1. 简介
IOC:Inversion of Control 也称为依赖倒置原理(Dependency Inversion Principle):对象依赖关系的管理被反转了，对象之间的依赖关系由IoC容器进行管理，并且IoC完成对象的注入。
SpringIoC：包含了最为基本的IoC容器BeanFactory的接口与实现。比如XmlBeanFactory 就是一个最基本的BeanFactory(IoC容器)。BeanFactory是一个简单容器系列，只实现了容器基本的功能；另一个是ApplicationContext 上下文，它作为容器的高级形态存在，继承自BeanFactory并增加了许多面向框架的特性，同时对应用环境作了许多适配。
BeanFactory源码如下：
package org.springframework.beans.factory; import org.springframework.beans.BeansException; import org.springframework.core.ResolvableType; import org.springframework.lang.Nullable; public interface BeanFactory { String FACTORY_BEAN_PREFIX = "&"; Object getBean(String var1) throws BeansException; <T> T getBean(String var1, Class<T> var2) throws BeansException; Object getBean(String var1, Object... var2) throws BeansException; <T> T getBean(Class<T> var1) throws BeansException; <T> T getBean(Class<T> var1, Object... var2) throws BeansException; <T> ObjectProvider<T> getBeanProvider(Class<T> var1); <T> ObjectProvider<T> getBeanProvider(ResolvableType var1); boolean containsBean(String var1); boolean isSingleton(String var1) throws NoSuchBeanDefinitionException; boolean isPrototype(String var1) throws NoSuchBeanDefinitionException; boolean isTypeMatch(String var1, ResolvableType var2) throws NoSuchBeanDefinitionException; boolean isTypeMatch(String var1, Class<?> var2) throws NoSuchBeanDefinitionException; @Nullable Class<?> getType(String var1) throws NoSuchBeanDefinitionException; @Nullable Class<?> getType(String var1, boolean var2) throws NoSuchBeanDefinitionException; String[] getAliases(String var1); }
在Spring提供的基本Ioc容器的接口定义和实现的基础上，Spring通过定义BeanDefinition来管理基于Spring的应用中的各种对象以及它们之间的相互依赖关系。BeanDefinition抽象了我们对Bean
的定义，是让容器起作用的主要数据类型。BeanDefinition中维持了Bean是否是单例、是否Primary、是否Lazy等属性。源码如下：
// // Source code recreated from a .class file by IntelliJ IDEA // (powered by FernFlower decompiler) // package org.springframework.beans.factory.config; import org.springframework.beans.BeanMetadataElement; import org.springframework.beans.MutablePropertyValues; import org.springframework.core.AttributeAccessor; import org.springframework.core.ResolvableType; import org.springframework.lang.Nullable; public interface BeanDefinition extends AttributeAccessor, BeanMetadataElement { String SCOPE_SINGLETON = "singleton"; String SCOPE_PROTOTYPE = "prototype"; int ROLE_APPLICATION = 0; int ROLE_SUPPORT = 1; int ROLE_INFRASTRUCTURE = 2; void setParentName(@Nullable String var1); @Nullable String getParentName(); void setBeanClassName(@Nullable String var1); @Nullable String getBeanClassName(); void setScope(@Nullable String var1); @Nullable String getScope(); void setLazyInit(boolean var1); boolean isLazyInit(); void setDependsOn(@Nullable String... var1); @Nullable String[] getDependsOn(); void setAutowireCandidate(boolean var1); boolean isAutowireCandidate(); void setPrimary(boolean var1); boolean isPrimary(); void setFactoryBeanName(@Nullable String var1); @Nullable String getFactoryBeanName(); void setFactoryMethodName(@Nullable String var1); @Nullable String getFactoryMethodName(); ConstructorArgumentValues getConstructorArgumentValues(); default boolean hasConstructorArgumentValues() { return !this.getConstructorArgumentValues().isEmpty(); } MutablePropertyValues getPropertyValues(); default boolean hasPropertyValues() { return !this.getPropertyValues().isEmpty(); } void setInitMethodName(@Nullable String var1); @Nullable String getInitMethodName(); void setDestroyMethodName(@Nullable String var1); @Nullable String getDestroyMethodName(); void setRole(int var1); int getRole(); void setDescription(@Nullable String var1); @Nullable String getDescription(); ResolvableType getResolvableType(); boolean isSingleton(); boolean isPrototype(); boolean isAbstract(); @Nullable String getResourceDescription(); @Nullable BeanDefinition getOriginatingBeanDefinition(); }
在Spring具体的注入实现中，接口注入、setter注入、构造器注入是主要的注入方式。在Spring的IOC设计中，setter注入和构造器注入是主要的注入方式；相对而言，使用spring时setter注入
