SpringSecurity6从入门到上天系列第七篇：讲明白SpringBoot的自动装配完善上篇文章中的结论

悠悠 2024-02-18 11:20 11阅读 0赞

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**文章目录**

一：SpringBoot的自动装配

1：从run方法到入口类内容被注册到注解解读器中。

2：解析入口类注解到加载Bean实例

--------------------

## 一：SpringBoot的自动装配 ##

### 1：从run方法到入口类内容被注册到注解解读器中。 ###

public static void main(String[] args) {
            SpringApplication.run(AlibabaApplication.class, args);
        }

然后走到了一个run方法：

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

查看这里边的构造器方法：

public SpringApplication(Class<?>... primarySources) {
    		this(null, primarySources);
    	}
    
    	public SpringApplication(ResourceLoader resourceLoader, Class<?>... primarySources) {
    		this.resourceLoader = resourceLoader;
    		Assert.notNull(primarySources, "PrimarySources must not be null");
    		this.primarySources = new LinkedHashSet<>(Arrays.asList(primarySources));
    		this.webApplicationType = WebApplicationType.deduceFromClasspath();
    		this.bootstrapRegistryInitializers = new ArrayList<>(
    				getSpringFactoriesInstances(BootstrapRegistryInitializer.class));
    		setInitializers((Collection) getSpringFactoriesInstances(ApplicationContextInitializer.class));
    		setListeners((Collection) getSpringFactoriesInstances(ApplicationListener.class));
    		this.mainApplicationClass = deduceMainApplicationClass();
    	}

随后，我们查看具体的run方法：

public ConfigurableApplicationContext run(String... args) {
    		long startTime = System.nanoTime();
    		DefaultBootstrapContext bootstrapContext = createBootstrapContext();
    		ConfigurableApplicationContext context = null;
    		configureHeadlessProperty();
    		SpringApplicationRunListeners listeners = getRunListeners(args);
    		listeners.starting(bootstrapContext, this.mainApplicationClass);
    		try {
    			ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);
    			ConfigurableEnvironment environment = prepareEnvironment(listeners, bootstrapContext, applicationArguments);
    			Banner printedBanner = printBanner(environment);
    			context = createApplicationContext();
    			context.setApplicationStartup(this.applicationStartup);
                //准备解析工作
    			prepareContext(bootstrapContext, context, environment, listeners, applicationArguments, printedBanner);
                //真正的解析工作
    			refreshContext(context);
    			afterRefresh(context, applicationArguments);
    			Duration timeTakenToStartup = Duration.ofNanos(System.nanoTime() - startTime);
    			if (this.logStartupInfo) {
    				new StartupInfoLogger(this.mainApplicationClass).logStarted(getApplicationLog(), timeTakenToStartup);
    			}
    			listeners.started(context, timeTakenToStartup);
    			callRunners(context, applicationArguments);
    		}
    		catch (Throwable ex) {
    			if (ex instanceof AbandonedRunException) {
    				throw ex;
    			}
    			handleRunFailure(context, ex, listeners);
    			throw new IllegalStateException(ex);
    		}
    		try {
    			if (context.isRunning()) {
    				Duration timeTakenToReady = Duration.ofNanos(System.nanoTime() - startTime);
    				listeners.ready(context, timeTakenToReady);
    			}
    		}
    		catch (Throwable ex) {
    			if (ex instanceof AbandonedRunException) {
    				throw ex;
    			}
    			handleRunFailure(context, ex, null);
    			throw new IllegalStateException(ex);
    		}
    		return context;
    	}

我们查看准备工作：

private void prepareContext(DefaultBootstrapContext bootstrapContext, ConfigurableApplicationContext context,
    			ConfigurableEnvironment environment, SpringApplicationRunListeners listeners,
    			ApplicationArguments applicationArguments, Banner printedBanner) {
    		context.setEnvironment(environment);
    		postProcessApplicationContext(context);
    		addAotGeneratedInitializerIfNecessary(this.initializers);
    		applyInitializers(context);
    		listeners.contextPrepared(context);
    		bootstrapContext.close(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 AbstractAutowireCapableBeanFactory autowireCapableBeanFactory) {
    			autowireCapableBeanFactory.setAllowCircularReferences(this.allowCircularReferences);
    			if (beanFactory instanceof DefaultListableBeanFactory listableBeanFactory) {
    				listableBeanFactory.setAllowBeanDefinitionOverriding(this.allowBeanDefinitionOverriding);
    			}
    		}
    		if (this.lazyInitialization) {
    			context.addBeanFactoryPostProcessor(new LazyInitializationBeanFactoryPostProcessor());
    		}
    		context.addBeanFactoryPostProcessor(new PropertySourceOrderingBeanFactoryPostProcessor(context));
    		if (!AotDetector.useGeneratedArtifacts()) {
    			// 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);
    	}

getAllSources获取入口类的信息。放到sources这个Set集合里边，然后去做load，我们查看load方法。

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();
    	}
    
    	void load() {
    		for (Object source : this.sources) {
    			load(source);
    		}
    	}
    
    private void load(Object source) {
    		Assert.notNull(source, "Source must not be null");
    		if (source instanceof Class<?> clazz) {
    			load(clazz);
    			return;
    		}
    		if (source instanceof Resource resource) {
    			load(resource);
    			return;
    		}
    		if (source instanceof Package pack) {
    			load(pack);
    			return;
    		}
    		if (source instanceof CharSequence sequence) {
    			load(sequence);
    			return;
    		}
    		throw new IllegalArgumentException("Invalid source type " + source.getClass());
    	}
    
    	private void 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);
    			((GroovyBeanDefinitionReader) this.groovyReader).beans(loader.getBeans());
    		}
    		if (isEligible(source)) {
    			this.annotatedReader.register(source);
    		}
    	}

