spring ioc源码分析 | 易学教程

1.创建ApplicationContext

在上面spring boot启动中的分析中，发现在SpringApplication.run中创建了ApplicationContext 并且在context = this.createApplicationContext();中创建上下文

public ConfigurableApplicationContext run(String... args) {
        StopWatch stopWatch = new StopWatch();
        stopWatch.start();
        ConfigurableApplicationContext context = null;
        Collection<SpringBootExceptionReporter> exceptionReporters = new ArrayList();
        this.configureHeadlessProperty();
        SpringApplicationRunListeners listeners = this.getRunListeners(args);
        listeners.starting();

        Collection exceptionReporters;
        try {
            ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);
            ConfigurableEnvironment environment = this.prepareEnvironment(listeners, applicationArguments);
            this.configureIgnoreBeanInfo(environment);
            Banner printedBanner = this.printBanner(environment);
            //创建spring上下文
            context = this.createApplicationContext();
            exceptionReporters = this.getSpringFactoriesInstances(SpringBootExceptionReporter.class, new Class[]{ConfigurableApplicationContext.class}, context);
            this.prepareContext(context, environment, listeners, applicationArguments, printedBanner);
            //注入bean
            this.refreshContext(context);
            this.afterRefresh(context, applicationArguments);
            stopWatch.stop();
            if (this.logStartupInfo) {
                (new StartupInfoLogger(this.mainApplicationClass)).logStarted(this.getApplicationLog(), stopWatch);
            }

            listeners.started(context);
            this.callRunners(context, applicationArguments);
        } catch (Throwable var10) {
            this.handleRunFailure(context, var10, exceptionReporters, listeners);
            throw new IllegalStateException(var10);
        }

        try {
            listeners.running(context);
            return context;
        } catch (Throwable var9) {
            this.handleRunFailure(context, var9, exceptionReporters, (SpringApplicationRunListeners)null);
            throw new IllegalStateException(var9);
        }
    }

其中创建的ApplicationContext类型如下创建的类型为AnnotationConfigServletWebServerApplicationContext，所以ioc我们可以将断点打在AnnotationConfigApplicationContext中。

protected ConfigurableApplicationContext createApplicationContext() {
        Class<?> contextClass = this.applicationContextClass;
        if (contextClass == null) {
            try {
                switch(this.webApplicationType) {
                case SERVLET:
                    contextClass = Class.forName("org.springframework.boot.web.servlet.context.AnnotationConfigServletWebServerApplicationContext");
                    break;
                case REACTIVE:
                    contextClass = Class.forName("org.springframework.boot.web.reactive.context.AnnotationConfigReactiveWebServerApplicationContext");
                    break;
                default:
                    contextClass = Class.forName("org.springframework.context.annotation.AnnotationConfigApplicationContext");
                }
            } catch (ClassNotFoundException var3) {
                throw new IllegalStateException("Unable create a default ApplicationContext, please specify an ApplicationContextClass", var3);
            }
        }

        return (ConfigurableApplicationContext)BeanUtils.instantiateClass(contextClass);
    }

2 进入AbstractApplicationContext的refresh()方法

在refreshContext最终会调用AbstractApplicationContext的refresh方法

this.refreshContext(context);

@Override
public void refresh() throws BeansException, IllegalStateException {
    synchronized (this.startupShutdownMonitor) {
        // Prepare this context for refreshing.
        //刷新上下文环境
        prepareRefresh();
        // Tell the subclass to refresh the internal bean factory.
        //这里是在子类中启动 refreshBeanFactory() 的地方
        ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
        // Prepare the bean factory for use in this context.
        //准备bean工厂，以便在此上下文中使用
        prepareBeanFactory(beanFactory);
        try {
            // Allows post-processing of the bean factory in context subclasses.
            //设置 beanFactory 的后置处理
            postProcessBeanFactory(beanFactory);
            // Invoke factory processors registered as beans in the context.
            //调用 BeanFactory 的后处理器，这些处理器是在Bean 定义中向容器注册的
            invokeBeanFactoryPostProcessors(beanFactory);
            // Register bean processors that intercept bean creation.
            //注册Bean的后处理器，在Bean创建过程中调用
            registerBeanPostProcessors(beanFactory);
            // Initialize message source for this context.
            //对上下文中的消息源进行初始化
            initMessageSource();
            // Initialize event multicaster for this context.
            //初始化上下文中的事件机制
            initApplicationEventMulticaster();
            // Initialize other special beans in specific context subclasses.
            //初始化其他特殊的Bean
            onRefresh();
            // Check for listener beans and register them.
            //检查监听Bean并且将这些监听Bean向容器注册
            registerListeners();
            // Instantiate all remaining (non-lazy-init) singletons.
            //实例化所有的（non-lazy-init）单件
            finishBeanFactoryInitialization(beanFactory);
            // Last step: publish corresponding event.
            //发布容器事件，结束Refresh过程
            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();
        }
    }
}

