深入理解Mybatis解析Mapper底层原理

2020-12-07 19:37:26.025  WARN 25756 --- [           main] o.m.s.mapper.ClassPathMapperScanner      : Skipping MapperFactoryBean with name 'roleMapper' and 'com.dunzung.java.spring.mapper.RoleMapper' mapperInterface. Bean already defined with the same name!

2020-12-07 19:37:26.025  WARN 25756 --- [           main] o.m.s.mapper.ClassPathMapperScanner      : Skipping MapperFactoryBean with name 'userMapper' and 'com.dunzung.java.spring.mapper.UserMapper' mapperInterface. Bean already defined with the same name!
2

@Configuration
@MapperScan(basePackages = "com.dunzung.**.mapper.**")
public class MybatisPlusConfiguration {
 @Bean
 public PaginationInterceptor paginationInterceptor() {
  PaginationInterceptor paginationInterceptor = new PaginationInterceptor();
  paginationInterceptor.setDbType(DbType.MYSQL);
  return paginationInterceptor;
 }
}

/**
* 自定义 Service 接口基类
*/
public interface MybatisService<T> extends IService<T> {
}

public interface RoleService extends MybatisService<RoleEntity> {
}

/**
* 自定义 Service 实现接口基类
*/
public class MybatisServiceImpl<M extends DaoMapper<T>, T> extends ServiceImpl<M, T> implements MybatisService<T> {
}

@Slf4j
@Service
public class RoleServiceImpl extends MybatisServiceImpl<RoleMapper, RoleEntity> implements RoleService {
}

@Mapper
public interface RoleMapper extends DaoMapper<RoleEntity> {
}

  /**
   * {@inheritDoc}
   */
  @Override
  protected boolean checkCandidate(String beanName, BeanDefinition beanDefinition) {
    if (super.checkCandidate(beanName, beanDefinition)) {
      return true;
    } else {
      LOGGER.warn(() -> "Skipping MapperFactoryBean with name '" + beanName + "' and '"
          + beanDefinition.getBeanClassName() + "' mapperInterface" + ". Bean already defined with the same name!");
      return false;
    }
  }
}

protected Set<BeanDefinitionHolder> doScan(String... basePackages) {
...
  for (String basePackage : basePackages) {
 Set<BeanDefinition> candidates = findCandidateComponents(basePackage);
 for (BeanDefinition candidate : candidates) {
  ...
  if (checkCandidate(beanName, candidate)) {
    ...
  }
 }
}

@Override
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) {
    if (this.processPropertyPlaceHolders) {
      processPropertyPlaceHolders();
    }

    ClassPathMapperScanner scanner = new ClassPathMapperScanner(registry);
    ...
    scanner.registerFilters();
    scanner.scan(
        StringUtils.tokenizeToStringArray(this.basePackage, ConfigurableApplicationContext.CONFIG_LOCATION_DELIMITERS));
}

/**
   * This will just scan the same base package as Spring Boot does. If you want
   * more power, you can explicitly use
   * {@link org.mybatis.spring.annotation.MapperScan} but this will get typed
   * mappers working correctly, out-of-the-box, similar to using Spring Data JPA
   * repositories.
   */
  public static class AutoConfiguredMapperScannerRegistrar
      implements BeanFactoryAware, ImportBeanDefinitionRegistrar, ResourceLoaderAware {

    private BeanFactory beanFactory;

    private ResourceLoader resourceLoader;

    @Override
    public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {

      logger.debug("Searching for mappers annotated with @Mapper");

      ClassPathMapperScanner scanner = new ClassPathMapperScanner(registry);

      try {
        if (this.resourceLoader != null) {
          scanner.setResourceLoader(this.resourceLoader);
        }

