SpringBoot 刷新上下文7--执行BeanFactoryPostProcessor

SpringBoot刷新上下文一共七篇，基于SpringBoot 2.2.7.RELEASE，Spring 5.2.6.RELEASE
SpringBoot 刷新上下文1–主流程
SpringBoot 刷新上下文2–执行BeanDefinitionRegistryPostProcessor
SpringBoot 刷新上下文3–解析引导类
SpringBoot 刷新上下文4–处理ComponentScan
SpringBoot 刷新上下文5–处理其他注解
SpringBoot 刷新上下文6–加载并注册BeanDefinition
SpringBoot 刷新上下文7–执行BeanFactoryPostProcessor

2.2、调用BeanFactoryPostProcessor

//org.springframework.context.support.PostProcessorRegistrationDelegate#invokeBeanFactoryPostProcessors(java.util.Collection, org.springframework.beans.factory.config.ConfigurableListableBeanFactory)
private static void invokeBeanFactoryPostProcessors(Collection<? extends BeanFactoryPostProcessor> postProcessors, ConfigurableListableBeanFactory beanFactory) {

    for (BeanFactoryPostProcessor postProcessor : postProcessors) {
        postProcessor.postProcessBeanFactory(beanFactory);
    }
}

2.2.1、ConfigurationClassPostProcessor

org.springframework.boot.autoconfigure.SharedMetadataReaderFactoryContextInitializer.CachingMetadataReaderFactoryPostProcessor 和 org.springframework.boot.context.ConfigurationWarningsApplicationContextInitializer.ConfigurationWarningsPostProcessor 的 postProcessBeanFactory 方法都是空实现。

//org.springframework.context.annotation.ConfigurationClassPostProcessor#postProcessBeanFactory
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) {
    //获取factoryId
    int factoryId = System.identityHashCode(beanFactory);
    // 已经处理过，报错
    if (this.factoriesPostProcessed.contains(factoryId)) {
        throw new IllegalStateException(
            "postProcessBeanFactory already called on this post-processor against " + beanFactory);
    }
    this.factoriesPostProcessed.add(factoryId);
    if (!this.registriesPostProcessed.contains(factoryId)) {
        // BeanDefinitionRegistryPostProcessor hook apparently not supported...
        // Simply call processConfigurationClasses lazily at this point then.
        // 如果该 factoryId 没有处理过，调用上面的处理方法进行处理
        processConfigBeanDefinitions((BeanDefinitionRegistry) beanFactory);
    }
	//增强配置类，代理
    enhanceConfigurationClasses(beanFactory);
    beanFactory.addBeanPostProcessor(new ImportAwareBeanPostProcessor(beanFactory));
}

