MyBatis快速上手及理解

MyBatis是什么？

MyBatis是一款优秀的持久层框架，用于简化JDBC开发，MyBatis是阿帕奇的一个框架。

持久层
负责将数据保存的那一层代码
JavaEE三层架构：表现层、业务层，持久层

框架
框架就算一个半成品的软件，是一套可用的、通用的、软件基础代码模型。
在框架的基础之上构建软件编写更加高效。

第一步创建maven项目
第二步从maven仓库导入mybatis依赖和mysql链接依赖

User.class

package pojo;

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

    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 String getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;
    }

    public String getAddr() {
        return addr;
    }

    public void setAddr(String addr) {
        this.addr = addr;
    }

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

dome.class

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 pojo.User;

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

import java.util.List;

public class dome {
    public static void main(String[] args) throws IOException {
        //1.加载mybatis的核心配置文件，获取sqlsessionFactary
        String resource = "mybatis-config.xml";
        InputStream inputStream =Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        //2.获取SqlSessionFactory对象
        SqlSession sqlSession =sqlSessionFactory.openSession();
        //3.执行sql语句
        List<User> users=sqlSession.selectList("User.selectAll");

        //打印结构
        System.out.println(users);

        //释放资源
        sqlSession.close();

    }
}

resources
mybatis-config.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "https://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="jdbc:mysql:///mybatis?use"/>
                <property name="username" value="root"/>
                <property name="password" value="123456"/>
            </dataSource>
        </environment>
    </environments>
<!--    用于指定当前sql文件的映射文件路径-->
    <mappers>
        <mapper resource="UserMapper.xml"/>
    </mappers>
</configuration>

UserMapper.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<!--        namespace名称空间-->
<mapper namespace="User">
<!--    id是sql语句对应的值，resultType是返回类型-->
    <select id="selectAll" resultType="pojo.User">
        select * from tb_user;
    </select>

</mapper>

mapper代理

resources 下面创建同目录接口的xml。
主方法

import mapper.UserMapper;
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 pojo.User;

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

public class dome2 {
    public static void main(String[] args) throws IOException {
        //1.加载mybatis的核心配置文件，获取sqlsessionFactary
        String resource = "mybatis-config.xml";
        InputStream inputStream =Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        //2.获取SqlSessionFactory对象
        SqlSession sqlSession =sqlSessionFactory.openSession();
        //3.执行sql语句
//        List<User> users=sqlSession.selectList("User.selectAll");

        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        List <User> users= userMapper.selectAll();


        //打印结构
        System.out.println(users);

        //释放资源
        sqlSession.close();

    }
}

实现代理