MyBatis快速入门(基础)

一：ORM介绍

1. 对象关系映射(Object Relational Mapping)
2. 持久化数据和实体对象的映射模式，为解决面向对象与关系型数据库存在的互不匹配的现象的技术
3. 映射规则：数据表对应类；表字段对应类属性；表数据对应对象

二：MyBatis介绍

1. MyBatis基于Java的持久层框架，封装了JDBC
2. MyBatis通过xml和注解的方式将要执行的各种Statement配置起来
3. MyBatis执行sql并将结果映射为java对象并放回，采用ORM思想解决了实体和数据库映射的问题

三：开发步骤

1. 添加MyBatis的jar包
2. 创建一个表
3. 编写表的实体类
4. 创建映射文件：StudentMapper.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="StudentMapper" >
    <select id="selectAll" resultType="com.hanjie.bean.Student">
        select * from student;
    </select>
</mapper>

5. 创建核心配置文件：MyBatisConfig.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>
    <environments default="mysql">
        <environment id="mysql">
            <transactionManager type="JDBC"></transactionManager>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/db14"/>
                <property name="username" value="root"/>
                <property name="password" value="自己的密码"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="StudentMapper.xml"/>
    </mappers>
</configuration>

6. 编写测试类

	public static void main(String[] args) throws Exception {
        //1.加载配置文件
        InputStream is = Resources.getResourceAsStream("MyBatisConfig.xml");
        //2.获取SqlSession工厂对象
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is);
        //3.通过SqlSession工厂对象获取SqlSession对象
        SqlSession sqlSession = sqlSessionFactory.openSession();
        //4.执行配置文件中sql语句，并接受结果
        List<Student> students = sqlSession.selectList("StudentMapper.selectAll");
        //5.处理结果集
        for (Student student:students) {
            System.out.println(student);
        }
        //6.释放资源
        sqlSession.close();
        is.close();
    }