mybatis源码分析(三) mybatis-spring整合源码分析

mybatis源码分析(三) mybatis-spring整合源码分析

一丶mybatis与springboot整合例子

　　项目例子代码地址

 

二丶springboot自动装配的关键配置代码

　　

　　org.mybatis.spring.boot.autoconfigure.MybatisAutoConfiguration

　　1) 实例化SqlSessionFactory, 注意的是, SqlSessionFactoryBean是一个工厂Bean, 最后调用SqlSessionFactoryBean#getObject()生成对应的SqlSessionFacatory

  @Bean
  @ConditionalOnMissingBean
  public SqlSessionFactory sqlSessionFactory(DataSource dataSource) throws Exception {
    SqlSessionFactoryBean factory = new SqlSessionFactoryBean();
    factory.setDataSource(dataSource);
    factory.setVfs(SpringBootVFS.class);
    if (StringUtils.hasText(this.properties.getConfigLocation())) {
      factory.setConfigLocation(this.resourceLoader.getResource(this.properties.getConfigLocation()));
    }
    applyConfiguration(factory);
    if (this.properties.getConfigurationProperties() != null) {
      factory.setConfigurationProperties(this.properties.getConfigurationProperties());
    }
    if (!ObjectUtils.isEmpty(this.interceptors)) {
      factory.setPlugins(this.interceptors);
    }
    if (this.databaseIdProvider != null) {
      factory.setDatabaseIdProvider(this.databaseIdProvider);
    }
    if (StringUtils.hasLength(this.properties.getTypeAliasesPackage())) {
      factory.setTypeAliasesPackage(this.properties.getTypeAliasesPackage());
    }
    if (this.properties.getTypeAliasesSuperType() != null) {
      factory.setTypeAliasesSuperType(this.properties.getTypeAliasesSuperType());
    }
    if (StringUtils.hasLength(this.properties.getTypeHandlersPackage())) {
      factory.setTypeHandlersPackage(this.properties.getTypeHandlersPackage());
    }
    if (!ObjectUtils.isEmpty(this.typeHandlers)) {
      factory.setTypeHandlers(this.typeHandlers);
    }
    if (!ObjectUtils.isEmpty(this.properties.resolveMapperLocations())) {
      factory.setMapperLocations(this.properties.resolveMapperLocations());
    }
    Set<String> factoryPropertyNames = Stream
        .of(new BeanWrapperImpl(SqlSessionFactoryBean.class).getPropertyDescriptors()).map(PropertyDescriptor::getName)
        .collect(Collectors.toSet());
    Class<? extends LanguageDriver> defaultLanguageDriver = this.properties.getDefaultScriptingLanguageDriver();
    if (factoryPropertyNames.contains("scriptingLanguageDrivers") && !ObjectUtils.isEmpty(this.languageDrivers)) {
      // Need to mybatis-spring 2.0.2+
      factory.setScriptingLanguageDrivers(this.languageDrivers);
      if (defaultLanguageDriver == null && this.languageDrivers.length == 1) {
        defaultLanguageDriver = this.languageDrivers[0].getClass();
      }
    }
    if (factoryPropertyNames.contains("defaultScriptingLanguageDriver")) {
      // Need to mybatis-spring 2.0.2+
      factory.setDefaultScriptingLanguageDriver(defaultLanguageDriver);
    }

    return factory.getObject();
  }

 　　2) 生成SqlSessionTemplate

@Bean
  @ConditionalOnMissingBean
  public SqlSessionTemplate sqlSessionTemplate(SqlSessionFactory sqlSessionFactory) {
    ExecutorType executorType = this.properties.getExecutorType();
    if (executorType != null) {
      return new SqlSessionTemplate(sqlSessionFactory, executorType);
    } else {
      return new SqlSessionTemplate(sqlSessionFactory);
    }
  }

 　　3)扫描Mapper类文件

 　　在配置@MapperScan注解之后,会调用MapperScannerRegistrar,会创建MapperScannerConfigurer bean定义及对象,然后根据MapperScan中的值,创建Mapper接口对应的MapperFactoryBean,在交由Spring管理的同时,可以生成对应的Mapper类,即使用SqlSession获取对应的Mapper对象.

/**
   * 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 {

    private BeanFactory beanFactory;

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

      if (!AutoConfigurationPackages.has(this.beanFactory)) {
        logger.debug("Could not determine auto-configuration package, automatic mapper scanning disabled.");
        return;
      }

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

      List<String> packages = AutoConfigurationPackages.get(this.beanFactory);
      if (logger.isDebugEnabled()) {
        packages.forEach(pkg -> 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())
          // Need to mybatis-spring 2.0.2+
          .filter(x -> x.getName().equals("lazyInitialization")).findAny()
          .ifPresent(x -> builder.addPropertyValue("lazyInitialization", "${mybatis.lazy-initialization:false}"));
      registry.registerBeanDefinition(MapperScannerConfigurer.class.getName(), builder.getBeanDefinition());
    }

    @Override
    public void setBeanFactory(BeanFactory beanFactory) {
      this.beanFactory = beanFactory;
    }

  }

 　　

　　

　　MapperScannerConfigurer#postProcessBeanDefinitionRegistry()

