MyBatis的原始使用

友情：原文链接：https://www.huaguoniang.top/archives/mybatisde-yuan-shi-shi-yong

背景

MyBatis作为java用户的主流ORM框架，在集成了Spring之后，大大提高了我们开发的效率。但是有没有想过，假如没有集成Spring，如何使用MyBatis呢？

本文将通过MyBatis的原始使用（没有依赖Spring，甚至没有IOC注入），来加深对MyBatis的原理理解。

原始使用

1. 依赖

<dependencies><!--mybatis依赖--><dependency><groupId>org.mybatis</groupId><artifactId>mybatis</artifactId><version>3.5.6</version></dependency><!--mysql驱动--><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><version>8.0.15</version></dependency><!--Junit依赖，用来执行单元测试--><dependency><groupId>junit</groupId><artifactId>junit</artifactId><version>4.10</version><scope>test</scope></dependency><!--lombok--><dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId><version>1.18.16</version></dependency></dependencies>

2. 数据库表

-- auto-generated definition
create table user
(id     int unsigned auto_increment comment 'ID'primary key,name   varchar(100)     null comment '姓名',age    tinyint unsigned null comment '年龄',gender tinyint unsigned null comment '性别, 1:男, 2:女',phone  varchar(11)      null comment '手机号'
)comment '用户表';

3. 实体类

@Data
@AllArgsConstructor
@NoArgsConstructor
public class User {private Integer id;private String name;private int age;private int gender;private String phone;}

4. Mapper接口类

public interface UserMapper {int insert(User user);
}

5. Mapper.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.qiang.dao.UserMapper"><insert id="insert">insert into User (id, name, age, gender, phone)value (#{id}, #{name}, #{age}, #{gender}, #{phone})</insert></mapper>

6. Service

public class UserServiceImpl {public String addUser(User user){if (user.getName().isEmpty()) {throw new RuntimeException("用户名不能为空");}return DaoUtils.execute(sqlSession -> {UserMapper mapper = sqlSession.getMapper(UserMapper.class);int count = mapper.insert(user);return count>0 ? "添加成功" : "添加失败";});}
}

7. 配置

jdbc.properties

driver=com.mysql.cj.jdbc.Driver
url=jdbc:mysql://localhost:3306/mybatis?useUnicode=true&characterEncoding=utf-8&useSSL=false&serverTimezone=Asia/Shanghai
username=root
password=1234

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><!--    加载resource资源包下的properties文件--><properties resource="jdbc.properties"/><settings><!--将表中字段的下划线自动转换为驼峰--><setting name="mapUnderscoreToCamelCase" value="true"/><!--开启延迟加载--><setting name="lazyLoadingEnabled" value="true"/></settings><!--    设置类型别名   将user /  User 自动映射为com.qiang.entity.User  在mapper.xml中不用写全类名 --><typeAliases><package name="com.qiang.entity"/></typeAliases><!--    配置连接数据库的环境--><environments default="development"><environment id="development"><transactionManager type="JDBC"/><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><!--    引入映射文件--><mappers><package name="com.qiang.dao"/></mappers>
</configuration>

8. DaoUtils

public class DaoUtils {private static SqlSessionFactory factory;static {String resource = "mybatis-config.xml";InputStream inputStream = null;try {inputStream = Resources.getResourceAsStream(resource);} catch (IOException e) {System.err.println("read mybatis-config.xml fail");e.printStackTrace();System.exit(1);}// 加载完mybatis-config.xml配置文件之后，会根据其中的配置信息创建SqlSessionFactory对象factory = new SqlSessionFactoryBuilder().build(inputStream);}public static <R> R execute(Function<SqlSession, R> function) {// 创建SqlSessionSqlSession session = factory.openSession();try {R apply = function.apply(session);// 提交事务session.commit();return apply;} catch (Throwable t) {// 异常，回滚事务session.rollback();System.out.println("execute error");throw t;} finally {// 关闭SqlSessionsession.close();}}
}

9. 测试

package com.qiang;import com.qiang.entity.User;
import com.qiang.service.UserServiceImpl;
import org.junit.Test;public class test {private UserServiceImpl userService;@Testpublic void test1(){userService = new UserServiceImpl();String result = userService.addUser(new User(1, "小王", 18, 1, "123456789"));System.out.println(result);}
}

SpringBootStarter使用

Spring Boot Starter集成

    <dependencies><!--mybatis依赖--><dependency><groupId>org.mybatis.spring.boot</groupId><artifactId>mybatis-spring-boot-starter</artifactId><version>2.1.1</version></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-test</artifactId><version>2.5.4</version><scope>test</scope></dependency><!--mysql驱动--><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><version>8.0.15</version></dependency><dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId><version>1.18.16</version></dependency></dependencies>

spring:data:datasource:driver-class-name: com.mysql.cj.jdbc.Driverurl: jdbc:mysql://localhost:3306/mybatis?serverTimezone=Asia/Shanghai&useUnicode=true&characterEncoding=utf-8username: rootpassword: 1234

@Service
public class UserServiceImpl {@Autowiredprivate UserMapper userMapper;public String addUser(User user){int count = userMapper.insert(user);return count>0 ? "添加成功" : "添加失败";}
}

@SpringBootTest
@ComponentScan(basePackages = "com.qiang")
public class test {@Autowiredprivate UserServiceImpl userService;@Testpublic void test1(){String result = userService.addUser(new User(3, "小王2", 18, 1, "123456789"));System.out.println(result);}
}

结语

原始使用的方式：

• 配置MyBatis-Config

• 使用Utils读取配置，创建sqlSession

• 执行的时候，要通过sqlSession获取对应的mapper

• 使用获取的mapper执行

Spring Boot + mybatis-spring-boot-starter的方式

• 自动创建 SqlSessionFactory（单例托管到 Spring 容器）

• 自动创建 SqlSession 并绑定到 当前线程（SqlSessionTemplate）

• 事务直接交给 Spring 的声明式事务 (@Transactional)，底层帮你 commit / rollback / close
  ---- 模板代码全没了，不需要 DaoUtils

---

我们要学的是MyBatis的框架原理，所以先从MyBatis的原始使用入手，学习一下基本的执行步骤，后续会慢慢深入到更加细节的内容中。