//org.springframework.context.annotation.ConfigurationClassPostProcessor#enhanceConfigurationClasses
public void enhanceConfigurationClasses(ConfigurableListableBeanFactory beanFactory) {
    //被@Configuration标注且proxyBeanMethods是true的类集合
    Map<String, AbstractBeanDefinition> configBeanDefs = new LinkedHashMap<>();
    //获取ioc中注册的所有bean的名称，遍历
    for (String beanName : beanFactory.getBeanDefinitionNames()) {
        // 根据bean名称获取BeanDefinition
        BeanDefinition beanDef = beanFactory.getBeanDefinition(beanName);
        // 获取BeanDefinition的org.springframework.context.annotation.ConfigurationClassPostProcessor.configurationClass 属性
        Object configClassAttr = beanDef.getAttribute(ConfigurationClassUtils.CONFIGURATION_CLASS_ATTRIBUTE);
        MethodMetadata methodMetadata = null;
        // 被注解修饰类的BeanDefinition
        if (beanDef instanceof AnnotatedBeanDefinition) {
            // 获取注解元信息
            methodMetadata = ((AnnotatedBeanDefinition) beanDef).getFactoryMethodMetadata();
        }
        // 有configurationClass 属性 或者 被注解修饰
        if ((configClassAttr != null || methodMetadata != null) && beanDef instanceof AbstractBeanDefinition) {
            // Configuration class (full or lite) or a configuration-derived @Bean method
            // -> resolve bean class at this point...
            AbstractBeanDefinition abd = (AbstractBeanDefinition) beanDef;
            if (!abd.hasBeanClass()) {
                try {
                    abd.resolveBeanClass(this.beanClassLoader);
                }
                catch (Throwable ex) {
                    throw new IllegalStateException(
                        "Cannot load configuration class: " + beanDef.getBeanClassName(), ex);
                }
            }
        }
        // configurationClass 属性 是 full
        // 被 @Configuration 标注并且 proxyBeanMethods 是 true 的是 full，其他是 lite
        if (ConfigurationClassUtils.CONFIGURATION_CLASS_FULL.equals(configClassAttr)) {
            if (!(beanDef instanceof AbstractBeanDefinition)) {
                throw new BeanDefinitionStoreException("Cannot enhance @Configuration bean definition '" +
                                                       beanName + "' since it is not stored in an AbstractBeanDefinition subclass");
            }
            // log 级别 并且 单例bean已经创建过了，打个日志
            else if (logger.isInfoEnabled() && beanFactory.containsSingleton(beanName)) {
                logger.info("Cannot enhance @Configuration bean definition '" + beanName +
                            "' since its singleton instance has been created too early. The typical cause " +
                            "is a non-static @Bean method with a BeanDefinitionRegistryPostProcessor " +
                            "return type: Consider declaring such methods as 'static'.");
            }
            configBeanDefs.put(beanName, (AbstractBeanDefinition) beanDef);
        }
    }
    if (configBeanDefs.isEmpty()) {
        // nothing to enhance -> return immediately
        return;
    }
	//创建cglib代理类并且放入BeanDefinition中
    ConfigurationClassEnhancer enhancer = new ConfigurationClassEnhancer();
    for (Map.Entry<String, AbstractBeanDefinition> entry : configBeanDefs.entrySet()) {
        AbstractBeanDefinition beanDef = entry.getValue();
        // If a @Configuration class gets proxied, always proxy the target class
        beanDef.setAttribute(AutoProxyUtils.PRESERVE_TARGET_CLASS_ATTRIBUTE, Boolean.TRUE);
        // Set enhanced subclass of the user-specified bean class
        Class<?> configClass = beanDef.getBeanClass();
        Class<?> enhancedClass = enhancer.enhance(configClass, this.beanClassLoader);
        if (configClass != enhancedClass) {
            if (logger.isTraceEnabled()) {
                logger.trace(String.format("Replacing bean definition '%s' existing class '%s' with " +
                                           "enhanced class '%s'", entry.getKey(), configClass.getName(), enhancedClass.getName()));
            }
            beanDef.setBeanClass(enhancedClass);
        }
    }
}

这个方法对@Configration配置类做了一个 代理，用的Cglib

2.2.2、ConfigFileApplicationListener

//org.springframework.boot.context.config.ConfigFileApplicationListener.PropertySourceOrderingPostProcessor#postProcessBeanFactory
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
    reorderSources(this.context.getEnvironment());
}

//org.springframework.boot.context.config.ConfigFileApplicationListener.PropertySourceOrderingPostProcessor#reorderSources
private void reorderSources(ConfigurableEnvironment environment) {
    //DEFAULT_PROPERTIES = defaultProperties
    PropertySource<?> defaultProperties = environment.getPropertySources().remove(DEFAULT_PROPERTIES);
    if (defaultProperties != null) {
        environment.getPropertySources().addLast(defaultProperties);
    }
}

2.3、调用实现了优先级Order的BeanFactoryPostProcessor

//org.springframework.context.support.PropertySourcesPlaceholderConfigurer#postProcessBeanFactory
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
    if (this.propertySources == null) {
        this.propertySources = new MutablePropertySources();
        if (this.environment != null) {
            this.propertySources.addLast(
                new PropertySource<Environment>(ENVIRONMENT_PROPERTIES_PROPERTY_SOURCE_NAME, this.environment) {
                    @Override
                    @Nullable
                    public String getProperty(String key) {
                        return this.source.getProperty(key);
                    }
                }
            );
        }
        try {
            PropertySource<?> localPropertySource =
                new PropertiesPropertySource(LOCAL_PROPERTIES_PROPERTY_SOURCE_NAME, mergeProperties());
            if (this.localOverride) {
                this.propertySources.addFirst(localPropertySource);
            }
            else {
                this.propertySources.addLast(localPropertySource);
            }
        }
        catch (IOException ex) {
            throw new BeanInitializationException("Could not load properties", ex);
        }
    }

    processProperties(beanFactory, new PropertySourcesPropertyResolver(this.propertySources));
    this.appliedPropertySources = this.propertySources;
}

//org.springframework.context.support.PropertySourcesPlaceholderConfigurer#processProperties(org.springframework.beans.factory.config.ConfigurableListableBeanFactory, org.springframework.core.env.ConfigurablePropertyResolver)
protected void processProperties(ConfigurableListableBeanFactory beanFactoryToProcess, final ConfigurablePropertyResolver propertyResolver) throws BeansException {

    propertyResolver.setPlaceholderPrefix(this.placeholderPrefix);
    propertyResolver.setPlaceholderSuffix(this.placeholderSuffix);
    propertyResolver.setValueSeparator(this.valueSeparator);

    StringValueResolver valueResolver = strVal -> {
        String resolved = (this.ignoreUnresolvablePlaceholders ?
                           propertyResolver.resolvePlaceholders(strVal) :
                           propertyResolver.resolveRequiredPlaceholders(strVal));
        if (this.trimValues) {
            resolved = resolved.trim();
        }
        return (resolved.equals(this.nullValue) ? null : resolved);
    };

    doProcessProperties(beanFactoryToProcess, valueResolver);
}

//org.springframework.beans.factory.config.PlaceholderConfigurerSupport#doProcessProperties
protected void doProcessProperties(ConfigurableListableBeanFactory beanFactoryToProcess, StringValueResolver valueResolver) {

    BeanDefinitionVisitor visitor = new BeanDefinitionVisitor(valueResolver);

    String[] beanNames = beanFactoryToProcess.getBeanDefinitionNames();
    for (String curName : beanNames) {
        // Check that we're not parsing our own bean definition,
        // to avoid failing on unresolvable placeholders in properties file locations.
        if (!(curName.equals(this.beanName) && beanFactoryToProcess.equals(this.beanFactory))) {
            BeanDefinition bd = beanFactoryToProcess.getBeanDefinition(curName);
            try {
                visitor.visitBeanDefinition(bd);
            }
            catch (Exception ex) {
                throw new BeanDefinitionStoreException(bd.getResourceDescription(), curName, ex.getMessage(), ex);
            }
        }
    }

    // New in Spring 2.5: resolve placeholders in alias target names and aliases as well.
    beanFactoryToProcess.resolveAliases(valueResolver);

    // New in Spring 3.0: resolve placeholders in embedded values such as annotation attributes.
    beanFactoryToProcess.addEmbeddedValueResolver(valueResolver);
}

2.4、调用实现了普通Order的BeanFactoryPostProcessor

//org.springframework.boot.context.properties.ConfigurationPropertiesBeanDefinitionValidator#postProcessBeanFactory
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
    //对单例bean校验
    for (String beanName : beanFactory.getBeanDefinitionNames()) {
        if (!(beanFactory.containsSingleton(beanName) || isValueObjectBeanDefinition(beanFactory, beanName))) {
            validate(beanFactory, beanName);
        }
    }
}

2.5、调用没有实现order的BeanFactoryPostProcessor

2.5.1、EventListenerMethodProcessor

//org.springframework.context.event.EventListenerMethodProcessor#postProcessBeanFactory
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) {
    this.beanFactory = beanFactory;
	//将所有的EventListenerMethodProcessor 排序
    Map<String, EventListenerFactory> beans = beanFactory.getBeansOfType(EventListenerFactory.class, false, false);
    List<EventListenerFactory> factories = new ArrayList<>(beans.values());
    AnnotationAwareOrderComparator.sort(factories);
    this.eventListenerFactories = factories;
}

2.5.2、PreserveErrorControllerTargetClassPostProcessor

//org.springframework.boot.autoconfigure.web.servlet.error.ErrorMvcAutoConfiguration.PreserveErrorControllerTargetClassPostProcessor#postProcessBeanFactory
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
    //获取所有的errorController
    String[] errorControllerBeans = beanFactory.getBeanNamesForType(ErrorController.class, false, false);
    for (String errorControllerBean : errorControllerBeans) {
        try {
            //AutoProxyUtils.PRESERVE_TARGET_CLASS_ATTRIBUTE = org.springframework.aop.framework.autoproxy.AutoProxyUtils.preserveTargetClass
            // 将 preserveTargetClass 属性 设置为true
            beanFactory.getBeanDefinition(errorControllerBean)
                .setAttribute(AutoProxyUtils.PRESERVE_TARGET_CLASS_ATTRIBUTE, Boolean.TRUE);
        }
        catch (Throwable ex) {
            // Ignore
        }
    }
}