4.mybatis属性和表的列名不相同时的处理方法

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/**
* 属性和表的列名不相同时的处理方法
* 1.sql中给列重新命名：
* select tid id, tname name from teacher t where tid=#{id}
* 2.在teacherMapper.xml中使用resultMap标签
* <select id="getTeacher2" parameterType="int" resultMap="getTeacherMap">
*select * from teacher where tid=#{id}
*</select>
*<resultMap type="Teacher" id="getTeacherMap">
*<id property="id" column="tid"/>
*<result property="name" column="tname"/>
*</resultMap>
* @author 魅力_小生
*
*/

mysql表：Teacher[tid, tname], Java 实体类：Teacher[id, name]

建表语句：

create table
CREATE TABLE `teacher` (
`tid` int(11) NOT NULL auto_increment,
`tname` varchar(20) default NULL,
PRIMARY KEY (`tid`)
) 添加2条数据：
1 老师A
2 老师B

Teacher实体类：

public class Teacher {
private int id;
private String name; public Teacher() {
super();
}
public Teacher(int id, String name) {
super();
this.id = id;
this.name = name;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
@Override
public String toString() {
return "Teacher [id=" + id + ", name=" + name + "]";
}}

一、第一种处理方法：sql中给列重新命名

select tid id, tname name from teacher t where tid=#{id}

1.1 写实体类关联的MapperXML：

<mapper namespace="com.mlxs.mybatis.test3.teacherMapper">

<select id="getTeacher" parameterType="int" resultType="Teacher">
select tid id, tname name from teacher t where tid=#{id}
</select>
</mapper>

1.2 写java测试类

/**
* 属性和表的列名不相同时的2种处理方法
* 1.sql中给列重新命名：
* select tid id, tname name from teacher t where tid=#{id}
* @author 魅力_小生
*
*/
@Test
public void getTeacher(){
//创建session，设置事务为true
SqlSession session = MyBatisUtil.getSessionFactory().openSession(true);
String statement = "com.mlxs.mybatis.test3.teacherMapper.getTeacher";
Teacher teacher = session.selectOne(statement, "1");
System.out.println("teacher--->"+teacher);
session.close();
}

1.3 结果

teacher--->Teacher [id=1, name=老师A]

二、第二种处理方法：使用resultMap标签

2.1 写实体类关联的MapperXML：

<mapper namespace="com.mlxs.mybatis.test3.teacherMapper"> 
<select id="getTeacher2" parameterType="int" resultMap="getTeacherMap">
select * from teacher where tid=#{id}
</select>
<resultMap type="Teacher" id="getTeacherMap">
<id property="id" column="tid"/>
<result property="name" column="tname"/>
</resultMap>
</mapper>

2.2 Java测试类

/**
* 属性和表的列名不相同时的2种处理方法
* 2.在teacherMapper.xml中使用resultMap标签
* <select id="getTeacher2" parameterType="int" resultMap="getTeacherMap">
* select * from teacher where tid=#{id}
* </select>
* <resultMap type="Teacher" id="getTeacherMap">
* <id property="id" column="tid"/>
* <result property="name" column="tname"/>
* </resultMap>
* @author 魅力_小生
*
*/
@Test
public void getTeacher2(){
//创建session，设置事务为true
SqlSession session = MyBatisUtil.getSessionFactory().openSession(true);
String statement = "com.mlxs.mybatis.test3.teacherMapper.getTeacher2";
Teacher teacher = session.selectOne(statement, "1");
System.out.println("teacher--->"+teacher);
session.close();
}