Spring5

一切从这段代码说起

public ClassPathXmlApplicationContext(String configLocation) throws BeansException {
		this(new String[] {configLocation}, true, null);
	}

实际上调用

public ClassPathXmlApplicationContext(
	String[] configLocations, boolean refresh, @Nullable ApplicationContext parent)
			throws BeansException {
		//1.调用父类容器构造方法，为容器设置好Bean资源加载器
		super(parent);
		//2.设置Bean配置信息的定位路径
		setConfigLocations(configLocations);
		if (refresh) {
		//3.开始对Bean配置资源载入
			refresh();
		}
	}

1.super（parent）

调用父类容器构造方法，为容器设置好Bean资源加载器

public AbstractApplicationContext(@Nullable ApplicationContext parent) {
		this();
		setParent(parent);
	}

看看this()

public AbstractApplicationContext() {
		this.resourcePatternResolver = getResourcePatternResolver();
	}

往里走

protected ResourcePatternResolver getResourcePatternResolver() {
		return new PathMatchingResourcePatternResolver(this);
	}

调用PathMatchingResourcePatternResolver的构造方法创建Spring资源加载器

public PathMatchingResourcePatternResolver(ResourceLoader resourceLoader) {
		Assert.notNull(resourceLoader, "ResourceLoader must not be null");
		this.resourceLoader = resourceLoader;
	}

看看setParent（parent）

public void setParent(@Nullable ApplicationContext parent) {
		this.parent = parent;
		if (parent != null) {
			Environment parentEnvironment = parent.getEnvironment();
			if (parentEnvironment instanceof ConfigurableEnvironment) {
				getEnvironment().merge((ConfigurableEnvironment) parentEnvironment);
			}
		}
	}

内部的getEnvironment（）
大概是创建一个所需的配置环境

public ConfigurableEnvironment getEnvironment() {
		if (this.environment == null) {
			this.environment = createEnvironment();
		}
		return this.environment;
	}

2. setConfigLocations(configLocations)

设置Bean配置信息的定位路径

public void setConfigLocation(String location) {
		setConfigLocations(StringUtils.tokenizeToStringArray(location, CONFIG_LOCATION_DELIMITERS));
	}
	public void setConfigLocations(@Nullable String... locations) {
		if (locations != null) {
			Assert.noNullElements(locations, "Config locations must not be null");
			this.configLocations = new String[locations.length];
			for (int i = 0; i < locations.length; i++) {
				this.configLocations[i] = resolvePath(locations[i]).trim();
			}
		}
		else {
			this.configLocations = null;
		}
	}

可见有setConfigLocation和setConfigLocations，也就是说，配置文件可以传一个或者多个

3.refresh()

载入Bean配置资源

public void refresh() throws BeansException, IllegalStateException {
		synchronized (this.startupShutdownMonitor) {
			//1. Prepare this context for refreshing.
			prepareRefresh();

			// 2.Tell the subclass to refresh the internal bean factory.
			ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();

			// 3.Prepare the bean factory for use in this context.
			prepareBeanFactory(beanFactory);

			try {
				//4. Allows post-processing of the bean factory in context subclasses.
				postProcessBeanFactory(beanFactory);

				// 5.Invoke factory processors registered as beans in the context.
				invokeBeanFactoryPostProcessors(beanFactory);

				// 6.Register bean processors that intercept bean creation.
				registerBeanPostProcessors(beanFactory);

				// 7.Initialize message source for this context.
				initMessageSource();

				// 8.Initialize event multicaster for this context.
				initApplicationEventMulticaster();

				// 9.Initialize other special beans in specific context subclasses.
				onRefresh();

				// 10.Check for listener beans and register them.
				registerListeners();

				// 11.Instantiate all remaining (non-lazy-init) singletons.
				finishBeanFactoryInitialization(beanFactory);

				// 12.Last step: publish corresponding event.
				finishRefresh();
			}

			catch (BeansException ex) {
				if (logger.isWarnEnabled()) {
					logger.warn("Exception encountered during context initialization - " +
							"cancelling refresh attempt: " + ex);
				}

				// Destroy already created singletons to avoid dangling resources.
				destroyBeans();

				// Reset 'active' flag.
				cancelRefresh(ex);

				// Propagate exception to caller.
				throw ex;
			}

			finally {
				// Reset common introspection caches in Spring's core, since we
				// might not ever need metadata for singleton beans anymore...
				resetCommonCaches();
			}
		}
	}

3.1 prepareRefresh()

为刷新准备上下文（材料）

protected void prepareRefresh() {
		this.startupDate = System.currentTimeMillis();
		this.closed.set(false);
		this.active.set(true);
		if (logger.isInfoEnabled()) {
			logger.info("Refreshing " + this);
		}
		// Initialize any placeholder property sources in the context environment
		// 初始化环境资源
		initPropertySources();
		// 验证参数合法性
		getEnvironment().validateRequiredProperties();
		this.earlyApplicationEvents = new LinkedHashSet<>();
	}

initPropertySources()其实是调用 initPropertySources(this.servletContext, this.servletConfig);

3.2 obtainFreshBeanFactory()

完成Spring IoC初始化过程：资源定位，将xml文件转为IO流载入，解析XML文件，封装成BeanDefinitionHold对象（此时，Bean并没有注册），然后再向Spring IoC容器注册解析的Bean（并没有完后才能依赖注入）
https://blog.csdn.net/qq_38526245/article/details/107244209

3.2.2 获取BeanFactory

public final ConfigurableListableBeanFactory getBeanFactory() {
		synchronized (this.beanFactoryMonitor) {
			if (this.beanFactory == null) {
				throw new IllegalStateException("BeanFactory not initialized or already closed - " +
						"call 'refresh' before accessing beans via the ApplicationContext");
			}
			return this.beanFactory;
		}
	}