MyBatis框架详解

最新推荐文章于 2023-01-07 11:28:41 发布

「已注销」

最新推荐文章于 2023-01-07 11:28:41 发布

阅读量358

点赞数

分类专栏：初识MyBatis框架文章标签： java

本文链接：https://blog.youkuaiyun.com/weixin_49588744/article/details/109501709

版权

初识MyBatis框架专栏收录该内容

1 篇文章

订阅专栏

本文详细介绍了MyBatis框架，它是一个ORM数据访问层框架，简化了数据库访问操作，提高了开发效率。文章讨论了框架的本质，数据访问层的角色，以及为何选择MyBatis。还概述了ORM的概念，并提供了使用MyBatis开发用户信息系统的步骤。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

1.什么是MyBatis？
mybatis是一个基于ORM(对象关系映射)的数据访问层框架。

2.何为框架呢？
框架本质还是java程序，只不过框架是被一些牛人将原始及底层代码进行封装，将封装后的程序打包提供开发人员使用。帮助开发者提高开发的效率，同时也能提升项目的性能。
在这里插入图片描述
数据访问层–通常我们在做项目的时候，会把一个项目分成3个部分，这3个部分分别是：
2.1 控制层[web层]----用来做数据的导航【Servlet、Struts2、SpringMVC】
2.1 业务层----用来处理相关功能的具有实现业务。【Spring】
2.3 数据访问层[数据持久层]—用来访问数据库数据。【JDBC、Hibernate、MyBatis】
早期JavaWeb的3大框架—SSH[Struts2-Spring-Hibernate] 现在流行的JavaWeb的3大框架—SSM[SpringMVC-Spring-MyBatis]

3. 什么是ORM?
ORM—对象关系映射
我们在访问数据库的时候所编写的都是Java程序，Java程序只认识Java对象，而我们所访问的数据库大多数都是关系型数据库，那么这时Java程序要想访问关系型数据库，那么就需要将Java对象转换成关系型数据，才能被数据库认识。这时我们可以认为一个Java类就是关系型数据库中的一张数据表，Java类中的成员变量是数据库表中的一个列，Java类创建的Java对象就是数据库表中的一行记录。这时将Java对象对应成为数据库表记录的过程就是对象关系映射。
4. 为什么要使用MyBatis?
4.1 为了简化数据库访问操作，提高开发的效率，提升项目的性能，增加程序的可维护性。
4.2. 当我们使用Java程序控制Java对象的时候，数据库中的数据表记录会随之变化。(将原来通过java程序访问数据库表的操作，简化成通过java程序访问java对象)。

5.简单使用MyBatis框架开发一个用户信息系统
5.1 创建数据库表结构

create table tb_student(
stuid int primary key auto_increment,
stuname varchar(30),
stupassword varchar(20),
stuage int,
stuaddress varchar(30)
);

5.2 使用IDEA创建普maven项目，完善项目结构

5.3 pox.xml文件导入依赖

<!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
    <dependency>
      <groupId>mysql</groupId>
      <artifactId>mysql-connector-java</artifactId>
      <version>5.1.38</version>
    </dependency>
    <!-- https://mvnrepository.com/artifact/org.mybatis/mybatis -->
    <dependency>
      <groupId>org.mybatis</groupId>
      <artifactId>mybatis</artifactId>
      <version>3.4.6</version>
    </dependency>

5.4 根据数据库表结构创建java实体类

package com.qing.bean;

public class StudentBean {
    private int stuid;
    private String stuname;
    private String stupassword;
    private int stuage;
    private String stuaddress;

    public int getStuid() {
        return stuid;
    }

    public void setStuid(int stuid) {
        this.stuid = stuid;
    }

    public String getStuname() {
        return stuname;
    }

    public void setStuname(String stuname) {
        this.stuname = stuname;
    }

    public String getStupassword() {
        return stupassword;
    }

    public void setStupassword(String stupassword) {
        this.stupassword = stupassword;
    }

    public int getStuage() {
        return stuage;
    }

    public void setStuage(int stuage) {
        this.stuage = stuage;
    }

    public String getStuaddress() {
        return stuaddress;
    }

    public void setStuaddress(String stuaddress) {
        this.stuaddress = stuaddress;
    }
}

5.5 在src/main/resources中编写数据库资源文件 mydate.properties

mydriver = com.mysql.jdbc.Driver
myurl = jdbc:mysql://127.0.0.1:3306/test
myusername = root
mypassword = 123456

5.6 创建数据库访问接口

package com.qing.mapper;
import com.qing.bean.StudentBean;
import java.util.List;
public interface StudentMapper {
    //添加信息
    boolean insertStudent(StudentBean studentBean);

    //修改信息
    boolean updateStudentId(int stuid);

    //删除信息
    boolean deleteStudent(int stuid);

    //根据id查询
    StudentBean seleteStudentId(int stuid);