（1）this.obtainFreshBeanFactory();装载初始化的bean

protected final void refreshBeanFactory() throws BeansException {
        if (this.hasBeanFactory()) {
            this.destroyBeans();
            this.closeBeanFactory();
        }

        try {
            //创建BeanFactory
            DefaultListableBeanFactory beanFactory = this.createBeanFactory();
            beanFactory.setSerializationId(this.getId());
            this.customizeBeanFactory(beanFactory);
            //载入bean
            this.loadBeanDefinitions(beanFactory);
            synchronized(this.beanFactoryMonitor) {
                this.beanFactory = beanFactory;
            }
        } catch (IOException var5) {
            throw new ApplicationContextException("I/O error parsing bean definition source for " + this.getDisplayName(), var5);
        }
    }

（2）this.prepareBeanFactory(beanFactory);

protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {
        //添加类加载器
        beanFactory.setBeanClassLoader(this.getClassLoader());
         // 配置EL表达式
        beanFactory.setBeanExpressionResolver(new StandardBeanExpressionResolver(beanFactory.getBeanClassLoader()));
        // 添加属性编辑器 PropertyEditor
        beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, this.getEnvironment()));
        //添加后置处理器
        beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));
        
        //忽略以下类
        beanFactory.ignoreDependencyInterface(EnvironmentAware.class);
        beanFactory.ignoreDependencyInterface(EmbeddedValueResolverAware.class);
        beanFactory.ignoreDependencyInterface(ResourceLoaderAware.class);
        beanFactory.ignoreDependencyInterface(ApplicationEventPublisherAware.class);
        beanFactory.ignoreDependencyInterface(MessageSourceAware.class);
        beanFactory.ignoreDependencyInterface(ApplicationContextAware.class);
        
        //放入resolvableDependencies属性
        beanFactory.registerResolvableDependency(BeanFactory.class, beanFactory);
        beanFactory.registerResolvableDependency(ResourceLoader.class, this);
        beanFactory.registerResolvableDependency(ApplicationEventPublisher.class, this);
        beanFactory.registerResolvableDependency(ApplicationContext.class, this);
        beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(this));
        if (beanFactory.containsBean("loadTimeWeaver")) {
            beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));
            beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
        }
 
        //以下为单例
        if (!beanFactory.containsLocalBean("environment")) {
            beanFactory.registerSingleton("environment", this.getEnvironment());
        }

        if (!beanFactory.containsLocalBean("systemProperties")) {
            beanFactory.registerSingleton("systemProperties", this.getEnvironment().getSystemProperties());
        }

        if (!beanFactory.containsLocalBean("systemEnvironment")) {
            beanFactory.registerSingleton("systemEnvironment", this.getEnvironment().getSystemEnvironment());
        }

    }

（3）postProcessBeanFactory

postProcessBeanFactory()方法向上下文中添加了一系列的Bean的后置处理器。后置处理器工作的时机是在所有的beanDenifition加载完成之后，bean实例化之前执行。简单来说Bean的后置处理器可以修改BeanDefinition的属性信息。

（4）invokeBeanFactoryPostProcessors-->parse

public void refresh() throws BeansException, IllegalStateException {
                     ...
                this.invokeBeanFactoryPostProcessors(beanFactory);
                     ...
    }



protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {
        PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory, this.getBeanFactoryPostProcessors());
                     ...

    }


 public static void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {
                     ...

                              invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
                currentRegistryProcessors.clear();
                     ...
    }


private static void invokeBeanDefinitionRegistryPostProcessors(Collection<? extends BeanDefinitionRegistryPostProcessor> postProcessors, 
                    ...

            postProcessor.postProcessBeanDefinitionRegistry(registry);
        

    }


public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) {
                   ...
            this.processConfigBeanDefinitions(registry);
                   ...
    }


public void processConfigBeanDefinitions(BeanDefinitionRegistry registry) {
                   ...
                parser.parse(candidates);
                   ...
    }

 // ConfigurationClassParser类
public void parse(Set<BeanDefinitionHolder> configCandidates) {
        Iterator var2 = configCandidates.iterator();

        while(var2.hasNext()) {
            BeanDefinitionHolder holder = (BeanDefinitionHolder)var2.next();
            BeanDefinition bd = holder.getBeanDefinition();

            try {
                //SpringBoot项目项目启动时AnnotatedBeanDefinition 上面注入的启动类的BeanDefinition
                if (bd instanceof AnnotatedBeanDefinition) {
                    this.parse(((AnnotatedBeanDefinition)bd).getMetadata(), holder.getBeanName());
                } else if (bd instanceof AbstractBeanDefinition && ((AbstractBeanDefinition)bd).hasBeanClass()) {
                    this.parse(((AbstractBeanDefinition)bd).getBeanClass(), holder.getBeanName());
                } else {
                    this.parse(bd.getBeanClassName(), holder.getBeanName());
                }
            } catch (BeanDefinitionStoreException var6) {
                throw var6;
            } catch (Throwable var7) {
                throw new BeanDefinitionStoreException("Failed to parse configuration class [" + bd.getBeanClassName() + "]", var7);
            }
        
