SpringBoot 创建容器的实现

spring 容器的创建对应 SpringApplication 中 run 中调用的 createApplicationContext 方法。这里创建了一个 web 容器，接下就进去 prepareContext 容器准备阶段：

 private void prepareContext(ConfigurableApplicationContext context, ConfigurableEnvironment environment,
     SpringApplicationRunListeners listeners, ApplicationArguments applicationArguments, Banner printedBanner) {
   //为容器设置环境
   context.setEnvironment(environment);
   //这里的空实现留给开发者扩展，设置数据转换的ConversionService
   postProcessApplicationContext(context);
   //执行容器中的 Initializers 的 initialize 方法
   applyInitializers(context);
   listeners.contextPrepared(context);
   if (this.logStartupInfo) {
     logStartupInfo(context.getParent() == null);
     logStartupProfileInfo(context);
   }
   // Add boot specific singleton beans
   ConfigurableListableBeanFactory beanFactory = context.getBeanFactory();
   beanFactory.registerSingleton("springApplicationArguments", applicationArguments);
   if (printedBanner != null) {
     beanFactory.registerSingleton("springBootBanner", printedBanner);
   }
   if (beanFactory instanceof DefaultListableBeanFactory) {
     ((DefaultListableBeanFactory) beanFactory)
         .setAllowBeanDefinitionOverriding(this.allowBeanDefinitionOverriding);
   }
   if (this.lazyInitialization) {
     context.addBeanFactoryPostProcessor(new LazyInitializationBeanFactoryPostProcessor());
   }
   // Load the sources
   Set<Object> sources = getAllSources();
   Assert.notEmpty(sources, "Sources must not be empty");
   load(context, sources.toArray(new Object[0]));
   listeners.contextLoaded(context);
 }

看一下这里的 load 方法,这里主要把我们的启动类作为 Bean 注册到了 Spring 的容器中。

 protected void load(ApplicationContext context, Object[] sources) {
   if (logger.isDebugEnabled()) {
     logger.debug("Loading source " + StringUtils.arrayToCommaDelimitedString(sources));
   }
   BeanDefinitionLoader loader = createBeanDefinitionLoader(getBeanDefinitionRegistry(context), sources);
   if (this.beanNameGenerator != null) {
     loader.setBeanNameGenerator(this.beanNameGenerator);
   }
   if (this.resourceLoader != null) {
     loader.setResourceLoader(this.resourceLoader);
   }
   if (this.environment != null) {
     loader.setEnvironment(this.environment);
   }
   loader.load();
 }

 /**
  * Load the sources into the reader.
  * @return the number of loaded beans
  */
 int load() {
   int count = 0;
   for (Object source : this.sources) {
     count += load(source);
   }
   return count;
 }

private int load(Object source) {
   Assert.notNull(source, "Source must not be null");
   if (source instanceof Class<?>) {
     return load((Class<?>) source);
   }
   if (source instanceof Resource) {
     return load((Resource) source);
   }
   if (source instanceof Package) {
     return load((Package) source);
   }
   if (source instanceof CharSequence) {
     return load((CharSequence) source);
   }
   throw new IllegalArgumentException("Invalid source type " + source.getClass());
 }

private int load(Class<?> source) {
   if (isGroovyPresent() && GroovyBeanDefinitionSource.class.isAssignableFrom(source)) {
     // Any GroovyLoaders added in beans{} DSL can contribute beans here
     GroovyBeanDefinitionSource loader = BeanUtils.instantiateClass(source, GroovyBeanDefinitionSource.class);
     load(loader);
   }
   if (isEligible(source)) {
     this.annotatedReader.register(source);
     return 1;
   }
   return 0;
 }

再来看下 contextLoaded 方法，这里将上下文设置到 * 中，同时也把 * 添加到上下文中。最后发布了一个 ApplicationPreparedEvent 事件。

 public void contextLoaded(ConfigurableApplicationContext context) {
   for (ApplicationListener<?> listener : this.application.getListeners()) {
     if (listener instanceof ApplicationContextAware) {
       ((ApplicationContextAware) listener).setApplicationContext(context);
     }
     context.addApplicationListener(listener);
   }
   this.initialMulticaster.multicastEvent(new ApplicationPreparedEvent(this.application, this.args, context));
 }

来源：https://segmentfault.com/a/1190000037447793