spring源码解析③-BeanDefinitionRegistryPostProcessor和BeanFactoryPostProcessor以及BeanPostProcessor

BeanDefinitionRegistryPostProcessor和BeanFactoryPostProcessor

一句话描述：手动完成BeanDefinition的注册

接口定义：

public interface BeanDefinitionRegistryPostProcessor extends BeanFactoryPostProcessor {

    /**
     * Modify the application context's internal bean definition registry after its
     * standard initialization. All regular bean definitions will have been loaded,
     * but no beans will have been instantiated yet. This allows for adding further
     * bean definitions before the next post-processing phase kicks in.
     * @param registry the bean definition registry used by the application context
     * @throws org.springframework.beans.BeansException in case of errors
　　　　
     */
    void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException;

}

@FunctionalInterface
public interface BeanFactoryPostProcessor {

    /**
     * Modify the application context's internal bean factory after its standard
     * initialization. All bean definitions will have been loaded, but no beans
     * will have been instantiated yet. This allows for overriding or adding
     * properties even to eager-initializing beans.
     * @param beanFactory the bean factory used by the application context
     * @throws org.springframework.beans.BeansException in case of errors
     */
    void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException;

}

这里的实现可以了解下mybatis和spring整合

public class MapperScannerConfigurer implements BeanDefinitionRegistryPostProcessor, InitializingBean, ApplicationContextAware, BeanNameAware {

  private String basePackage;//用于指定要扫描的包

  private boolean addToConfig = true;

  private SqlSessionFactory sqlSessionFactory;

  private SqlSessionTemplate sqlSessionTemplate;

  private String sqlSessionFactoryBeanName;

  private String sqlSessionTemplateBeanName;

  private Class<? extends Annotation> annotationClass;//mapper接口上有指定的annotation才会被扫描

  private Class<?> markerInterface;//mapper接口继承与指定的接口才会被扫描

  private ApplicationContext applicationContext;//容器上下文

  private String beanName;

  private boolean processPropertyPlaceHolders;

  private BeanNameGenerator nameGenerator;

  /**
   * This property lets you set the base package for your mapper interface files.
   * <p>
   * You can set more than one package by using a semicolon or comma as a separator.
   * <p>
   * Mappers will be searched for recursively starting in the specified package(s).
   *
   * @param basePackage base package name
   */
  public void setBasePackage(String basePackage) {
    this.basePackage = basePackage;
  }

  /**
   * Same as {@code MapperFactoryBean#setAddToConfig(boolean)}.
   *
   * @param addToConfig
   * @see MapperFactoryBean#setAddToConfig(boolean)
   */
  public void setAddToConfig(boolean addToConfig) {
    this.addToConfig = addToConfig;
  }

  /**
   * This property specifies the annotation that the scanner will search for.
   * <p>
   * The scanner will register all interfaces in the base package that also have the
   * specified annotation.
   * <p>
   * Note this can be combined with markerInterface.
   *
   * @param annotationClass annotation class
   */
  public void setAnnotationClass(Class<? extends Annotation> annotationClass) {
    this.annotationClass = annotationClass;
  }

  /**
   * This property specifies the parent that the scanner will search for.
   * <p>
   * The scanner will register all interfaces in the base package that also have the
   * specified interface class as a parent.
   * <p>
   * Note this can be combined with annotationClass.
   *
   * @param superClass parent class
   */
  public void setMarkerInterface(Class<?> superClass) {
    this.markerInterface = superClass;
  }

  /**
   * Specifies which {@code SqlSessionTemplate} to use in the case that there is
   * more than one in the spring context. Usually this is only needed when you
   * have more than one datasource.
   * <p>
   * @deprecated Use {@link #setSqlSessionTemplateBeanName(String)} instead
   *
   * @param sqlSessionTemplate
   */
  @Deprecated
  public void setSqlSessionTemplate(SqlSessionTemplate sqlSessionTemplate) {
    this.sqlSessionTemplate = sqlSessionTemplate;
  }

  /**
   * Specifies which {@code SqlSessionTemplate} to use in the case that there is
   * more than one in the spring context. Usually this is only needed when you
   * have more than one datasource.
   * <p>
   * Note bean names are used, not bean references. This is because the scanner
   * loads early during the start process and it is too early to build mybatis
   * object instances.
   *
   * @since 1.1.0
   *
   * @param sqlSessionTemplateName Bean name of the {@code SqlSessionTemplate}
   */
  public void setSqlSessionTemplateBeanName(String sqlSessionTemplateName) {
    this.sqlSessionTemplateBeanName = sqlSessionTemplateName;
  }

  /**
   * Specifies which {@code SqlSessionFactory} to use in the case that there is
   * more than one in the spring context. Usually this is only needed when you
   * have more than one datasource.
   * <p>
   * @deprecated Use {@link #setSqlSessionFactoryBeanName(String)} instead.
   *
   * @param sqlSessionFactory
   */
  @Deprecated
  public void setSqlSessionFactory(SqlSessionFactory sqlSessionFactory) {
    this.sqlSessionFactory = sqlSessionFactory;
  }

