第一节

1.1什么是MyBatis

? MyBatis本是apache的一个开源项目iBatis,2010年因为迁移，改名为MyBatis,一款优秀的持久层框架
? 支持定制化SQL、存储过程以及高级映射
? MyBatis避免了几乎所有的JDBC代码和手动设置的参数以及获取结果集
? MyBatis可以使用简单的XML或注解来配置和映射原生类、接口和java的POJO（Plain Old java Objects,普通老式对象）为数据库中的记录

1.2获取MyBatis

? 从maven仓库获取

<dependency>
    <groupId>org.mybatis</groupId>
    <artifactId>mybatis</artifactId>
    <version>3.5.7</version>
</dependency>

1.3什么是持久化

? 就是将程序的数据在持久态和瞬时态转化的过程
? 为了对象不丢失，所以要持久化

1.4什么是持久层

? Dao层、Service层、Controller.

1.5为什么需要MyBatis

? 方便，帮助我们将数据存入数据库、简单易学、sql和代码分离，提高了可维护性
? 传统的JDBC代码太复杂

第二节

2.1MyBatis入门使用

2.1.1建立数据库

create database mybatis;
use mybatis;
create table MyBatis(

`id` int(20) not null,
`name` varchar(32) default null,
`pwd` varchar(32) default null)engine = innodb default charset = utf8;
insert into `MyBatis` (`id`,`name`,`pwd`) values
(1,'898717454','898717454'),
(2,'209053771','209053771'),
(3,'13140662112','13140662112'),
(4,'2251231008','2251231008'),
(5,'13526260059','13526260059');


select * from Mybatis;

2.1.2创建一个普通的maven项目

2.1.2删除src

这里删除src后去配置pom文件这个pom文件作为父模块中的pom文件，这样的好处是子项目不用每次都配置pom文件了

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.polarBear</groupId>
    <artifactId>MyBatis-Study</artifactId>
    <packaging>pom</packaging>
    <version>1.0-SNAPSHOT</version>

<!--这是删除src后创建项目后生成的代码块，意思是他有一个子模块，他们共享一个pom文件-->
    <modules>
        <module>mybatis-Demo01</module>
    </modules>

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
    </properties>

    <!--导入依赖-->
    <dependencies>
        <!--mysql驱动-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.26</version>
        </dependency>

        <!--mybatis-->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.7</version>
        </dependency>

        <!--junit-->
        <dependency>
            <groupId>org.junit.jupiter</groupId>
            <artifactId>junit-jupiter-api</artifactId>
            <version>5.8.0-RC1</version>
            <scope>test</scope>
        </dependency>




    </dependencies>

</project>

2.1.3导入maven依赖

mysql驱动、MyBatis依赖、junit依赖

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.polarBear</groupId>
    <artifactId>MyBatis-Study</artifactId>
    <version>1.0-SNAPSHOT</version>

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
    </properties>

    <!--导入依赖-->
    <dependencies>
        <!--mysql驱动-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.26</version>
        </dependency>

        <!--mybatis-->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.7</version>
        </dependency>

        <!--junit-->
        <dependency>
            <groupId>org.junit.jupiter</groupId>
            <artifactId>junit-jupiter-api</artifactId>
            <version>5.8.0-RC1</version>
            <scope>test</scope>
        </dependency>




    </dependencies>

</project>

2.1.4创建一个模块

2.1.4.1编写Mybatis的核心配置文件

<?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核心配置文件-->
<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://localhost:3306/mybatis?useSSl=true&amp;useUnicode=true&amp;characterEncoding=UTF-8"/>
            <property name="username" value="root"/>
            <property name="password" value="123abcABC"/>
                
            </dataSource>

        </environment>
    </environments>

</configuration>

2.1.4.2编写Mybatis工具类

package com.polarbear.utils;


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.io.InputStream;

public class MybatisUtils {
    private static SqlSessionFactory sqlSessionFactory;
    static {
        try {
            //使用Mybatis第一步要获取sqlSessionFactory对象
            String resource = "mybatis-config.xml";
            InputStream inputStream = Resources.getResourceAsStream(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    public static SqlSession getSqlSession(){
        return sqlSessionFactory.openSession();
    }
}

2.1.5编写代码

? 可能遇到的问题

配置文件没有注册-在mybatis核心配置中
绑定接口错误
方法名不对
返回类型不对
Maven导出资源问题-在pom文件中

2.1.5.1实体类

package com.polarbear.pojo;
//实体类
public class User {
    private int id;
    private String name;
    private String pwd;

    public User() {
    }

    public User(int id, String name, String pwd) {
        this.id = id;
        this.name = name;
        this.pwd = pwd;
    }

    public int getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getPwd() {
        return pwd;
    }

    public void setPwd(String pwd) {
        this.pwd = pwd;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", pwd='" + pwd + '\'' +
                '}';
    }
}

2.1.5.2Dao接口

package com.polarbear.dao;

import com.polarbear.pojo.User;

import java.util.List;

public interface UserDao {
    List<User> getUserList();
    
    
}

2.1.5.3接口实现类

<?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">
<!--namespace=绑定一个对应的Dao/mapper接口-->
<mapper namespace="com.polarbear.dao.UserDao">

    <!--select查询语句-->
    <select id="getUserList" resultType="com.polarbear.pojo.User">
        select * from mybatis.user
    </select>

</mapper>

2.1.5.4测试

2.1.5.4.1Mybatis核心文件中注册mappers

<?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核心配置文件-->
<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://localhost:3306/mybatis?useSSl=true&amp;useUnicode=true&amp;characterEncoding=UTF-8"/>
            <property name="username" value="root"/>
            <property name="password" value="123abcABC"/>

            </dataSource>

        </environment>
    </environments>

    <!--每一个Mapper.XML都需要在Mybatis核心配置文件中注册-->
    <mappers>
        <mapper resource="com/polarbear/dao/UserMapper.xml"/>
    </mappers>
</configuration>

2.1.5.4.2在pom文件中配置resources

所有的maven项目首先一上来就完成这样的配置

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.polarBear</groupId>
    <artifactId>MyBatis-Study</artifactId>
    <packaging>pom</packaging>
    <version>1.0-SNAPSHOT</version>
    <modules>
        <module>mybatis-Demo01</module>
    </modules>

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
    </properties>

    <!--导入依赖-->
    <dependencies>
        <!--mysql驱动-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.26</version>
        </dependency>

        <!--mybatis-->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.7</version>
        </dependency>

        <!--junit-->
        <dependency>
            <groupId>org.junit.jupiter</groupId>
            <artifactId>junit-jupiter-api</artifactId>
            <version>5.8.0-RC1</version>
            <scope>test</scope>
        </dependency>

    </dependencies>

    <!--在build中配置resources,来防止我们资源道出失败的问题-->
    <build>
        <resources>
            <resource>
                <directory>src/main/resources</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>true</filtering>
            </resource>
            <resource>
                <directory>src/main/java</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>true</filtering>
            </resource>
        </resources>

    </build>

</project>

2.1.5.4.3测试代码

package com.polarbear.dao;

import com.polarbear.pojo.User;
import com.polarbear.utils.MybatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;
import java.util.List;

public class UserDaoTest {

    @Test
    public void test(){
        //第一步：获取SqlSession对象
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        //方式一：getMapper
        UserDao userDao = sqlSession.getMapper(UserDao.class);
        List<User> userList = userDao.getUserList();
        for (User user : userList){
            System.out.println(user);
        }

        //关闭SqlSession
        sqlSession.close();

    }

}