是常见的注入方式，而且为了防止注入异常，spring IOC容器还提供了对特定依赖的检查。
1. IoC容器设计
主要类图如下：
可以看到有两条线路：
第一条是： BeanFactory到HierarchicalBeanFactory再到ConfigurableBeanFactory。在这条路线中，BeanFactory定义了接口的IoC容器的规范，HierarchicalBeanFactory 继承BeanFactory切增加了getParentBeanFactory方法，是的BeanFactory具备了双亲IoC容器的管理功能。在ConfigurableBeanFactory主要定义了一些对BeanFactory的配置功能，比如setParentBeanFactory 设置双亲IoC容器，通过addBeanPostProcessor 配置Bean后置处理器等。
第二条：以ApplicationContext为主。这里主要是从BeanFactory到ListableBeanFactory，再到ApplicationContext，再到常用的ConfigurableApplicationContext或者WebApplicationContext。ApplicationCeontext通过继承MessageSource、ApplicationEventPublisher、ResourcePatternResolver 添加了许多对高级容器的特性的支持。
1. BeanFactory应用场景以及设计原理
用户使用容器时，可以使用转义符"&" 来得到FactoryBean 本身，用来区分FacrotyBean产生的对象和FactoryBean本身。举例来说，如果myJndiObject是一个FactoryBean，那么使用
&myJndiObject 得到的是FactoryBean而不是myJndiObject 这个FactoryBean产生出来的对象。FactoryBean 默认是只生成工程Bean，在使用bean的时候才会生成bean。可以 SmartFactoryBean 的 isEagerInit 来进行控制，为true则在生成FactoryBean的时候调用工厂的getObject方法生成Bean。
BeanFactory是个Factory，也就是IOC容器或对象工厂，FactoryBean是个Bean。在Spring中，所有的Bean都是由BeanFactory(也就是IOC容器)来进行管理的。但对FactoryBean而言，这个
Bean不是简单的Bean，而是一个能生产或者修饰对象生成的工厂Bean,它的实现与设计模式中的工厂模式和修饰器模式类似。
BeanFactory提供了使用IoC容器的规范。在这个基础上，Spring还提供了一些容器的实现供开发人员使用，以XmlBeanFactory为例来说明IoC容器的设计原理。XmlBeanFactory 类图如下：
XmlBeanFactory 继承自DefaultListableBeanFactory， DefaultListableBeanFactory 可以作为一个默认的功能完整的IoC容器来使用。XmlBeanFactory 在其基础上增加了新的功能-读取XML
文件方式定义的BeanDefinition。其源码如下：
public class XmlBeanFactory extends DefaultListableBeanFactory { private final XmlBeanDefinitionReader reader; public XmlBeanFactory(Resource resource) throws BeansException { this(resource, (BeanFactory)null); } public XmlBeanFactory(Resource resource, BeanFactory parentBeanFactory) throws BeansException { super(parentBeanFactory); this.reader = new XmlBeanDefinitionReader(this); this.reader.loadBeanDefinitions(resource); } }
XmlBeanFactory 构造时需要指定BeanDefinition 的信息来源，而这个信息需要封装成 Spring的Resource类来给出。从源码可以看出在构造方法中得到Resource对象以及使用这个对象来完成
loadBeanDefinitions 的调用，这个方法也是IoC容器初始化的重要组成部分。
编程式的IoC容器使用如下：
ClassPathResource classPathResource = new ClassPathResource("beans.xml"); DefaultListableBeanFactory defaultListableBeanFactory = new DefaultListableBeanFactory(); XmlBeanDefinitionReader xmlBeanDefinitionReader = new XmlBeanDefinitionReader(defaultListableBeanFactory); xmlBeanDefinitionReader.loadBeanDefinitions(classPathResource);
(1) 创建IoC配置文件的抽象资源，这个抽象资源包含了BeanDefinition的定义信息
(2)创建一个BeanDefactory，这里使用默认的DefaultListableBeanDactory
(3)创建一个载入BeanDefinition的读取器，这里使用XmlBeanDefinitionReader
(4)从定义好的资源位置读取配置信息，具体的解析过程由XmlBeanDefinitionReader 来完成。完成整个载入和注册Bean定义之后，IoC容器就建立起来了，这个时候就可以使用IoC容器了。
XmlBeanDefinitionReader .loadBeanDefinitions 过程如下：
1》 交给重载的loadBeanDefinitions(EncodedResource encodedResource) 方法，方法内部获取到资源后调用doLoadBeanDefinitions 做具体的操作
public int loadBeanDefinitions(Resource resource) throws BeanDefinitionStoreException { return this.loadBeanDefinitions(new EncodedResource(resource)); } public int loadBeanDefinitions(EncodedResource encodedResource) throws BeanDefinitionStoreException { Assert.notNull(encodedResource, "EncodedResource must not be null"); if (this.logger.isTraceEnabled()) { this.logger.trace("Loading XML bean definitions from " + encodedResource); } Set<EncodedResource> currentResources = (Set)this.resourcesCurrentlyBeingLoaded.get(); if (currentResources == null) { currentResources = new HashSet(4); this.resourcesCurrentlyBeingLoaded.set(currentResources); } if (!((Set)currentResources).add(encodedResource)) { throw new BeanDefinitionStoreException("Detected cyclic loading of " + encodedResource + " - check your import definitions!"); } else { int var5; try { InputStream inputStream = encodedResource.getResource().getInputStream(); try { InputSource inputSource = new InputSource(inputStream); if (encodedResource.getEncoding() != null) { inputSource.setEncoding(encodedResource.getEncoding()); } var5 = this.doLoadBeanDefinitions(inputSource, encodedResource.getResource()); } finally { inputStream.close(); } } catch (IOException var15) { throw new BeanDefinitionStoreException("IOException parsing XML document from " + encodedResource.getResource(), var15); } finally { ((Set)currentResources).remove(encodedResource); if (((Set)currentResources).isEmpty()) { this.resourcesCurrentlyBeingLoaded.remove(); } } return var5; } }