    //查询所有
    List<StudentBean> selectStudent();
}

5.7 在src/main/resources中编写sql映射文件 StudentMapper.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.qing.mapper.StudentMapper">
    <insert id="insertStudent" parameterType="com.qing.bean.StudentBean">
        insert into tb_student values (null,#{stuname},#{stupassword},#{stuage},#{stuaddress});
    </insert>
    <update id="updateStudent" parameterType="int">
        update tb_student set stuname=#{stuname},stupassword=#{stupassword},stuage=#{stuage},stuaddress=#{stuaddress} where stuid=#{stuid};
    </update>
    <delete id="deleteStudent" parameterType="int">
        delete from tb_student where stuid=#{stuid};
    </delete>
    <resultMap id="studentMap" type="com.qing.bean.StudentBean">
        <id column="stuid" property="stuid"></id>
        <result column="stuname" property="stuname"></result>
        <result column="stupassword" property="stupassword"></result>
        <result column="stuage" property="stuage"></result>
        <result column="stuaddress" property="stuaddress"></result>
    </resultMap>
    <select id="seleteStudentId" parameterType="int" resultMap="studentMap">
    select * from tb_student where stuid=#{stuid};
</select>
    <select id="selectStudent" resultMap="studentMap">
        select * from tb_student;
    </select>
</mapper>

5.8 在src/main/resources中创建 mybatis-config.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <!-- 配置引入数据连接字符串的资源文件 -->
    <properties resource="mydate.properties"></properties>
    <!-- 配置mybatis默认的连接数据库环境 -->
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"></transactionManager>
            <dataSource type="POOLED">
                <property name="driver" value="${mydriver}"></property>
                <property name="url" value="${myurl}"></property>
                <property name="username" value="${myusername}"></property>
                <property name="password" value="${mypassword}"></property>
            </dataSource>
        </environment>
    </environments>
    <!-- 配置mybatis数据访问接口的SQL映射文件路径 -->
    <mappers>
        <mapper resource="StudentMapper.xml"></mapper>
    </mappers>

</configuration>

5.9 测试

package com.qing.test;
import com.qing.bean.StudentBean;
import com.qing.mapper.StudentMapper;
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 java.util.List;
public class TestMain {
    /**
     * 添加信息
     */
    public static void insertStudent() {
        //定义SqlSession对象
        SqlSession sqlSession = null;
        try {
            //通过SqlSessionFactoryBuilder类创建出SqlSessionFactory对象
            SqlSessionFactory sqlSessionFactory = new
                    SqlSessionFactoryBuilder().build(Resources.getResourceAsReader("mybatis-config.xml"));
            //从SqlSessionFactory中取得一个SqlSession对象
            sqlSession = sqlSessionFactory.openSession();
            //通过数据访问接口调用添加方法
            StudentMapper studentMapper = sqlSession.getMapper(StudentMapper.class);
            StudentBean studentBean = new StudentBean();
            studentBean.setStuname("烤红薯");
            studentBean.setStupassword("111111");
            studentBean.setStuage(22);
            studentBean.setStuaddress("长丰国际");
            studentMapper.insertStudent(studentBean);
            sqlSession.commit();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            sqlSession.close();
        }
    }

    /**
     * 修改信息
     * @param stuid
     */
    public static void updateStudentId(int stuid) {
        SqlSession sqlSession = null;
        try {
            SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(Resources.getResourceAsReader("mybatis-config.xml"));
            sqlSession = sqlSessionFactory.openSession();
            StudentMapper studentMapper = sqlSession.getMapper(StudentMapper.class);
            StudentBean studentBean = new StudentBean();
            studentBean.setStuid(stuid);
            studentBean.setStuname("地瓜");
            studentBean.setStupassword("123321");
            studentBean.setStuage(122);
            studentBean.setStuaddress("曲江");
            studentMapper.updateStudentId(stuid);
            sqlSession.commit();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            sqlSession.close();
        }
    }

    /**
     * 删除信息
     * @param stuid
     */
    public static void deleteStudentId(int stuid) {
        SqlSession sqlSession = null;
        try {
            SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(Resources.getResourceAsReader("mybatis-config.xml"));
            sqlSession = sqlSessionFactory.openSession();
            StudentMapper studentMapper = sqlSession.getMapper(StudentMapper.class);
            StudentBean studentBean = new StudentBean();
            studentBean.setStuid(9);
            studentMapper.deleteStudent(stuid);
            sqlSession.commit();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            sqlSession.close();
        }
    }

    /**
     * 根据id查询信息
     * @param stuid
     */
    public static void selectStudentId(int stuid) {
        SqlSession sqlSession = null;
        try {
            SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(Resources.getResourceAsReader("mybatis-config.xml"));
            sqlSession = sqlSessionFactory.openSession();
            StudentMapper studentMapper = sqlSession.getMapper(StudentMapper.class);
            StudentBean studentBean = studentMapper.seleteStudentId(8);
            System.out.println(studentBean.getStuname() + "\t" + studentBean.getStuaddress());
            sqlSession.commit();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            sqlSession.close();
        }
    }

    /**
     * 查询所有信息
     */
    public static void selectStudent() {
        SqlSession sqlSession = null;
        try {
            SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(Resources.getResourceAsReader("mybatis-config.xml"));
            sqlSession = sqlSessionFactory.openSession();
            StudentMapper studentMapper = sqlSession.getMapper(StudentMapper.class);
            List<StudentBean> studentlist = studentMapper.selectStudent();
            for (StudentBean studentBean : studentlist) {
                System.out.println(studentBean.getStuname() + "\t" + studentBean.getStupassword() + "\t" + studentBean.getStuage() + "\t" + studentBean.getStuaddress());
            }
            sqlSession.commit();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            sqlSession.close();
        }
    }

    /**
     * 测试
     * @param args
     */
    public static void main(String[] args) {
        //insertStudent();
        updateStudentId(4);
        //deleteStudentId(9);
        //selectStudentId(8);
        //selectStudent();
    }
}