spring源码解读二 | 易学教程

上一篇文章说到了生命周期的初始化refresh方法

在refresh里面有如下方法，这里只讲关键的几个方法比如说invokeBeanFactoryPostProcessors和finishBeanFactoryInitialization

prepareRefresh();

// Tell the subclass to refresh the internal bean factory.
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();

// Prepare the bean factory for use in this context.
prepareBeanFactory(beanFactory);

// Allows post-processing of the bean factory in context subclasses.
postProcessBeanFactory(beanFactory);

// Invoke factory processors registered as beans in the context.
invokeBeanFactoryPostProcessors(beanFactory);

// Register bean processors that intercept bean creation.
registerBeanPostProcessors(beanFactory);

// Initialize message source for this context.
initMessageSource();

// Initialize event multicaster for this context.
initApplicationEventMulticaster();

// Initialize other special beans in specific context subclasses.
onRefresh();

// Check for listener beans and register them.
registerListeners();

// Instantiate all remaining (non-lazy-init) singletons.
finishBeanFactoryInitialization(beanFactory);

// Last step: publish corresponding event.
finishRefresh();

首先我们看这个invokeBeanFactoryPostProcessors方法的源码

/**
 * Instantiate and invoke all registered BeanFactoryPostProcessor beans,
 * respecting explicit order if given.
 * <p>Must be called before singleton instantiation.
 */
protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {
   PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory, getBeanFactoryPostProcessors());

   // Detect a LoadTimeWeaver and prepare for weaving, if found in the meantime
   // (e.g. through an @Bean method registered by ConfigurationClassPostProcessor)
   if (beanFactory.getTempClassLoader() == null && beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) {
      beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));
      beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
   }
}

继续跟invokeBeanFactoryPostProcessors源码，这里只贴出来关键的代码

String[] postProcessorNames =
      beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
for (String ppName : postProcessorNames) {
   if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
      currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
      processedBeans.add(ppName);
   }
}
sortPostProcessors(currentRegistryProcessors, beanFactory);
registryProcessors.addAll(currentRegistryProcessors);
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
currentRegistryProcessors.clear();

里面会执行beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);

这个方法，通过类型拿出类型为BeanDefinitionRegistryPostProcessor的处理器，在上一篇文章，通过

AnnotationConfigApplicationContext这个类的构造方法里面，完成了内置的一些类的添加，其中有一个叫

ConfigurationClassPostProcessor的类，也是在这个时候放到工厂容器里面的，我们看这个类源码

public class ConfigurationClassPostProcessor implements BeanDefinitionRegistryPostProcessor,
      PriorityOrdered, ResourceLoaderAware, BeanClassLoaderAware, EnvironmentAware {

很明显这个类实现了BeanDefinitionRegistryPostProcessor这个接口，所以通过beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);这个方法可以拿到这个类，然后放到currentRegistryProcessors 集合里面，接着执行invokeBeanDefinitionRegistryPostProcessors方法，点进去看这个方法源码

/**
 * Invoke the given BeanDefinitionRegistryPostProcessor beans.
 */
private static void invokeBeanDefinitionRegistryPostProcessors(
      Collection<? extends BeanDefinitionRegistryPostProcessor> postProcessors, BeanDefinitionRegistry registry) {

   for (BeanDefinitionRegistryPostProcessor postProcessor : postProcessors) {
      postProcessor.postProcessBeanDefinitionRegistry(registry);
   }
}

此时会执行ConfigurationClassPostProcessor的postProcessBeanDefinitionRegistry方法

/**
 * Derive further bean definitions from the configuration classes in the registry.
 */
@Override
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) {
   int registryId = System.identityHashCode(registry);
   if (this.registriesPostProcessed.contains(registryId)) {
      throw new IllegalStateException(
            "postProcessBeanDefinitionRegistry already called on this post-processor against " + registry);
   }
   if (this.factoriesPostProcessed.contains(registryId)) {
      throw new IllegalStateException(
            "postProcessBeanFactory already called on this post-processor against " + registry);
   }
   this.registriesPostProcessed.add(registryId);

   processConfigBeanDefinitions(registry);
}

继续跟进processConfigBeanDefinitions方法里面

Set<ConfigurationClass> alreadyParsed = new HashSet<>(configCandidates.size());
do {
   parser.parse(candidates);
   parser.validate();

   Set<ConfigurationClass> configClasses = new LinkedHashSet<>(parser.getConfigurationClasses());
   configClasses.removeAll(alreadyParsed);

   // Read the model and create bean definitions based on its content
   if (this.reader == null) {
      this.reader = new ConfigurationClassBeanDefinitionReader(
            registry, this.sourceExtractor, this.resourceLoader, this.environment,
            this.importBeanNameGenerator, parser.getImportRegistry());
   }

通过这个parse方法完成对工程里面添加了Controller，Service等注解，以及ImportSelectores，ImportBeanDefinitionRegistor的信息的解析处理，最后放到一个map里面存入这些解析完的BeanDefinition信息，后面Bean的实例化会用到这些信息，今天就先说到这里，下节课开始讲Bean实例化的生命周期过程

来源：CSDN

作者：溪枫小白

链接：https://blog.csdn.net/lj872224/article/details/104231284

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bean

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