mybatis - 初识mybatis

一、mybatis环境搭建

mybatis核心配置文件,  文件名为 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>

    <!--设置连接数据库的环境-->
    <environments default="development">
    
   
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${driver}"/>
                <property name="url" value="${url}"/>
                <property name="username" value="${username}"/>
                <property name="password" value="${password}"/>
            </dataSource>
        </environment>
    </environments>
    
    <!--引入映射文件-->
    <mappers>
        <!-- 配置映射文件路径 -->
        <mapper resource="mappers/userMapper.xml"/>
    </mappers>
    
</configuration>

创建数据库

create database t_userDB;

use t_userDB;

create table t_user(
    id int primary key auto_increment,
    username varchar(30) not null ,
    password varchar(30) not null
);

insert into t_user(username,password) values
('test01','test01'),('admin','admin');

select * from t_user;

根据数据库中的表字段，创建对应的实体类

public class User {
    private Integer id;
    private String username;
    private String password;


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

    public Integer getId() {
        return id;
    }

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

    public String getUsername() {
        return username;
    }

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

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public User() {
    }

    public User(Integer id, String username, String password) {
        this.id = id;
        this.username = username;
        this.password = password;
    }
}

创建mapper接口，mapper接口相当于之前的dao接口。只不过不创建实现类

public interface UserMapper {

    int addUser();
}

创建映射文件

<?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 :  要操作的mapper接口 -->
<mapper namespace="com.xin.mybatis.mappers.UserMapper">
<!--     int addUser();       -->
  <!-- id : 要和接口中的方法一致  -->
        <insert id="addUser">
            insert into t_user values(null,'张三','123456')
        </insert>
</mapper>

测试添加用户方法

@Test
public void testAddUser() throws IOException {
        // 1. 读取mybatis核心配置文件
        InputStream is = Resources.getResourceAsStream("mybatis-config.xml");

        // 2. 创建SpringSessionFactory
        SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(is);

        // 3. 通过工厂类来创建 sqlSession对象
        // openSession()   来创建sqlSession对象
        SqlSession sqlSession = factory.openSession();

        // 4.getMapper() 通过代理模式来创建实现类
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        userMapper.addUser();

        // 5.提交sql语句
        sqlSession.commit();

    }

对应规则 

1.表字段与实体类属性对应

2.mapper接口中的方法与映射文件中的id对应