SpringBoot 整合 Mybatis

2023-04-01, by alamide

文档在这里

1.引入 mybatis-spring-boot-starter

这里 3.0 的版本，要求 jdk17 及以上，详见参考文档

<dependency>
    <groupId>org.mybatis.spring.boot</groupId>
    <artifactId>mybatis-spring-boot-starter</artifactId>
    <version>2.3.0</version>
</dependency>

2.基本使用

2.1 配置 application.yml

配置 DataSource ，及 *Mapper.xml 所在的目录

spring:
  datasource:
    driver-class-name: com.mysql.cj.jdbc.Driver
    username: root
    password: root
    url: jdbc:mysql://localhost:3306/guli_edu
mybatis:
  mapper-locations: classpath:mapper/*Mapper.xml

2.2 扫描 Mapper 接口

@Configuration
@MapperScan(basePackages = {"com.alamide.guli.mapper"})
public class MybatisConfig {
}

也可以不使用 @MapperScan ，而在 Mapper 接口上添加 @Mapper 注解

@Mapper
public interface EduTeacherMapper {
}

2.3 使用测试

@Slf4j
@SpringBootTest
class MainApplicationTest {
    @Autowired
    private EduTeacherMapper mapper;

    @Test
    public void testMybatis(){
        final List<EduTeacher> eduTeachers = mapper.selectByExample(null);
        log.info(eduTeachers.toString());
    }
}

2.4 Mybatis 配置

SpringBoot 中 Mybatis 的配置可以在 application.yml 中定义，也可以使用代码

配置文件

mybatis:
  mapper-locations: classpath:mapper/*Mapper.xml
  configuration:
    map-underscore-to-camel-case: true
    lazy-loading-enabled: true

代码配置

@Configuration
@MapperScan(basePackages = {"com.alamide.guli.mapper"})
public class MybatisConfig {
    @Bean
    ConfigurationCustomizer mybatisConfigurationCustomizer() {
        return new ConfigurationCustomizer() {
            @Override
            public void customize(org.apache.ibatis.session.Configuration configuration) {
                configuration.setMapUnderscoreToCamelCase(true);
                configuration.setCacheEnabled(true);
            }
        };
    }
}

3. 自动注册

MyBatis-Spring-Boot-Starter 会自动探测存在的 DataSource ，之后注册 SqlSessionTemplate

//MybatisAutoConfiguration.java
@Bean
@ConditionalOnMissingBean
public SqlSessionFactory sqlSessionFactory(DataSource dataSource) throws Exception {
    SqlSessionFactoryBean factory = new SqlSessionFactoryBean();
    factory.setDataSource(dataSource);
}

@Bean
@ConditionalOnMissingBean
public SqlSessionTemplate sqlSessionTemplate(SqlSessionFactory sqlSessionFactory) {
}

指定 MapperScan 的包

@SpringBootApplication
@MapperScan(basePackages = {"com.alamide.guli.mapper"})
public class MainApplication {
             
}

@Import(MapperScannerRegistrar.class)
@Repeatable(MapperScans.class)
public @interface MapperScan {}

最终一系列操作之后会来到这个类 ClassPathMapperScanner

public class ClassPathMapperScanner extends ClassPathBeanDefinitionScanner {
    
    private Class<? extends MapperFactoryBean> mapperFactoryBeanClass = MapperFactoryBean.class;

    private void processBeanDefinitions(Set<BeanDefinitionHolder> beanDefinitions) {
        definition.setBeanClass(this.mapperFactoryBeanClass);
    }
}

MapperFactoryBean 是 FactoryBean 的一个实现类

public class MapperFactoryBean<T> extends SqlSessionDaoSupport implements FactoryBean<T> {
    @Override
    public T getObject() throws Exception {
        return getSqlSession().getMapper(this.mapperInterface);
    }
}

所以我们只需要配置 DataSource 然后就可以直接获取 Mapper 了，其它的事 Mybatis 都替我们做了

Tags: Mybatis

~ belongs to alamide@163.com