MyBatis·上

已于 2025-03-20 20:44:31 修改
阅读量635 收藏 17
点赞数 22
分类专栏： Spring 文章标签： mybatis java spring
于 2025-03-13 16:04:50 首次发布
版权声明：本文为博主原创文章，遵循 CC 4.0 BY-SA 版权协议，转载请附上原文出处链接和本声明。
本文链接：https://blog.youkuaiyun.com/Tttian622/article/details/146222280
版权

一、MyBatis 简介

MyBatis 用于持久层（dao）框架，持久层是对数据库进行操作的部分，前版本iBatis，由Apache软件基金组织进行更名并维护。

特点：

1、简化数据库的操作  2、SQL映射灵活（半ORM框架，ORM：对象与映射的关系）

3、支持高级映射  4、易于集成维护  5、配置动态SQL  6、提供缓存机制

功能：

替代JDBC（JDBC：Java中提供，用于操作数据库的技术及方案）

JDBC缺点与Batis解决方案：

        1、数据库的连接控制难。→连接池

        2、SQL语句硬编码。→将SQL语句放置到xml配置文件中

        3、参数传递问题。→提供类型适配器

        4、返回值问题。→响应对象注入

总结：

1、MyBatis让程序开发者的工作聚焦在业务层面，而不是SQL处理的层面。

2、解决数据格式抗拒不匹配的问题

二、POM(项目对象模型)配置

    <dependencies>
        <!-- mysql驱动  -->
        <dependency>
            <groupId>com.mysql</groupId>
            <artifactId>mysql-connector-j</artifactId>
            <version>8.0.33</version>
        </dependency>
        <!-- mybatis驱动 -->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.2</version>
        </dependency>
        <!-- junit驱动 -->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
        </dependency>
    </dependencies>

三、封装用户信息

package org.example.pojo;
import java.util.Date;

public class User {
    private int id;
    private String username;
    private String sex;
    private Date birthday;
    private String address;

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    public Date getBirthday() {
        return birthday;
    }

    public void setBirthday(Date birthday) {
        this.birthday = birthday;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", sex='" + sex + '\'' +
                ", birthday=" + birthday +
                ", address='" + address + '\'' +
                '}';
    }
}

四、MyBatis 执行原理

映射文件UserMapper.xml、映射类User.java

1.加载MyBatis主配置文件

文件地址：src/main/resources/SqlMapConfig.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">
<!--数据库连接相关配置-->
<configuration>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://127.0.0.1:3306/mybatis"/>
                <property name="username" value="root"/>
                <property name="password" value="888888"/>
            </dataSource>
        </environment>
    </environments>
<!--关联映射配置文件-->
    <mappers>
        <mapper resource="UserMapper.xml"></mapper>
    </mappers>
</configuration>

  • 2.运行环境

包括数据库连接池、事务管理、加载配置文件

文件地址：src/main/resources/UserMapper.xml

  • namespace：命名空间。通常用于在Java程序中调用该配置文件的标识
  • select：表示执行查询语句
  • id：该标记的唯一值通常与Java程序中的接口名一致
  • parameter：传入参数的数据类型
  • resultType：返回查询结果的数据类型在select标记中编写SQL语句，#{id}表示接受参数的位置
<?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="test">
    <select id="findUserById" parameterType="int" resultType="org.example.pojo.User">
        select * from user where id=#{id}
    </select>
</mapper>

3.创建并获得会话

文件地址：src/test/java/MyBatisTest.java

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.example.pojo.User;
import org.junit.Test;

import java.io.IOException;
import java.io.InputStream;

public class MyBatisTest {
    @Test
    public void findUserByIdTest() throws IOException {
        //加载MyBatis配置文件
        String resource = "SqlMapConfig.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        //根据主配置文件创建会话工厂
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        //通过会话工厂获得会话
        SqlSession sqlSession = sqlSessionFactory.openSession();
        //通过会话对象对数据库进行查询
        //参数1：获得查询标记的位置 ; 参数2：查询条件
        User user = sqlSession.selectOne("test.findUserById",1);
        System.out.println(user);
        //关闭会话连接
        sqlSession.close();
    }
}

四、增删改查

1.根据用户名模糊查询用户信息

文件地址：src/main/resources/UserMapper.xml

${}：表示sqL拼接，将参数直接拼接到sql中。注意，该写法容易引起sqL注入的问题，如果是简单类型，只能使用value。

#{}：表示占位符(通配符),常用,不会进行sql拼接。可以规避sqL注入问题,{}中必须与对象的属性一致。 

<select id="findUserByName" parameterType="String" resultType="org.example.pojo.User">
    select * from user where username like '%${value}%'
</select>

 文件地址：src/test/java/MyBatisTest.java

@Test
public void findUserByNameTest() throws IOException {
    String resource = "SqlMapConfig.xml";
    InputStream inputStream = Resources.getResourceAsStream(resource);
    SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    SqlSession sqlSession = sqlSessionFactory.openSession();
        List<User> list = sqlSession.selectList("test.findUserByName","四");
        System.out.println(list);
        sqlSession.close();
}

