MyBatis是一款优秀的持久层构架,它支持定制化SQL语句、存储过程以及高级映射,可以通过简单的XML或注解配置和映射原生信息,将POJOs映射成数据库中的记录,从而方便进行增删改查的操作(官网)。本文会分别介绍通过XML、自动生成、注解三种传统使用MyBatis的方式以及在SpringBoot中使用MyBatis。
GitHub源码地址
1. XML配置方式使用MyBatis
1.1 引入依赖(jdbc,mysql,mybatis)
org.springframework.boot
spring-boot-starter-jdbc
org.mybatis.spring.boot
mybatis-spring-boot-starter
1.3.2
mysql
mysql-connector-java
runtime
1.2 配置数据库连接信息
resources:mybatis/mybatis.properties
jdbc.driver-class=com.mysql.jdbc.Driver
jdbc.user=root
jdbc.password=123456
jdbc.url=jdbc:mysql://localhost:3306/test
1.3 配置Mybatis
resources:mybatis/mybatis-config.xml
1.4 配置映射信息
resources:mybatis/mappers/UserMapper.xml
1.5运行测试
public class XmlConfigDemo {
public static void main(String[] args) throws IOException {
ResourceLoader resourceLoader = new DefaultResourceLoader();
Resource resource = resourceLoader.getResource("classpath:/mybatis/mybatis-config.xml");
InputStream inputStream = resource.getInputStream();
SqlSessionFactory sqlSessionFactory =
new SqlSessionFactoryBuilder().build(inputStream);
SqlSession session = sqlSessionFactory.openSession();
try {
User user = session.selectOne("com.hebaohua.springbootmybatis.mappers.UserMapper.selectUser", 4);
System.out.println(user);
} finally {
session.close();
}
}
}
运行效果:
2. 使用MyBatis配置生成器
此处只讲解在idea中使用maven连接Mysql的配置方式, 其它可以查看网址.
2.1 首先添加Maven插件
org.mybatis.generator
mybatis-generator-maven-plugin
1.3.5
mysql
mysql-connector-java
5.1.46
注意: 不要忘了下面的mysql驱动依赖
2.2 编写生成配置文件
注意命名为generatorConfig.xml,并且直接放在resources下面
2.3 执行生成命令
在项目根目录打开命令窗口并执行mvn mybatis-generator:generate
下图中的四个文件,然后其添加如XML方式中的配置信息。
2.4 运行测试
上一步中产生的文件提供了关于数据库user表中丰富的增删改查接口,使我们在使用起来非常的方便。
public class Demo {
public static void main(String[] args) throws IOException {
ResourceLoader resourceLoader = new DefaultResourceLoader();
Resource resource = resourceLoader.getResource("classpath:/mybatis/mybatis-config.xml");
InputStream inputStream = resource.getInputStream();
SqlSessionFactory sqlSessionFactory =
new SqlSessionFactoryBuilder().build(inputStream);
SqlSession session = sqlSessionFactory.openSession();
try {
UserMapper userMapper = session.getMapper(UserMapper.class);
List users = userMapper.selectByExample(null);
System.out.println(users);
} finally {
session.close();
}
}
}
运行效果:
3. 使用注解
注解的方式总是能减少繁琐的配置文件。
3.1 编写注解Mapper
@Mapper
public interface UserMapper {
@Results(value = {
@Result(property = "id", column = "id", id = true),
@Result(property = "name", column = "name"),
@Result(property = "age", column = "age")
})
@Select("SELECT id,name,age FROM user WHERE id = #{id}")
User selectUser(int id);
}
3.2 运行测试
同样需要引入全局配置文件,并注意要增加以下内容:
测试代码:
public class Demo {
public static void main(String[] args) throws IOException {
ResourceLoader resourceLoader = new DefaultResourceLoader();
Resource resource = resourceLoader.getResource("classpath:/mybatis/mybatis-config.xml");
InputStream inputStream = resource.getInputStream();
SqlSessionFactory sqlSessionFactory =
new SqlSessionFactoryBuilder().build(inputStream);
SqlSession session = sqlSessionFactory.openSession();
try {
UserMapper userMapper = session.getMapper(UserMapper.class);
User user= userMapper.selectUser(4);
System.out.println(user);
} finally {
session.close();
}
}
}
运行效果:
4.SpringBoot中使用MyBatis
通过查看 MybatisAutoConfiguration
以及MybatisProperties
源码可知,在SpringBoot的配置文件中配置好datasource以及以“mybatis”开头的相关配置就会自动装配SqlSessionFactory
,SqlSessionTemplate
对象,因此在Contorller中就可以直接使用。
@org.springframework.context.annotation.Configuration
@ConditionalOnClass({ SqlSessionFactory.class, SqlSessionFactoryBean.class })
@ConditionalOnBean(DataSource.class)
@EnableConfigurationProperties(MybatisProperties.class)
@AutoConfigureAfter(DataSourceAutoConfiguration.class)
public class MybatisAutoConfiguration
@ConfigurationProperties(prefix = MybatisProperties.MYBATIS_PREFIX)
public class MybatisProperties {
public static final String MYBATIS_PREFIX = "mybatis";
/**
* Location of MyBatis xml config file.
*/
private String configLocation;
SpringBoot配置文件:
spring.datasource.driver-class-name=com.mysql.jdbc.Driver
spring.datasource.username=root
spring.datasource.password=123456
spring.datasource.url=jdbc:mysql://localhost:3306/test
mybatis.config-location=classpath:/mybatis/mybatis-config.xml
Controller类:
@RestController
public class MyBatisController {
@Autowired
private SqlSessionTemplate sqlSessionTemplate;
@GetMapping("/user/{id}")
public User getUser(@PathVariable int id){
User user = sqlSessionTemplate.selectOne("com.hebaohua.springbootmybatisannotation.mappers.UserMapper.selectUser",id);
return user;
}
}
运行效果: