpMapper.class);
List<Emp> emps = empMapper.getAllEmp();
emps.forEach(emp-> System.out.println(emp));
}
异常结果截图
修改途径
1.在写查询语句时为字段名取别名且别名与属性名相同
mapper.xml
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.ly.mybatis.mapper.EmpMapper">
<!-- List<Emp> getAllEmp();-->
<select id="getAllEmp" resultType="emp">
select e_id eId,e_name eName,e_age eAge,e_sex eSex,e_email eEmail from emp
</select>
</mapper>
结果截图
2.设置mybatis的全局配置
配置文件
mapper.xml
<select id="getAllEmp" resultType="emp">
<!-- select e_id eId,e_name eName,e_age eAge,e_sex eSex,e_email eEmail from emp-->
select * from emp
</select>
结果截图
3.使用resultMap自定义映射关系
mapper.xml
<resultMap id="empResultMap" type="Emp">
<id property="eId" column="e_id"></id>
<result property="eName" column="e_name"></result>
<result property="eAge" column="e_age"></result>
<result property="eSex" column="e_sex"></result>
<result property="eEmail" column="e_email"></result>
</resultMap>
<!-- List<Emp> getAllEmp();-->
<select id="getAllEmp" resultMap="empResultMap">
select * from emp
</select>
结果截图
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