Mybatis快速入门Demo

1：导入mybatis相关jar

2：编写Mybatis配置文件(mybatis.xml 名字任意取都行) (最主要的配置 连接数据库 和关联 实体与数据库的映射文件)

<?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>

    <!-- 加载Src下的配置文件   -->
    <properties resource="db.properties"/>
    <!--别名机制-->
    <typeAliases>
        <typeAlias type="com.cn.entity.User" alias="user"/>
    </typeAliases>

    <!-- 连接mysql数据库   -->
    <environments default="mysql_development">
        <environment id="mysql_development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${driverClass}"/>
                <property name="url" value="${jdbcUrl}"/>
                <property name="username" value="${user}"/>
                <property name="password" value="${password}"/>
            </dataSource>
        </environment>

        <!--  连接Oracle数据库  -->
        <environment id="oracle_development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="oracle.jdbc.driver.OracleDriver"/>
                <property name="url" value="jdbc:oracle:thin:localhost:1521:orcl"/>
                <property name="username" value="${user}"/>  <!--value的值 相当于mysql的数据库的名 在oracle中就是登陆的用户-->
                <property name="password" value="${password}"/>
            </dataSource>
        </environment>

</environments>

    <!-- 加载映射文件   -->
    <mappers>
        <mapper resource="com/cn/entity/mybatisUserMapper.xml"/>
    </mappers>
    
</configuration>

3编写实体bean 字段尽量与数据库中的表对应

public class User {

    private int id;
    private String username;
    private Date birthday;
    private String sex;
    private String address;

    ....省get set....  
}

4实体与数据库的映射文件

<?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" >



<mapper namespace="com.cn.entity.User" >

    <!--一个resultmap相当与一张数据表与实体的设 当实体与数据库表字段不一直时需要配置-->
<!--    <resultMap id="accountResultMap" type="account" >-->
<!--        <id column="acc_id" property="accId" jdbcType="INTEGER" />-->
<!--        <result column="acc_login" property="accLogin" jdbcType="VARCHAR" />-->
<!--        <result column="acc_name" property="accName" jdbcType="VARCHAR" />-->
<!--        <result column="acc_pass" property="accPass" jdbcType="VARCHAR" />-->
<!--    </resultMap>-->

    <!--用户登录-->
    <select id="findAll" resultType="user" >
        select  * from user;
  </select>

</mapper>

5测试的app

public class TestApp {
    public static void main(String[] args) {
        try {

            /*
                加载资源的一种方式：
                InputStream in = Resources.getResourceAsStream("mybatis.xml");
                //创建SqlSessionFactory
                SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(in);
                SqlSession sqlSession = sqlSessionFactory.openSession();
                System.out.println(sqlSession);
            */
            SqlSession sqlSession = MyBatisUtil.getSqlSession();
            List<User> list = sqlSession.selectList("com.cn.entity.User.findAll");
            for(User u :list){
                System.out.println(u);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}


结果：

User{id=1, username='zhangsan', birthday=Mon Feb 05 00:00:00 CST 2018, sex='男', address='湖南'}
User{id=2, username='rose', birthday=Thu Mar 08 00:00:00 CST 2018, sex='女', address='东莞'}
User{id=3, username='black', birthday=Fri Feb 19 00:00:00 CST 2021, sex='男', address='深圳'}
User{id=4, username='pink_girl', birthday=Sat Aug 24 00:00:00 CST 2019, sex='女', address='changsan'}
User{id=8, username='heheh', birthday=Sat Aug 24 00:00:00 CST 2019, sex='女', address='huana'}