        List<String> packages = AutoConfigurationPackages.get(this.beanFactory);
        if (logger.isDebugEnabled()) {
          for (String pkg : packages) {
            logger.debug("Using auto-configuration base package '{}'", pkg);
          }
        }

        scanner.setAnnotationClass(Mapper.class);
        scanner.registerFilters();
        scanner.doScan(StringUtils.toStringArray(packages));
      } catch (IllegalStateException ex) {
        logger.debug("Could not determine auto-configuration package, automatic mapper scanning disabled.", ex);
      }
    } 
  }

  /**
   * {@link org.mybatis.spring.annotation.MapperScan} ultimately ends up
   * creating instances of {@link MapperFactoryBean}. If
   * {@link org.mybatis.spring.annotation.MapperScan} is used then this
   * auto-configuration is not needed. If it is _not_ used, however, then this
   * will bring in a bean registrar and automatically register components based
   * on the same component-scanning path as Spring Boot itself.
   */
  @org.springframework.context.annotation.Configuration
  @Import({ AutoConfiguredMapperScannerRegistrar.class })
  @ConditionalOnMissingBean(MapperFactoryBean.class)
  public static class MapperScannerRegistrarNotFoundConfiguration {

    @PostConstruct
    public void afterPropertiesSet() {
      logger.debug("No {} found.", MapperFactoryBean.class.getName());
    }
  }
}

@Configuration
@Import({MybatisAutoConfiguration.AutoConfiguredMapperScannerRegistrar.class})
@ConditionalOnMissingBean({MapperFactoryBean.class, MapperScannerConfigurer.class})
public static class MapperScannerRegistrarNotFoundConfiguration implements InitializingBean {
    public MapperScannerRegistrarNotFoundConfiguration() {
    }

  public void afterPropertiesSet() {
          MybatisAutoConfiguration.logger.debug("Not found configuration for registering mapper bean using @MapperScan, MapperFactoryBean and MapperScannerConfigurer.");
        }
    }

  public static class AutoConfiguredMapperScannerRegistrar implements BeanFactoryAware, ImportBeanDefinitionRegistrar {
        private BeanFactory beanFactory;

        public AutoConfiguredMapperScannerRegistrar() {
        }

        public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
            if (!AutoConfigurationPackages.has(this.beanFactory)) {
                MybatisAutoConfiguration.logger.debug("Could not determine auto-configuration package, automatic mapper scanning disabled.");
            } else {
                MybatisAutoConfiguration.logger.debug("Searching for mappers annotated with @Mapper");
                List<String> packages = AutoConfigurationPackages.get(this.beanFactory);
                if (MybatisAutoConfiguration.logger.isDebugEnabled()) {
                    packages.forEach((pkg) -> {
                        MybatisAutoConfiguration.logger.debug("Using auto-configuration base package '{}'", pkg);
                    });
                }
                BeanDefinitionBuilder builder = BeanDefinitionBuilder.genericBeanDefinition(MapperScannerConfigurer.class);
                builder.addPropertyValue("processPropertyPlaceHolders", true);
                builder.addPropertyValue("annotationClass", Mapper.class);
                builder.addPropertyValue("basePackage", StringUtils.collectionToCommaDelimitedString(packages));
                BeanWrapper beanWrapper = new BeanWrapperImpl(MapperScannerConfigurer.class);
                Stream.of(beanWrapper.getPropertyDescriptors()).filter((x) -> {
                    return x.getName().equals("lazyInitialization");
                }).findAny().ifPresent((x) -> {
                    builder.addPropertyValue("lazyInitialization", "${mybatis.lazy-initialization:false}");
                });
                registry.registerBeanDefinition(MapperScannerConfigurer.class.getName(), builder.getBeanDefinition());
            }
        }
        public void setBeanFactory(BeanFactory beanFactory) {
            this.beanFactory = beanFactory;
        }
    }
} 

<dependency>
    <groupId>org.mybatis</groupId>
    <artifactId>mybatis-spring</artifactId>
    <version>2.0.5</version>
    <scope>compile</scope>
</dependency>

<dependency>
    <groupId>org.mybatis</groupId>
    <artifactId>mybatis-spring</artifactId>
    <version>1.3.2</version> 
</dependency>