导入相关依赖

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"><modelVersion>4.0.0</modelVersion><groupId>com.minifull</groupId><artifactId>my_mybatis</artifactId><version>1.0-SNAPSHOT</version><packaging>jar</packaging><!-- 导入依赖 --><dependencies><!-- mybatis --><dependency><groupId>org.mybatis</groupId><artifactId>mybatis</artifactId><version>3.4.5</version></dependency><!-- 数据库驱动 --><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><version>5.1.8</version><scope>runtime</scope></dependency><!-- 日志 --><dependency><groupId>log4j</groupId><artifactId>log4j</artifactId><version>1.2.17</version></dependency><!-- JUnit --><dependency><groupId>junit</groupId><artifactId>junit</artifactId><version>4.11</version><scope>test</scope></dependency></dependencies>
</project>

创建数据库和表

-- 创建数据库
CREATE DATABASE IF NOT EXISTS db_mybatis CHARACTER SET utf8;
-- 创建数据表
DROP TABLE IF EXISTS `user`;
CREATE TABLE `user` (`id` int(11) NOT NULL auto_increment,`username` varchar(32) NOT NULL COMMENT '用户名称',`birthday` datetime default NULL COMMENT '生日',`sex` char(1) default NULL COMMENT '性别',`address` varchar(256) default NULL COMMENT '地址',PRIMARY KEY  (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
-- 添加记录
insert  into `user`(`id`,`username`,`birthday`,`sex`,`address`) values (41,'老王','2018-02-27 17:47:08','男','北京'),(42,'小二王','2018-03-02 15:09:37','女','北京金燕龙'),(43,'小二王','2018-03-04 11:34:34','女','北京金燕龙'),(45,'传智播客','2018-03-04 12:04:06','男','北京金燕龙'),(46,'老王','2018-03-07 17:37:26','男','北京'),(48,'小马宝莉','2018-03-08 11:44:00','女','北京修正');

创建实体类

@Data
public class User implements Serializable {private Integer id;private String username;private Date birthday;private String sex;private String address;
}

创建实体类的持久层接口

public interface UserMapper {/*** 查询所有用户** @return*/List<User> listAllUsers();
}

** 编写接口映射文件 **
UserMapper.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapperPUBLIC "-//mybatis.org//DTD Mapper 3.0//EN""http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.minifull.mapper.UserMapper"><!-- 配置查询所有用户 --><select id="listAllUsers" resultType="com.minifull.pojo.User">SELECT * FROM user</select>
</mapper>

**编写Mybatis的主配置文件 **
mybatis-config.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configurationPUBLIC "-//mybatis.org//DTD Config 3.0//EN""http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration><!-- 全局变量 --><properties><property name="driver" value="com.mysql.jdbc.Driver"/><property name="url" value="jdbc:mysql://localhost:3306/db_mybatis"/><property name="username" value="root"/><property name="password" value="root"/></properties><!--配置环境--><environments default="development"><environment id="development"><!-- 配置事务类型 --><transactionManager type="JDBC"></transactionManager><!-- 配置数据源（连接池） --><dataSource type="POOLED"><property name="driver" value="${driver}"/><property name="url" value="${url}"/><property name="username" value="${username}"/><property name="password" value="${password}"/></dataSource></environment></environments><!-- 指定映射文件 --><mappers><mapper resource="UserMapper.xml"/></mappers>
</configuration>

使用

public class MybatisTest {/*** Mybatis 入门案例*/@Testpublic void testInit() {try {// 1. 读取配置文件InputStream is = Resources.getResourceAsStream("mybatis-config.xml");// 2. 创建 SqlSessionFactory 工厂SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();SqlSessionFactory factory = builder.build(is);// 3. 从工厂获取 SqlSession 对象SqlSession sqlSession = factory.openSession();// 4. 使用 SqlSession 创建 dao接口的代理对象UserMapper mapper = sqlSession.getMapper(UserMapper.class);// 5. 使用代理对象执行查询List<User> users = mapper.listAllUsers();users.forEach(System.out::println);// 6. 释放资源sqlSession.close();is.close();} catch (IOException e) {e.printStackTrace();}}
}

注意事项

• mybatis的映射配置文件位置必须和dao接口的包结构相同
• 映射配置文件的 mapper 标签 namespace 属性的取值必须是 mapper 接口的全限定类名
• 映射配置文件的操作配置，id 属性的取值必须是 mapper 接口的方法名

做到以上几点，我们在开发中无需再写dao的实现类