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

    ClassPathMapperScanner scanner = new ClassPathMapperScanner(registry);
    scanner.setAddToConfig(this.addToConfig);
    scanner.setAnnotationClass(this.annotationClass);
    scanner.setMarkerInterface(this.markerInterface);
    scanner.setSqlSessionFactory(this.sqlSessionFactory);
    scanner.setSqlSessionTemplate(this.sqlSessionTemplate);
    scanner.setSqlSessionFactoryBeanName(this.sqlSessionFactoryBeanName);
    scanner.setSqlSessionTemplateBeanName(this.sqlSessionTemplateBeanName);
    scanner.setResourceLoader(this.applicationContext);
    scanner.setBeanNameGenerator(this.nameGenerator);
    scanner.setMapperFactoryBeanClass(this.mapperFactoryBeanClass);
    if (StringUtils.hasText(lazyInitialization)) {
      scanner.setLazyInitialization(Boolean.valueOf(lazyInitialization));
    }
    scanner.registerFilters();
　　//委派给ClassPathMapperScanner#doScan()处理
    scanner.scan(
        StringUtils.tokenizeToStringArray(this.basePackage, ConfigurableApplicationContext.CONFIG_LOCATION_DELIMITERS));
  }

　　ClassPathMapperScanner#doScan()

/**
   * Calls the parent search that will search and register all the candidates. Then the registered objects are post
   * processed to set them as MapperFactoryBeans
   */
  @Override
  public Set<BeanDefinitionHolder> doScan(String... basePackages) {
    Set<BeanDefinitionHolder> beanDefinitions = super.doScan(basePackages);

    if (beanDefinitions.isEmpty()) {
      LOGGER.warn(() -> "No MyBatis mapper was found in '" + Arrays.toString(basePackages)
          + "' package. Please check your configuration.");
    } else {
      processBeanDefinitions(beanDefinitions);
    }

    return beanDefinitions;
  }

  private void processBeanDefinitions(Set<BeanDefinitionHolder> beanDefinitions) {
    GenericBeanDefinition definition;
    for (BeanDefinitionHolder holder : beanDefinitions) {
      definition = (GenericBeanDefinition) holder.getBeanDefinition();
      String beanClassName = definition.getBeanClassName();
      LOGGER.debug(() -> "Creating MapperFactoryBean with name '" + holder.getBeanName() + "' and '" + beanClassName
          + "' mapperInterface");

      // the mapper interface is the original class of the bean
      // but, the actual class of the bean is MapperFactoryBean
      definition.getConstructorArgumentValues().addGenericArgumentValue(beanClassName); // issue #59
      definition.setBeanClass(this.mapperFactoryBeanClass);

      definition.getPropertyValues().add("addToConfig", this.addToConfig);

      boolean explicitFactoryUsed = false;
      if (StringUtils.hasText(this.sqlSessionFactoryBeanName)) {
        definition.getPropertyValues().add("sqlSessionFactory",
            new RuntimeBeanReference(this.sqlSessionFactoryBeanName));
        explicitFactoryUsed = true;
      } else if (this.sqlSessionFactory != null) {
        definition.getPropertyValues().add("sqlSessionFactory", this.sqlSessionFactory);
        explicitFactoryUsed = true;
      }

      if (StringUtils.hasText(this.sqlSessionTemplateBeanName)) {
        if (explicitFactoryUsed) {
          LOGGER.warn(
              () -> "Cannot use both: sqlSessionTemplate and sqlSessionFactory together. sqlSessionFactory is ignored.");
        }
        definition.getPropertyValues().add("sqlSessionTemplate",
            new RuntimeBeanReference(this.sqlSessionTemplateBeanName));
        explicitFactoryUsed = true;
      } else if (this.sqlSessionTemplate != null) {
        if (explicitFactoryUsed) {
          LOGGER.warn(
              () -> "Cannot use both: sqlSessionTemplate and sqlSessionFactory together. sqlSessionFactory is ignored.");
        }
        definition.getPropertyValues().add("sqlSessionTemplate", this.sqlSessionTemplate);
        explicitFactoryUsed = true;
      }

      if (!explicitFactoryUsed) {
        LOGGER.debug(() -> "Enabling autowire by type for MapperFactoryBean with name '" + holder.getBeanName() + "'.");
        definition.setAutowireMode(AbstractBeanDefinition.AUTOWIRE_BY_TYPE);
      }
      definition.setLazyInit(lazyInitialization);
    }
  }

　　

 三丶思考

　　Mybatis和Spring的整合, 即是在符合Spring的规则下, 使用Mybatis.

　　如, 使用Mybatis的最主要的两个步骤, 一, 构建对应的SqlSessionFactory  二, 获取对应的Mapper对象. 这分别对应的MybatisAutoConfiguration的两个配置, sqlSessionFactory(DataSource dataSource), 和 AutoConfiguredMapperScannerRegistrar

　　方法sqlSessionFactory(DataSource dataSource)生成的sqlSessionFactory,该实体类交由Spring管理

　　使用@MapperScan指定了mapper接口之后, 触发调用AutoConfiguredMapperScannerRegistrar, 注册MapperScannerConfigurer Bean 定义之后, 委派ClassPathMapperScanner将扫描的mapper接口, 注册成MapperFactoryBean, 最后由MapperFactoryBean生成mapper对象.