2. 添加用户信息

获得新增ID，select last_insert_id()获得最新添加的id,keyProperty对象的属性名，

order执行添加之后获得id,resultType返回id值的类型

<insert id="insertUser" parameterType="org.example.pojo.User">
    <selectKey keyProperty="id" order="AFTER" resultType="java.lang.Integer">
        select last_insert_id()
    </selectKey>
    insert into user(username,birthday,sex,address) values (#{username},#{birthday},#{sex},#{address})
</insert>
@Test
public void insertUserTest() throws IOException {
    String resource = "SqlMapConfig.xml";
    InputStream inputStream = Resources.getResourceAsStream(resource);
    SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    SqlSession sqlSession = sqlSessionFactory.openSession();
    //创建添加数据的实例
    User user = new User();
    user.setUsername("迪丽热巴");
    user.setBirthday(new Date());
    user.setSex("女");
    user.setAddress("新疆乌鲁木齐");
    //返回值是整形数字，表示对数据库操作了几行数据
    int i = sqlSession.insert("test.insertUser",user);
    System.out.println(i);
    System.out.println(user.getId());
    //提交数据
    sqlSession.commit();
    sqlSession.close();
}

 3.删除用户信息

<delete id="deleteUser" parameterType="java.lang.Integer">
    delete from user where id=#{id}
</delete>
@Test
public void deleteUserTest() throws IOException {
    String resource = "SqlMapConfig.xml";
    InputStream inputStream = Resources.getResourceAsStream(resource);
    SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    SqlSession sqlSession = sqlSessionFactory.openSession();
    int i = sqlSession.delete("test.deleteUser",31);
    System.out.println(i);
    sqlSession.commit();
    sqlSession.close();
}

4. 修改用户信息

<update id="updateUser" parameterType="org.example.pojo.User">
    update user set username=#{username},birthday=#{birthday},sex=#{sex},address=#{address}
    where id=#{id}
</update>
@Test
public void updateUserTest() throws IOException {
    String resource = "SqlMapConfig.xml";
    InputStream inputStream = Resources.getResourceAsStream(resource);
    SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    SqlSession sqlSession = sqlSessionFactory.openSession();
    User user = new User();
    user.setId(32);
    user.setUsername("彭于晏");
    user.setBirthday(new Date());
    user.setSex("2");
    user.setAddress("大连市");
    int i = sqlSession.update("test.updateUser",user);
    System.out.println(i);
    sqlSession.commit();
    sqlSession.close();
}

五、使用映射器(Mapper)代理的方式实现对数据库操作

1.创建接口

文件地址：org/example/mapper/UserMapper.java

package org.example.mapper;
import org.example.pojo.User;
import java.util.List;
public interface UserMapper {
    public User selectUserById(int id);
    public List<User> selectUserByName(String name);
    public int insertUser(User user);
    public int deleteUser(int id);
    public int updateUser(User user);
}

2.映射文件

文件地址：src/main/resources/UserMapper.xml

无差别，注意自己起的函数名就好。

3.实现类

文件地址：src/test/java/UserMapperTest.java

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.example.mapper.UserMapper;

import org.example.pojo.User;
import org.junit.Test;

import java.io.IOException;
import java.io.InputStream;
import java.util.Date;
import java.util.List;

public class UserMapperTest {
    @Test
    public void selectUserByIdTest() throws IOException {
        String resource = "SqlMapConfig.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        SqlSession sqlSession = sqlSessionFactory.openSession();
        //代理对象的内部会根据返回值类型自动调用selectOne或selectList完成数据查询
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        User user = userMapper.selectUserById(1);
        System.out.println(user);
        sqlSession.close();
    }

    @Test
    public void findUserByNameTest() throws IOException {
        String resource = "SqlMapConfig.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        SqlSession sqlSession = sqlSessionFactory.openSession();
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        List<User> user = userMapper.selectUserByName("四");
        System.out.println(user);
        sqlSession.close();
    }

    @Test
    public void insertUser() throws IOException {
        String resource = "SqlMapConfig.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        SqlSession sqlSession = sqlSessionFactory.openSession();
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        User user = new User();
        user.setUsername("普京");
        user.setBirthday(new Date());
        user.setSex("男");
        user.setAddress("莫斯科");
        UserMapper userMapper1 = sqlSession.getMapper(UserMapper.class);
        int insertNum = userMapper1.insertUser(user);
        System.out.println(insertNum);
        sqlSession.commit();
        sqlSession.close();
    }
    @Test
    public void deleteUserTest() throws IOException {
        String resource = "SqlMapConfig.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        SqlSession sqlSession = sqlSessionFactory.openSession();
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        int i = userMapper.deleteUser(33);
        System.out.println(i);
        sqlSession.commit();
        sqlSession.close();
    }
    @Test
    public void updateUserTest() throws IOException {
        String resource = "SqlMapConfig.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        SqlSession sqlSession = sqlSessionFactory.openSession();
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        User user = new User();
        user.setId(32);
        user.setUsername("蔡徐坤");
        user.setBirthday(new Date());
        user.setSex("男");
        user.setAddress("大连市");
        int updateNum = userMapper.updateUser(user);
        System.out.println(updateNum);
        sqlSession.commit();
        sqlSession.close();
    }

}
评论
添加红包

请填写红包祝福语或标题

个

红包个数最小为10个

元

红包金额最低5元

当前余额3.43元 前往充值 >
需支付：10.00元
成就一亿技术人!
领取后你会自动成为博主和红包主的粉丝 规则
hope_wisdom
发出的红包
实付元
使用余额支付
点击重新获取
扫码支付
钱包余额 0

抵扣说明：

1.余额是钱包充值的虚拟货币，按照1:1的比例进行支付金额的抵扣。
2.余额无法直接购买下载，可以购买VIP、付费专栏及课程。

余额充值