Java持久化ORM框架

JDBC操作数据库步骤 (以查询为例)

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MyBatis示例

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<?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">
            <!-- 配置事务管理器的类型 -->
            <transactionManager type="JDBC"/>
            <!-- 配置数据源的类型，以及数据库连接的相关信息 -->
            <dataSource type="POOLED">
                <!-- 数据库的链接信息-->
                <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql:///mybatis?useSSL=false&amp;zeroDateTimeBehavior=convertToNull&amp;useTimezone=true&amp;serverTimezone=GMT%2B8"/>
                <property name="username" value="root"/>
                <property name="password" value="mt980312"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <!-- 加载sql的映射文件 -->
        <mapper resource="UserMapper.xml"/>
    </mappers>
</configuration>
  • 了解了mybatis-config.xml配置文件的大致结构之后，来看一下UserMapper.xml映射配置文件的结构，代码如下：
<?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：名称空间
-->

<!-- 定义SQL 语句，除了select 节点，还可以定义insert, 
update 、delete 节点。为了便于描述，后面统称为“ SQL 节点” -->

<mapper namespace="test">
    <select id="selectAll" resultType="com.itheima.User">
        select * from tb_user where;
    </select>
</mapper>

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package com.itheima;


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


import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

/**
 * @author mengtong5
 * @description Mybatis快速入门代码
 * @date 2022/8/9
 */
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，用它来执行sql
        SqlSession sqlSession = sqlSessionFactory.openSession();

        //3.执行sql
        List<User> Users = sqlSession.selectList("test.selectAll");

        //4.打印查询数据
        System.out.println(Users);

        //5.释放资源
        sqlSession.close();
    }
}

  • 映射实体类 alt

  • 表结构 alt

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