到这里完成了一个重要的工作：读取入口类中重要的信息，包括注解包括入口类本身。将入口类中的注解注册到注解解读器annotationreader当中。

### 2：解析入口类注解到加载Bean ###

真正解析Bean的工作是从refreshContext当中进行的。

private void refreshContext(ConfigurableApplicationContext context) {
    		if (this.registerShutdownHook) {
    			shutdownHook.registerApplicationContext(context);
    		}
    		refresh(context);
    	}
    
    	protected void refresh(ConfigurableApplicationContext applicationContext) {
    		applicationContext.refresh();
    	}

最后跑到了一个applicationContext的refresh方法当中。

@Override
    	public void refresh() throws BeansException, IllegalStateException {
    		synchronized (this.startupShutdownMonitor) {
    			StartupStep contextRefresh = this.applicationStartup.start("spring.context.refresh");
    
    			// 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);
    
    				StartupStep beanPostProcess = this.applicationStartup.start("spring.context.beans.post-process");
    				// Invoke factory processors registered as beans in the context.
    				invokeBeanFactoryPostProcessors(beanFactory);
    
    				// Register bean processors that intercept bean creation.
    				registerBeanPostProcessors(beanFactory);
    				beanPostProcess.end();
    
    				// 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();
    				contextRefresh.end();
    			}
    		}
    	}

接下来会进行Bean处理的13方法，其中一个比较关键的方法：invokeBeanFactoryPostProcessors

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 (!NativeDetector.inNativeImage() && beanFactory.getTempClassLoader() == null &&
    				beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) {
    			beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));
    			beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
    		}
    	}

这里边会对我们的入口类中的注解进行详细的解析和复杂调用。其中对这些注解进行解析的时候，要用到了这么一个类：AutoConfigurationImportSelector

我们可以从调用链路上去证明这件事情：

"main@1" prio=5 tid=0x1 nid=NA runnable
      java.lang.Thread.State: RUNNABLE
    	  at org.springframework.boot.context.annotation.ImportCandidates.load(ImportCandidates.java:90)
    	  at org.springframework.boot.autoconfigure.AutoConfigurationImportSelector.getCandidateConfigurations(AutoConfigurationImportSelector.java:180)
    	  at org.springframework.boot.autoconfigure.AutoConfigurationImportSelector.getAutoConfigurationEntry(AutoConfigurationImportSelector.java:126)
    	  at org.springframework.boot.autoconfigure.AutoConfigurationImportSelector$AutoConfigurationGroup.process(AutoConfigurationImportSelector.java:430)
    	  at org.springframework.context.annotation.ConfigurationClassParser$DeferredImportSelectorGrouping.getImports(ConfigurationClassParser.java:796)
    	  at org.springframework.context.annotation.ConfigurationClassParser$DeferredImportSelectorGroupingHandler.processGroupImports(ConfigurationClassParser.java:726)
    	  at org.springframework.context.annotation.ConfigurationClassParser$DeferredImportSelectorHandler.process(ConfigurationClassParser.java:697)
    	  at org.springframework.context.annotation.ConfigurationClassParser.parse(ConfigurationClassParser.java:182)
    	  at org.springframework.context.annotation.ConfigurationClassPostProcessor.processConfigBeanDefinitions(ConfigurationClassPostProcessor.java:415)
    	  at org.springframework.context.annotation.ConfigurationClassPostProcessor.postProcessBeanDefinitionRegistry(ConfigurationClassPostProcessor.java:287)
    	  at org.springframework.context.support.PostProcessorRegistrationDelegate.invokeBeanDefinitionRegistryPostProcessors(PostProcessorRegistrationDelegate.java:344)
    	  at org.springframework.context.support.PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(PostProcessorRegistrationDelegate.java:115)
    	  at org.springframework.context.support.AbstractApplicationContext.invokeBeanFactoryPostProcessors(AbstractApplicationContext.java:779)
    	  at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:597)
    	  - locked <0x12a7> (a java.lang.Object)
    	  at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:146)
    	  at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:733)
    	  at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:435)
    	  at org.springframework.boot.SpringApplication.run(SpringApplication.java:311)
    	  at org.springframework.boot.SpringApplication.run(SpringApplication.java:1301)
    	  at org.springframework.boot.SpringApplication.run(SpringApplication.java:1290)
    	  at com.dashu.AlibabaApplication.main(AlibabaApplication.java:10)

所以，这个在自动装配的过程当中，确实完成了SpringSecurity的自动加载和配置。