springboot mybatis 自動配置

先看自動配置類 MybatisAutoConfiguration 配置了幾個重要的bean

通過 SqlSessionFactoryBean 工廠bean配置SqlSessionFactory
SqlSessionTemplate
MapperScannerRegistrarNotFoundConfiguration 導入 AutoConfiguredMapperScannerRegistrar
AutoConfiguredMapperScannerRegistrar 注冊了 MapperScannerConfigurer bean定義

public class MybatisAutoConfiguration implements InitializingBean {

  private static final Logger logger = LoggerFactory.getLogger(MybatisAutoConfiguration.class);

  private final MybatisProperties properties;

  private final Interceptor[] interceptors;

  private final TypeHandler[] typeHandlers;

  private final LanguageDriver[] languageDrivers;

  private final ResourceLoader resourceLoader;

  private final DatabaseIdProvider databaseIdProvider;

  private final List<ConfigurationCustomizer> configurationCustomizers;

  、、、

// 配置 SqlSessionFactory   bean 
  @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();
  }

  private void applyConfiguration(SqlSessionFactoryBean factory) {
    Configuration configuration = this.properties.getConfiguration();
    if (configuration == null && !StringUtils.hasText(this.properties.getConfigLocation())) {
      configuration = new Configuration();
    }
    if (configuration != null && !CollectionUtils.isEmpty(this.configurationCustomizers)) {
      for (ConfigurationCustomizer customizer : this.configurationCustomizers) {
        customizer.customize(configuration);
      }
    }
    factory.setConfiguration(configuration);
  }

// 配置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);
    }
  }

  /**
   * 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.
   */
   // 注冊器注冊bean  MapperScannerConfigurer
  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;
    }

  }

  /**
   * If mapper registering configuration or mapper scanning configuration not present, this configuration allow to scan
   * mappers based on the same component-scanning path as Spring Boot itself.
   */
  @org.springframework.context.annotation.Configuration
  //  導入AutoConfiguredMapperScannerRegistrar  
  @Import(AutoConfiguredMapperScannerRegistrar.class)
  @ConditionalOnMissingBean({ MapperFactoryBean.class, MapperScannerConfigurer.class })
  public static class MapperScannerRegistrarNotFoundConfiguration implements InitializingBean {

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

  }

}

SqlSessionFactoryBean 工廠bean 建立SqlSessionFactory

public SqlSessionFactory getObject() throws Exception {
    if (this.sqlSessionFactory == null) {
      //  方法内建構SqlSessionFactory 
      afterPropertiesSet();
    }

    return this.sqlSessionFactory;
  }

public void afterPropertiesSet() throws Exception {
    notNull(dataSource, "Property 'dataSource' is required");
    notNull(sqlSessionFactoryBuilder, "Property 'sqlSessionFactoryBuilder' is required");
    state((configuration == null && configLocation == null) || !(configuration != null && configLocation != null),
        "Property 'configuration' and 'configLocation' can not specified with together");

    // 建構SqlSessionFactory 
    this.sqlSessionFactory = buildSqlSessionFactory();
  }



protected SqlSessionFactory buildSqlSessionFactory() throws Exception {

   
      
    if (this.mapperLocations != null) {
      if (this.mapperLocations.length == 0) {
        LOGGER.warn(() -> "Property 'mapperLocations' was specified but matching resources are not found.");
      } else {
      //  周遊mapper位址，及解析mapper xml檔案
        for (Resource mapperLocation : this.mapperLocations) {
          if (mapperLocation == null) {
            continue;
          }
          try {
            XMLMapperBuilder xmlMapperBuilder = new XMLMapperBuilder(mapperLocation.getInputStream(),
                targetConfiguration, mapperLocation.toString(), targetConfiguration.getSqlFragments());
             // 解析mapper xml 檔案，将解析的xml檔案内容方放到  targetConfiguration中 
            xmlMapperBuilder.parse();
          } catch (Exception e) {
            throw new NestedIOException("Failed to parse mapping resource: '" + mapperLocation + "'", e);
          } finally {
            ErrorContext.instance().reset();
          }
          LOGGER.debug(() -> "Parsed mapper file: '" + mapperLocation + "'");
        }
      }
    } else {
      LOGGER.debug(() -> "Property 'mapperLocations' was not specified.");
    }

    return this.sqlSessionFactoryBuilder.build(targetConfiguration);
  }

MapperScannerConfigurer 實作了 BeanDefinitionRegistryPostProcessor 接口的 postProcessBeanDefinitionRegistry 方法

public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) {
    if (this.processPropertyPlaceHolders) {
      processPropertyPlaceHolders();
    }
    //  掃描器掃描mapper 接口
    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);
    //this.mapperFactoryBeanClass為null時， 預設指派MapperFactoryBean
    scanner.setMapperFactoryBeanClass(this.mapperFactoryBeanClass);
    if (StringUtils.hasText(lazyInitialization)) {
      scanner.setLazyInitialization(Boolean.valueOf(lazyInitialization));
    }
    scanner.registerFilters();
    //  掃描包下的mapper接口
    scanner.scan(
        StringUtils.tokenizeToStringArray(this.basePackage, ConfigurableApplicationContext.CONFIG_LOCATION_DELIMITERS));
  }

ClassPathMapperScanner

掃描mapper接口

public Set<BeanDefinitionHolder> doScan(String... basePackages) {
    // 調用ClassPathMapperScanner的父類ClassPathBeanDefinitionScanner  掃描bean定義
    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 {
      // 對bean定義進行修改
      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
      //  設定beanclass 為org.mybatis.spring.mapper.MapperFactoryBean 
      // 是以所有mapper接口的beanclass都為MapperFactoryBean
      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);
    }
  }

  /**
   * {@inheritDoc}
   */
  @Override
  protected boolean isCandidateComponent(AnnotatedBeanDefinition beanDefinition) {
    return beanDefinition.getMetadata().isInterface() && beanDefinition.getMetadata().isIndependent();
  }

這裡總結下兩個重要配置

SqlSessionFactoryBean 在建立SqlSessionFactory 的時候，解析了xml 配置，并将解析結果放到了configuration中
MapperScannerConfigurer 建立 ClassPathMapperScanner 掃描mapper接口，修改mapper接口的beanclass 為 MapperFactoryBean.class 關于 MapperFactoryBean 是怎麼生成代理的看我的部落格

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