Spring中Bean的加载与SpringBoot的初始化流程详解

目录

• 前言
• 第一章 Spring中Bean的一些简单概念

• 1.1 SpingIOC简介
• 1.2 BeanFactory

• 1.2.1 BeanDefinition
• 1.2.2 BeanDefinitionRegistry
• 1.2.3 BeanFactory结构图

• 2.1 准备阶段

• 2.2.1 监听器分析
• 2.2.2 refreshContext

public abstract class AbstractBeanDefinition extends BeanMetadataAttributeAccessor
        implements BeanDefinition, Cloneable {
    private volatile Object beanClass;
    private String scope = SCOPE_DEFAULT;
    private boolean abstractFlag = false;
    private boolean lazyInit = false;
    private int autowireMode = AUTOWIRE_NO;
    private int dependencyCheck = DEPENDENCY_CHECK_NONE;
    private String[] dependsOn;
    private ConstructorArgumentValues constructorArgumentValues;
    private MutablePropertyValues propertyValues;
    private String factoryBeanName;
    private String factoryMethodName;
    private String initMethodName;
    private String destroyMethodName;
}

private final Map<String, BeanDefinition> beanDefinitionMap = new ConcurrentHashMap<>(256);

@SpringBootApplication
public class RepApplication {
	public static void main(String[] args) {
        //要理解的SpringApplication
	SpringApplication.run(RepApplication.class, args);
	}
}

public static ConfigurableApplicationContext run(Class<?>[] primarySources,
			String[] args) {
		return new SpringApplication(primarySources).run(args);
	}

public SpringApplication(ResourceLoader resourceLoader, Class<?>... primarySources) {
		this.resourceLoader = resourceLoader;
		Assert.notNull(primarySources, "PrimarySources must not be null");
		this.primarySources = new LinkedHashSet<>(Arrays.asList(primarySources));
        //推断web应用类型
		this.webApplicationType = WebApplicationType.deduceFromClasspath();
        //加载应用上下文初始化器
		setInitializers((Collection) getSpringFactoriesInstances(
				ApplicationContextInitializer.class));
        //加载应用事件监听器
		setListeners((Collection) getSpringFactoriesInstances(ApplicationListener.class));
		this.mainApplicationClass = deduceMainApplicationClass();
	}

public ConfigurableApplicationContext run(String... args) {
		StopWatch stopWatch = new StopWatch();
		stopWatch.start();
		ConfigurableApplicationContext context = null;
		Collection<SpringBootExceptionReporter> exceptionReporters = new ArrayList<>();
		configureHeadlessProperty();
        //获得监听器
		SpringApplicationRunListeners listeners = getRunListeners(args);
        //运行监听器
		listeners.starting();
		try {
            //应用上下文
			ApplicationArguments applicationArguments = new DefaultApplicationArguments(
					args);
            //环境
			ConfigurableEnvironment environment = prepareEnvironment(listeners,
					applicationArguments);
			configureIgnoreBeanInfo(environment);
			Banner printedBanner = printBanner(environment);
            //依据不同的配置加载不同的ApplicationContext
			context = createApplicationContext();
			exceptionReporters = getSpringFactoriesInstances(
					SpringBootExceptionReporter.class,
					new Class[] { ConfigurableApplicationContext.class }, context);
			prepareContext(context, environment, listeners, applicationArguments,
					printedBanner);
			refreshContext(context);
			afterRefresh(context, applicationArguments);
			stopWatch.stop();
			if (this.logStartupInfo) {
				new StartupInfoLogger(this.mainApplicationClass)
						.logStarted(getApplicationLog(), stopWatch);
			}
			listeners.started(context);
			callRunners(context, applicationArguments);
		}
		catch (Throwable ex) {
			handleRunFailure(context, ex, exceptionReporters, listeners);
			throw new IllegalStateException(ex);
		}
		try {
			listeners.running(context);
		}
		catch (Throwable ex) {
			handleRunFailure(context, ex, exceptionReporters, null);
			throw new IllegalStateException(ex);
		}
		return context;
	}

//获得监听器
SpringApplicationRunListeners listeners = getRunListeners(args);
//运行监听器
listeners.starting();

class SpringApplicationRunListeners { 
	private final Log log; 
	private final List<SpringApplicationRunListener> listeners; 
	SpringApplicationRunListeners(Log log,
			Collection<? extends SpringApplicationRunListener> listeners) {
		this.log = log;
		this.listeners = new ArrayList<>(listeners);
	}
	public void starting() {
		for (SpringApplicationRunListener listener : this.listeners) {
			listener.starting();
		}
	}
	public void environmentPrepared(ConfigurableEnvironment environment) {
		for (SpringApplicationRunListener listener : this.listeners) {
			listener.environmentPrepared(environment);
		}
	}
	public void contextPrepared(ConfigurableApplicationContext context) {
		for (SpringApplicationRunListener listener : this.listeners) {
			listener.contextPrepared(context);
		}
	}
	public void contextLoaded(ConfigurableApplicationContext context) {
		for (SpringApplicationRunListener listener : this.listeners) {
			listener.contextLoaded(context);
		}
	}
	public void started(ConfigurableApplicationContext context) {
		for (SpringApplicationRunListener listener : this.listeners) {
			listener.started(context);
		}
	} 
	//省略... 
}

@Override
	public void environmentPrepared(ConfigurableEnvironment environment) {
		this.initialMulticaster.multicastEvent(new ApplicationEnvironmentPreparedEvent(
				this.application, this.args, environment));
	}

@Override
	public void multicastEvent(final ApplicationEvent event, @Nullable ResolvableType eventType) {
		ResolvableType type = (eventType != null ? eventType : resolveDefaultEventType(event));
		for (final ApplicationListener<?> listener : getApplicationListeners(event, type)) {
			Executor executor = getTaskExecutor();
			if (executor != null) {
				executor.execute(() -> invokeListener(listener, event));
			}
			else {
				invokeListener(listener, event);
			}
		}
	}

@Override
	public void refresh() throws BeansException, IllegalStateException {
		synchronized (this.startupShutdownMonitor) {
			// Prepare this context for refreshing.
			prepareRefresh();
			// Tell the subclass to refresh the internal bean factory.
			ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
			// Prepare the bean factory for use in this context.
			prepareBeanFactory(beanFactory);
			try {
				// 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();
			}
			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();
			}
		}
	}

private void refreshContext(ConfigurableApplicationContext context) {
		refresh(context);
		if (this.registerShutdownHook) {
			try {
				context.registerShutdownHook();
			}
			catch (AccessControlException ex) {
				// Not allowed in some environments.
			}
		}
	}

protected void afterRefresh(ConfigurableApplicationContext context,
			ApplicationArguments args) {
	}

refreshContext(context);

invokeBeanFactoryPostProcessors(beanFactory);