MyBatis02快速入门

// 创建数据库
create database mybatis;
// 进入mybatis库中
use mybatis
// 建表
DROP TABLE IF EXISTS `tb_user`;
CREATE TABLE `tb_user` (
  `id` bigint(20) NOT NULL AUTO_INCREMENT,
  `user_name` varchar(100) DEFAULT NULL COMMENT '用户名',
  `password` varchar(100) DEFAULT NULL COMMENT '密码',
  `name` varchar(100) DEFAULT NULL COMMENT '名字',
  `age` int(10) DEFAULT NULL COMMENT '年龄',
  `sex` tinyint(1) DEFAULT NULL COMMENT '性别',
  `birthday` date DEFAULT NULL COMMENT '生日',
  `created` datetime DEFAULT NULL COMMENT '创建时间',
  `updated` datetime DEFAULT NULL COMMENT '更新时间',
  PRIMARY KEY (`id`),
  UNIQUE KEY `username` (`user_name`)
) ENGINE=InnoDB AUTO_INCREMENT=16 DEFAULT CHARSET=utf8;

// 插入一些数据
INSERT INTO `tb_user` VALUES ('1', 'zhangsan', 'zhangsan', '张三', '102', '1', '1984-08-08', '2014-09-19 16:56:04', '2018-11-13 13:17:41');
INSERT INTO `tb_user` VALUES ('2', 'lisi', '123456', '李四', '21', '2', '1991-01-01', '2014-09-19 16:56:04', '2014-09-19 16:56:04');
INSERT INTO `tb_user` VALUES ('3', 'wangwu', '123456', '王五', '22', '2', '1989-01-01', '2014-09-19 16:56:04', '2014-09-19 16:56:04');
INSERT INTO `tb_user` VALUES ('4', 'zhangwei', '123456', '张伟', '20', '1', '1988-09-01', '2014-09-19 16:56:04', '2014-09-19 16:56:04');
INSERT INTO `tb_user` VALUES ('5', 'lina', '123456', '李娜', '28', '1', '1985-01-01', '2014-09-19 16:56:04', '2014-09-19 16:56:04');
INSERT INTO `tb_user` VALUES ('6', 'lilei', '123456', '李磊', '23', '1', '1988-08-08', '2014-09-20 11:41:15', '2014-09-20 11:41:15');

2、搭建项目环境

• 创建一个普通的 maven 项目
• 导入maven依赖

        <!-- mysql驱动-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.47</version>
        </dependency>
        <!-- mybatis -->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.2</version>
        </dependency>
        <!-- 单元测试 -->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
        </dependency>

3、编写 mybatis-config.xml 核心配置文件

<?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：核心配置文件-->
<configuration>
    <!-- 设置启用数据库字段下划线映射到java对象的驼峰式命名属性，默认为false -->
    <settings>
        <setting name="mapUnderscoreToCamelCase" value="true"/>
    </settings>

    <!-- 配置数据库连接信息 -->
    <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://localhost:3306/mybatis?useSSL=true&amp;useUnicode=true&amp;characterEncoding=UTF-8"/>
                <property name="username" value="root"/>
                <property name="password" value="900415"/>
            </dataSource>
        </environment>
    </environments>
    <!-- 注册mapper文件到核心配置中 -->
    <mappers>
        <mapper resource="mapper/UserMapper.xml"/>
    </mappers>

</configuration>

4、编写mybatis工具类

public class MybatisUtil {
    private static SqlSessionFactory sqlSessionFactory;
    /* 初始化一次即可 */
    static {
        try {
            String resource = "mybatis-config.xml";
            InputStream inputStream = Resources.getResourceAsStream(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    // 提供获取 sqlSession 对象的方法
    public static SqlSession getSqlSession(){
        return sqlSessionFactory.openSession();
    }
}

5、编写代码

• 实体类（简写）

public class User {
    private int id;
    private String userName;
    private String password;
    private String name;
    private int age;
    private int sex;
    private Date birthday;
    private Date created;
    private Date updated;
}

• Dao 接口

public interface UserDao {
    List<User> queryUserList();
}

• 编写一个 mapper 配置文件来替换原来 dao 层的实现类与数据库交互

<?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：绑定一个对应的Dao接口-->
<mapper namespace="com.study.dao.UserDao">

    <!-- 查询语句 -->
    <select id="queryUserList" resultType="com.study.pojo.User">
        select * from tb_user
    </select>
</mapper>

• 测试

public class UserDaoTest {
    @Test
    public void Test01(){
        // 获取sqlSession对象
        SqlSession sqlSession = MybatisUtil.getSqlSession();
        // 方式一
        UserDao userDao = sqlSession.getMapper(UserDao.class);
        List<User> users = userDao.queryUserList();
        // 方式二
//        List<User> users = sqlSession.selectList("com.study.dao.UserDao.queryUserList");
        for (User user : users) {
            System.out.println(user);
        }
        sqlSession.close();
    }
}