  /**
   * Specifies which {@code SqlSessionFactory} to use in the case that there is
   * more than one in the spring context. Usually this is only needed when you
   * have more than one datasource.
   * <p>
   * Note bean names are used, not bean references. This is because the scanner
   * loads early during the start process and it is too early to build mybatis
   * object instances.
   *
   * @since 1.1.0
   *
   * @param sqlSessionFactoryName Bean name of the {@code SqlSessionFactory}
   */
  public void setSqlSessionFactoryBeanName(String sqlSessionFactoryName) {
    this.sqlSessionFactoryBeanName = sqlSessionFactoryName;
  }

  /**
   *
   * @since 1.1.1
   *
   * @param processPropertyPlaceHolders
   */
  public void setProcessPropertyPlaceHolders(boolean processPropertyPlaceHolders) {
    this.processPropertyPlaceHolders = processPropertyPlaceHolders;
  }

  /**
   * {@inheritDoc}
   */
  @Override
  public void setApplicationContext(ApplicationContext applicationContext) {
    this.applicationContext = applicationContext;
  }

  /**
   * {@inheritDoc}
   */
  @Override
  public void setBeanName(String name) {
    this.beanName = name;
  }

  /**
   * Gets beanNameGenerator to be used while running the scanner.
   *
   * @return the beanNameGenerator BeanNameGenerator that has been configured
   * @since 1.2.0
   */
  public BeanNameGenerator getNameGenerator() {
    return nameGenerator;
  }

  /**
   * Sets beanNameGenerator to be used while running the scanner.
   *
   * @param nameGenerator the beanNameGenerator to set
   * @since 1.2.0
   */
  public void setNameGenerator(BeanNameGenerator nameGenerator) {
    this.nameGenerator = nameGenerator;
  }

  /**
   * {@inheritDoc}
   */
  @Override
  public void afterPropertiesSet() throws Exception {
    notNull(this.basePackage, "Property 'basePackage' is required");
  }

  /**
   * {@inheritDoc}
   */
  @Override
  public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) {
    // left intentionally blank
  }

  /**
   * {@inheritDoc}
   * 下面代码spring 注入mapper接口的扫描
   * @since 1.0.2
   */
  @Override
  public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) {
    if (this.processPropertyPlaceHolders) {//占位符处理
      processPropertyPlaceHolders();
    }
    //实例化ClassPathMapperScanner，并对scanner相关属性进行配置
    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.registerFilters();//根据上述配置，生成过滤器，只扫描合条件的class
    //扫描指定的包以及其子包
    scanner.scan(StringUtils.tokenizeToStringArray(this.basePackage, ConfigurableApplicationContext.CONFIG_LOCATION_DELIMITERS));
  }

  /*
   * BeanDefinitionRegistries are called early in application startup, before
   * BeanFactoryPostProcessors. This means that PropertyResourceConfigurers will not have been
   * loaded and any property substitution of this class' properties will fail. To avoid this, find
   * any PropertyResourceConfigurers defined in the context and run them on this class' bean
   * definition. Then update the values.
   */
  private void processPropertyPlaceHolders() {
    Map<String, PropertyResourceConfigurer> prcs = applicationContext.getBeansOfType(PropertyResourceConfigurer.class);

    if (!prcs.isEmpty() && applicationContext instanceof ConfigurableApplicationContext) {
      BeanDefinition mapperScannerBean = ((ConfigurableApplicationContext) applicationContext)
          .getBeanFactory().getBeanDefinition(beanName);

      // PropertyResourceConfigurer does not expose any methods to explicitly perform
      // property placeholder substitution. Instead, create a BeanFactory that just
      // contains this mapper scanner and post process the factory.
      DefaultListableBeanFactory factory = new DefaultListableBeanFactory();
      factory.registerBeanDefinition(beanName, mapperScannerBean);

      for (PropertyResourceConfigurer prc : prcs.values()) {
        prc.postProcessBeanFactory(factory);
      }

      PropertyValues values = mapperScannerBean.getPropertyValues();

      this.basePackage = updatePropertyValue("basePackage", values);
      this.sqlSessionFactoryBeanName = updatePropertyValue("sqlSessionFactoryBeanName", values);
      this.sqlSessionTemplateBeanName = updatePropertyValue("sqlSessionTemplateBeanName", values);
    }
  }

  private String updatePropertyValue(String propertyName, PropertyValues values) {
    PropertyValue property = values.getPropertyValue(propertyName);

    if (property == null) {
      return null;
    }

    Object value = property.getValue();

    if (value == null) {
      return null;
    } else if (value instanceof String) {
      return value.toString();
    } else if (value instanceof TypedStringValue) {
      return ((TypedStringValue) value).getValue();
    } else {
      return null;
    }
  }

}

ClassPathMapperScanner 收集@Mapper注解

  @Override
  public Set<BeanDefinitionHolder> doScan(String... basePackages) {
	//通过父类的扫描，获取所有复合条件的BeanDefinitionHolder对象
    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 {
      //处理扫描得到的BeanDefinitionHolder集合，将集合中的每一个mapper接口转换成MapperFactoryBean后，注册至spring容器
      processBeanDefinitions(beanDefinitions);
    }

    return beanDefinitions;
  }