学习笔记——Mybatis映射文件根标签与子标签
2023-01-09一、Mybatis映射文件
1、映射文件根标签
mapping标签：
该标签中的namespace要求与接口的全类名一致
2、映射文件子标签
（1）cache（该命名空间的缓冲配置）
（2）cache-ref（引用其他命名空间的缓存配置）
（3）resultMap（描述如何从数据库结果集中加载对象，是最复杂也是最强大的元素）
注意：resultType解决不了的问题，交给resultMap（一般是多表查询）。
（4）sql（可被其他语句引用的可重用语句块）
（5）insert（映射插入语句）
（6）update（映射更新语句）
（7）delete（映射删除语句）
（8）select（映射查询语句）
3、示例代码
（1）“day02_mybatis.src.main.java.com.hh.mybatis.mapper.EmployeeMapper”中的代码
package com.hh.mybatis.mapper;
import com.hh.mybatis.pojo.Employee;
import java.util.List;
public interface EmployeeMapper {
/**
* 通过id获取员工信息
* @param empId
* @return
*/
public Employee selectEmployee(int empId);
/**
* 添加员工信息
* @param employee
*/
public void insertEmployee(Employee employee);
/**
* 删除员工信息
* @param empId
*/
public void deleteEmployeeById(int empId);
/**
* 修改员工信息
* @param employee
*/
public void updateEmployee(Employee employee);
/**
* 查询所有员工信息
* @return
*/
public List<Employee> selectAllEmps();
}（2）映射文件中的代码（day02_mybatis.src.main.resources.mapper下的EmployeeMapper.xml）
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.hh.mybatis.mapper.EmployeeMapper">
<select id="selectEmployee" resultType="employee">
SELECT
id,
last_name,
email,
salary
FROM
tbl_employee
WHERE
id=#{empId}
</select>
<insert id="insertEmployee">
INSERT INTO
tbl_employee(last_name,email,salary)
VALUES
(#{lastName},#{email},#{salary})
</insert>
<delete id="deleteEmployeeById">
delete from
tbl_employee
where
id=#{empId}
</delete>
<update id="updateEmployee">
update
tbl_employee
set
last_name = #{lastName},
email = #{email},
salary = #{salary}
where
id = #{id}
</update>
<select id="selectAllEmps" resultType="employee">
SELECT
id,
last_name,
email,
salary
FROM
tbl_employee
</select>
</mapper>（3）测试类代码（day02_mybatis.src.test.java.TestMybatis）
import com.hh.mybatis.mapper.EmployeeMapper;
import com.hh.mybatis.pojo.Employee;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Test;
import java.io.IOException;
import java.io.InputStream;
import java.util.List;
public class TestMybatis {
@Test
public void TestMybatis(){
try {
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
//通过sqlSessionFactory获取sqlSession对象
SqlSession sqlSession = sqlSessionFactory.openSession();
//获取EmployeeMapper的代理对象
EmployeeMapper employeeMapper = sqlSession.getMapper(EmployeeMapper.class);
System.out.println("employeeMapper.getClass().getName() = " + employeeMapper.getClass().getName());
Employee employee = employeeMapper.selectEmployee(1);
System.out.println("employee = " + employee);
} catch (IOException e) {
e.printStackTrace();
}
}
/**
* 测试添加员工
*/
@Test
public void TestMybatisInsert(){
try {
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
//通过sqlSessionFactory获取sqlSession对象
SqlSession sqlSession = sqlSessionFactory.openSession();
//获取EmployeeMapper的代理对象
EmployeeMapper employeeMapper = sqlSession.getMapper(EmployeeMapper.class);
// Employee wangwu = new Employee(null,"wangwu","zs@163.com",50.0);
//测试添加员工信息
// employeeMapper.insertEmployee(wangwu);
//测试删除员工信息
// employeeMapper.deleteEmployeeById(2);
// Employee wangwu = new Employee(1,"zhangsan1","zs1@163.com",102.0);
//
// employeeMapper.updateEmployee(wangwu);
//查询所有员工信息
List<Employee> employees = employeeMapper.selectAllEmps();
for (Employee employee : employees) {
System.out.println("employee = " + employee);
}
//提交事务
sqlSession.commit();
} catch (IOException e) {
e.printStackTrace();
}
}
}
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