        // 加载默认的配置 就是加载.pom中的的依赖 
        this.deferredImportSelectorHandler.process();
    }

protected final void parse(AnnotationMetadata metadata, String beanName) throws IOException {
        this.processConfigurationClass(new ConfigurationClass(metadata, beanName));
    }



protected void processConfigurationClass(ConfigurationClass configClass) throws IOException {
              ...

            do {
                //递归处理Bean，如果有父类，递归处理，直到顶层父类
                sourceClass = this.doProcessConfigurationClass(configClass, sourceClass);
            }
              ...
        }
    }



// ConfigurationClassParser类
         protected final SourceClass doProcessConfigurationClass(ConfigurationClass configClass, SourceClass sourceClass)
                throws IOException {
        
            // Recursively process any member (nested) classes first
            //首先递归处理内部类，（SpringBoot项目的主类一般没有内部类）
            processMemberClasses(configClass, sourceClass);
        
            // Process any @PropertySource annotations
            // 针对 @PropertySource 注解的属性配置处理
            for (AnnotationAttributes propertySource : AnnotationConfigUtils.attributesForRepeatable(
                    sourceClass.getMetadata(), PropertySources.class,
                    org.springframework.context.annotation.PropertySource.class)) {
                if (this.environment instanceof ConfigurableEnvironment) {
                    processPropertySource(propertySource);
                } else {
                    logger.warn("Ignoring @PropertySource annotation on [" + sourceClass.getMetadata().getClassName() +
                            "]. Reason: Environment must implement ConfigurableEnvironment");
                }
            }
        
            // Process any @ComponentScan annotations
            // 根据 @ComponentScan 注解，扫描项目中的Bean（SpringBoot 启动类上有该注解）
            Set<AnnotationAttributes> componentScans = AnnotationConfigUtils.attributesForRepeatable(
                    sourceClass.getMetadata(), ComponentScans.class, ComponentScan.class);
            if (!componentScans.isEmpty() &&
                    !this.conditionEvaluator.shouldSkip(sourceClass.getMetadata(), ConfigurationPhase.REGISTER_BEAN)) {
                for (AnnotationAttributes componentScan : componentScans) {
                    // The config class is annotated with @ComponentScan -> perform the scan immediately
                    // 立即执行扫描，（SpringBoot项目为什么是从主类所在的包扫描，这就是关键了）
                    Set<BeanDefinitionHolder> scannedBeanDefinitions =
                            this.componentScanParser.parse(componentScan, sourceClass.getMetadata().getClassName());
                    // Check the set of scanned definitions for any further config classes and parse recursively if needed
                    for (BeanDefinitionHolder holder : scannedBeanDefinitions) {
                        BeanDefinition bdCand = holder.getBeanDefinition().getOriginatingBeanDefinition();
                        if (bdCand == null) {
                            bdCand = holder.getBeanDefinition();
                        }
                        // 检查是否是ConfigurationClass（是否有configuration/component两个注解），如果是，递归查找该类相关联的配置类。
                        // 所谓相关的配置类，比如@Configuration中的@Bean定义的bean。或者在有@Component注解的类上继续存在@Import注解。
                        if (ConfigurationClassUtils.checkConfigurationClassCandidate(bdCand, this.metadataReaderFactory)) {
                            parse(bdCand.getBeanClassName(), holder.getBeanName());
                        }
                    }
                }
            }
        
            // Process any @Import annotations
            //递归处理 @Import 注解（SpringBoot项目中经常用的各种@Enable*** 注解基本都是封装的@Import）
            processImports(configClass, sourceClass, getImports(sourceClass), true);
        
            // Process any @ImportResource annotations
            AnnotationAttributes importResource =
                    AnnotationConfigUtils.attributesFor(sourceClass.getMetadata(), ImportResource.class);
            if (importResource != null) {
                String[] resources = importResource.getStringArray("locations");
                Class<? extends BeanDefinitionReader> readerClass = importResource.getClass("reader");
                for (String resource : resources) {
                    String resolvedResource = this.environment.resolveRequiredPlaceholders(resource);
                    configClass.addImportedResource(resolvedResource, readerClass);
                }
            }
        
