四、数据库表中的字段名与实体类属性名不相同，可用resultMap解决

四、数据库表中的字段名与实体类属性名不相同，可用resultMap解决

1.准备表和数据

CREATE TABLE teacher(
t_id number(8) PRIMARY KEY,
t_name VARCHAR2(30)
);

INSERT INTO teacher(t_id,t_name) VALUES(10001,'LS1');
INSERT INTO teacher(t_id,t_name) VALUES(10002,'LS2');

2.定义实体类

public class Teacher {

	private int t_id;
	private String tname;
	public Teacher() {
	}
	public Teacher(int t_id, String tname) {
		super();
		this.t_id = t_id;
		this.tname = tname;
	}
	public int getT_id() {
		return t_id;
	}
	public void setT_id(int t_id) {
		this.t_id = t_id;
	}
	public String getTname() {
		return tname;
	}
	public void setTname(String tname) {
		this.tname = tname;
	}
	@Override
	public String toString() {
		return "Teacher [t_id=" + t_id + ", tname=" + tname + "]";
	}
	
}

3.通过resultMap实现对teacher的查询  teacherMapper.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.mybatis.entity.teacherMapper">
	<resultMap type="Teacher" id="TeacherResultMap">
		<id column="t_id" property="t_id"/>
		<result column="t_name" property="tname"/>
	</resultMap>
	<select id="getAllTeacher" resultMap="TeacherResultMap">
		select * from teacher 
	</select>
</mapper>

4.在conf.xml文件中注册classMapper.xml，设置entity的别名

	<typeAliases>
		<typeAlias type="com.mybatis.entity.Teacher" alias="Teacher"/>
	</typeAliases>
	<mappers>
		<mapper resource="com/mybatis/entity/teacherMapper.xml" />
	</mappers>

5.测试

	@Test
	public void selectAll(){
		try {
			String statement = "com.mybatis.entity.teacherMapper.getAllTeacher";
			List<Teacher> teachers = null;
			teachers = session.selectList(statement);
			System.out.println(teachers);
		} catch (Exception e) {
			e.printStackTrace();
		}
	}

resultMap的属性：

id属性resultMap标签的标识。

type属性返回值的全限定类名，或类型别名。

子元素属性：

id元素 ，     用于设置主键字段与领域模型属性的映射关系.

result元素 ，用于设置普通字段与领域模型属性的映射关系

column为数据库表中列名
property为类中属性名 如：Teacher中的tname属性与teacher表中的t_name属性