學習筆記——Mybatis映射文件根標簽與子標簽

2023-01-09

一、Mybatis映射文件

1、映射文件根標簽

mapping標簽：

該標簽中的namespace要求與介面的全類名一致

2、映射文件子標簽

（1）cache（該命名空間的緩衝配置）

（2）cache-ref（引用其他命名空間的緩存配置）

（3）resultMap（描述如何從資料庫結果集中載入對象，是最複雜也是最強大的元素）

註意：resultType解決不了的問題，交給resultMap（一般是多表查詢）。

（4）sql（可被其他語句引用的可重用語句塊）

（5）insert（映射插入語句）

（6）update（映射更新語句）

（7）delete（映射刪除語句）

（8）select（映射查詢語句）

3、示例代碼

（1）“day02_mybatis.src.main.java.com.hh.mybatis.mapper.EmployeeMapper”中的代碼

package com.hh.mybatis.mapper;

import com.hh.mybatis.pojo.Employee;

import java.util.List;

public interface EmployeeMapper {
    /**
     * 通過id獲取員工信息
     * @param empId
     * @return
     */
    public Employee selectEmployee(int empId);

    /**
     * 添加員工信息
     * @param employee
     */
    public void insertEmployee(Employee employee);

    /**
     * 刪除員工信息
     * @param empId
     */
    public void deleteEmployeeById(int empId);

    /**
     * 修改員工信息
     * @param employee
     */
    public void updateEmployee(Employee employee);

    /**
     * 查詢所有員工信息
     * @return
     */
    public List<Employee> selectAllEmps();
}

（2）映射文件中的代碼（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）測試類代碼（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);
            //通過sqlSessionFactory獲取sqlSession對象
            SqlSession sqlSession = sqlSessionFactory.openSession();
            //獲取EmployeeMapper的代理對象
            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();
        }
    }

    /**
     * 測試添加員工
     */
    @Test
    public void TestMybatisInsert(){
        try {
            String resource = "mybatis-config.xml";
            InputStream inputStream = Resources.getResourceAsStream(resource);
            SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
            //通過sqlSessionFactory獲取sqlSession對象
            SqlSession sqlSession = sqlSessionFactory.openSession();
            //獲取EmployeeMapper的代理對象
            EmployeeMapper employeeMapper = sqlSession.getMapper(EmployeeMapper.class);

//            Employee wangwu = new Employee(null,"wangwu","[email protected]",50.0);

            //測試添加員工信息
//            employeeMapper.insertEmployee(wangwu);

            //測試刪除員工信息
//            employeeMapper.deleteEmployeeById(2);

//            Employee wangwu = new Employee(1,"zhangsan1","[email protected]",102.0);
//
//            employeeMapper.updateEmployee(wangwu);

            //查詢所有員工信息
            List<Employee> employees = employeeMapper.selectAllEmps();
            for (Employee employee : employees) {
                System.out.println("employee = " + employee);
            }
            //提交事務
            sqlSession.commit();

        } catch (IOException e) {
            e.printStackTrace();
        }
    }

}