            // Process individual @Bean methods
            Set<MethodMetadata> beanMethods = retrieveBeanMethodMetadata(sourceClass);
            for (MethodMetadata methodMetadata : beanMethods) {
                configClass.addBeanMethod(new BeanMethod(methodMetadata, configClass));
            }
        
            // Process default methods on interfaces
            processInterfaces(configClass, sourceClass);
        
            // Process superclass, if any
            if (sourceClass.getMetadata().hasSuperClass()) {
                String superclass = sourceClass.getMetadata().getSuperClassName();
                if (superclass != null && !superclass.startsWith("java") &&
                        !this.knownSuperclasses.containsKey(superclass)) {
                    this.knownSuperclasses.put(superclass, configClass);
                    // Superclass found, return its annotation metadata and recurse
                    return sourceClass.getSuperClass();
                }
             }
        
             // No superclass -> processing is complete
             return null;
         }

进入Set<BeanDefinitionHolder> scannedBeanDefinitions = this.componentScanParser.parse(componentScan, sourceClass.getMetadata().getClassName());

public Set<BeanDefinitionHolder> parse(AnnotationAttributes componentScan, final String declaringClass) {
                  ...
        return scanner.doScan(StringUtils.toStringArray(basePackages));
    }



protected Set<BeanDefinitionHolder> doScan(String... basePackages) {
       

        for(int var5 = 0; var5 < var4; ++var5) {
            String basePackage = var3[var5];
            //扫描注解 查到bean 转为BeanDefinition
            Set<BeanDefinition> candidates = this.findCandidateComponents(basePackage);
            Iterator var8 = candidates.iterator();

            while(var8.hasNext()) {
                BeanDefinition candidate = (BeanDefinition)var8.next();
                ScopeMetadata scopeMetadata = this.scopeMetadataResolver.resolveScopeMetadata(candidate);
                candidate.setScope(scopeMetadata.getScopeName());
                String beanName = this.beanNameGenerator.generateBeanName(candidate, this.registry);
                if (candidate instanceof AbstractBeanDefinition) {
                    this.postProcessBeanDefinition((AbstractBeanDefinition)candidate, beanName);
                }

                if (candidate instanceof AnnotatedBeanDefinition) {
                    AnnotationConfigUtils.processCommonDefinitionAnnotations((AnnotatedBeanDefinition)candidate);
                }

                if (this.checkCandidate(beanName, candidate)) {
                    BeanDefinitionHolder definitionHolder = new BeanDefinitionHolder(candidate, beanName);
                    definitionHolder = AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry);
                    beanDefinitions.add(definitionHolder);
                    //注入ioc
                    this.registerBeanDefinition(definitionHolder, this.registry);
                }
            }
        }

        return beanDefinitions;
    }

个人理解：获取bean的过程

1)：获取要扫描的包的地址

2)：通过注解扫描出bean

3):BeanDefinitionReaderUtils.registerBeanDefinition(definitionHolder, this.registry);将该BeanDefinition注册到IoC容器的beanDefinitionMap中

public static void registerBeanDefinition(BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry) throws BeanDefinitionStoreException {
        String beanName = definitionHolder.getBeanName();
        registry.registerBeanDefinition(beanName, definitionHolder.getBeanDefinition());
        String[] aliases = definitionHolder.getAliases();
        if (aliases != null) {
            String[] var4 = aliases;
            int var5 = aliases.length;

            for(int var6 = 0; var6 < var5; ++var6) {
                String alias = var4[var6];
                registry.registerAlias(beanName, alias);
            }
        }

    }

其中在 parse 中的 this.deferredImportSelectorHandler.process(); 加载pom文件中的依赖

https://juejin.im/post/5dad23685188251d2c4ea2b6

百度上的答案是：

实例化Bean对象，这个时候Bean的对象是非常低级的，基本不能够被我们使用，因为连最基本的属性都没有设置，可以理解为连Autowired注解都是没有解析的；
填充属性，当做完这一步，Bean对象基本是完整的了，可以理解为Autowired注解已经解析完毕，依赖注入完成了；
如果Bean实现了BeanNameAware接口，则调用setBeanName方法；
如果Bean实现了BeanClassLoaderAware接口，则调用setBeanClassLoader方法；
如果Bean实现了BeanFactoryAware接口，则调用setBeanFactory方法；
调用BeanPostProcessor的postProcessBeforeInitialization方法；
如果Bean实现了InitializingBean接口，调用afterPropertiesSet方法；
如果Bean定义了init-method方法，则调用Bean的init-method方法；
调用BeanPostProcessor的postProcessAfterInitialization方法；当进行到这一步，Bean已经被准备就绪了，一直停留在应用的上下文中，直到被销毁；
如果应用的上下文被销毁了，如果Bean实现了DisposableBean接口，则调用destroy方法，如果Bean定义了destory-method声明了销毁方法也会被调用。