1. 简介

mybatis是一款优秀的持久层框架，用来简化JDBC开发

持久层：负责将数据保存到数据库的那一层代码

2. 简单使用

依赖

<dependencies>  
        <dependency>            
	        <groupId>org.mybatis</groupId>  
            <artifactId>mybatis</artifactId>  
            <version>3.5.14</version>  
        </dependency><!--        mysql的驱动-->  
        <dependency>  
            <groupId>mysql</groupId>  
            <artifactId>mysql-connector-java</artifactId>  
            <version>5.1.26</version>  
        </dependency>        
        <dependency>            
	        <groupId>junit</groupId>  
            <artifactId>junit</artifactId>  
            <scope>test</scope>  
            <version>4.13.2</version>  
        </dependency>    
    </dependencies>

<?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>  
    <environments default="development">  
        <environment id="development">  
            <transactionManager type="JDBC"/>  
            <dataSource type="POOLED">  
                <property name="driver" value="com.mysql.jdbc.Driver"/>  
                <property name="url" value="${url}"/>  
                <property name="username" value="${username}"/>  
                <property name="password" value="${password}"/>  
            </dataSource>        </environment>    </environments>    <mappers>        <mapper resource="org/mybatis/example/BlogMapper.xml"/>  
    </mappers></configuration>

Userx

package com.yxz.pojo;  
  
import java.util.Date;  
  
public class Userx {  
    private Integer id;  
    private String username;  
    private Date birthday;  
    private Character sex;  
    private String address;  
  
    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 Date getBirthday() {  
        return birthday;  
    }  
  
    public void setBirthday(Date birthday) {  
        this.birthday = birthday;  
    }  
  
    public Character getSex() {  
        return sex;  
    }  
  
    public void setSex(Character sex) {  
        this.sex = sex;  
    }  
  
    public String getAddress() {  
        return address;  
    }  
  
    public void setAddress(String address) {  
        this.address = address;  
    }  
  
    @Override  
    public String toString() {  
        return "Userx{" +  
                "id=" + id +  
                ", username='" + username + '\'' +  
                ", birthday=" + birthday +  
                ", sex=" + sex +  
                ", address='" + address + '\'' +  
                '}';  
    }  
}

UserMapper.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="test">  
  
    <select id="selectAll" resultType="com.yxz.pojo.Userx">  
        select * from userx;  
    </select>  
</mapper>

进行测试：

package com.yxz;  
  
import com.yxz.pojo.Userx;  
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.IOException;  
import java.io.InputStream;  
import java.util.List;  
  
public class MybatisDemo {  
    public static void main(String[] args) throws IOException {  
        // 1. 加载mybatis的核心配置文件，获取SqlSessionFactory  
        String resource = "mybatis-config.xml";  
        InputStream inputStream = Resources.getResourceAsStream(resource);  
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);  
  
        // 2. 获取对应的SqlSession对象，用它执行sql  
        SqlSession sqlSession = sqlSessionFactory.openSession();  
  
        // 3. 执行sql  
        List<Userx> userxs =  sqlSession.selectList("test.selectAll");  
        System.out.println(userxs);  
        sqlSession.close();  
    }  
}

建好数据库

目录：

3. 代理开发

创建一个接口，作为代理

package com.yxz.dao;  
  
import com.yxz.pojo.Userx;  
  
import java.util.List;  
  
public interface UserMapper {  
  
    List<Userx> selectAll();  
}

命名空间修改：

<?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.yxz.dao.UserMapper">  
  
    <select id="selectAll" resultType="com.yxz.pojo.Userx">  
        select * from userx;  
    </select>  
</mapper>

进行测试

package com.yxz;  
  
import com.yxz.dao.UserMapper;  
import com.yxz.pojo.Userx;  
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.IOException;  
import java.io.InputStream;  
import java.util.List;  
  
public class MybatisDemo {  
    public static void main(String[] args) throws IOException {  
        // 1. 加载mybatis的核心配置文件，获取SqlSessionFactory  
        String resource = "mybatis-config.xml";  
        InputStream inputStream = Resources.getResourceAsStream(resource);  
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);  
  
        // 2. 获取对应的SqlSession对象，用它执行sql  
        SqlSession sqlSession = sqlSessionFactory.openSession();  
  
        // 3. 执行sql  
//        List<Userx> userxs =  sqlSession.selectList("test.selectAll");  
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);  
        List<Userx> userxs =  userMapper.selectAll();  
        System.out.println(userxs);  
        sqlSession.close();  
    }  
}

4. 小技巧

起别名

<typeAliases>  
    <package name="com.yxz.pojo"/>  
</typeAliases>

<select id="selectAll" resultType="userx">  
    select  
    <include refid="brand_column"/>  
    from userx;  
</select>  
<sql id="brand_column">  
    id,username, birthday, sex, address  
</sql>

<select id="selectById" parameterType="int" resultType="userx">  
    select  
    <include refid="brand_column"/>  
    from userx where id  
     <![CDATA[        <     ]]>     #{id};</select>

5. 动态查询

choose when otherwise
set if

delete from user where id 
in(<foreach collction="ids" item="id" separator=",">#{id} </foreach>) ;

6. 注解（待更新）

@Select
@Insert
@Update
@Delete

底部