2》doLoadBeanDefinitions 方法内部先调用 doLoadDocument 先构建Document对象(XML 文档树)； 然后调用registerBeanDefinitions 注册BeanDefinition信息
protected int doLoadBeanDefinitions(InputSource inputSource, Resource resource) throws BeanDefinitionStoreException { try { Document doc = this.doLoadDocument(inputSource, resource); int count = this.registerBeanDefinitions(doc, resource); if (this.logger.isDebugEnabled()) { this.logger.debug("Loaded " + count + " bean definitions from " + resource); } return count; } catch (BeanDefinitionStoreException var5) { throw var5; } catch (SAXParseException var6) { throw new XmlBeanDefinitionStoreException(resource.getDescription(), "Line " + var6.getLineNumber() + " in XML document from " + resource + " is invalid", var6); } catch (SAXException var7) { throw new XmlBeanDefinitionStoreException(resource.getDescription(), "XML document from " + resource + " is invalid", var7); } catch (ParserConfigurationException var8) { throw new BeanDefinitionStoreException(resource.getDescription(), "Parser configuration exception parsing XML from " + resource, var8); } catch (IOException var9) { throw new BeanDefinitionStoreException(resource.getDescription(), "IOException parsing XML document from " + resource, var9); } catch (Throwable var10) { throw new BeanDefinitionStoreException(resource.getDescription(), "Unexpected exception parsing XML document from " + resource, var10); } }
3》registerBeanDefinitions 方法内部先构造了BeanDefinitionDocumentReader 对象，然后交给BeanDefinitionDocumentReader 注册完BeanDefinition之后减去注册之前的数量返回结果
public int registerBeanDefinitions(Document doc, Resource resource) throws BeanDefinitionStoreException { BeanDefinitionDocumentReader documentReader = this.createBeanDefinitionDocumentReader(); int countBefore = this.getRegistry().getBeanDefinitionCount(); documentReader.registerBeanDefinitions(doc, this.createReaderContext(resource)); return this.getRegistry().getBeanDefinitionCount() - countBefore; }
3.1 》 getBeanDefinitionCount 是父类DefaultListableBeanFactory 的一个方法，其逻辑是返回beanDefinitionMap 的大小(这也证实了IoC的对象是存在一个Map里面)
private final Map<String, BeanDefinition> beanDefinitionMap = new ConcurrentHashMap(256); public int getBeanDefinitionCount() { return this.beanDefinitionMap.size(); }
3.2》createReaderContext 方法构造了一个XmlReaderContext 对象，用于包装注册时的上下文
public XmlReaderContext createReaderContext(Resource resource) { return new XmlReaderContext(resource, this.problemReporter, this.eventListener, this.sourceExtractor, this, this.getNamespaceHandlerResolver()); }
3.3》DefaultBeanDefinitionDocumentReader#registerBeanDefinitions是注册BeanDefinition的重点，doRegisterBeanDefinitions 是核心方法
public void registerBeanDefinitions(Document doc, XmlReaderContext readerContext) { this.readerContext = readerContext; this.doRegisterBeanDefinitions(doc.getDocumentElement()); }
3.3.1》doRegisterBeanDefinitions 方法如下， 核心交给parseBeanDefinitions方法
protected void doRegisterBeanDefinitions(Element root) { // Any nested <beans> elements will cause recursion in this method. In // order to propagate and preserve <beans> default-* attributes correctly, // keep track of the current (parent) delegate, which may be null. Create // the new (child) delegate with a reference to the parent for fallback purposes, // then ultimately reset this.delegate back to its original (parent) reference. // this behavior emulates a stack of delegates without actually necessitating one. BeanDefinitionParserDelegate parent = this.delegate; this.delegate = createDelegate(getReaderContext(), root, parent); if (this.delegate.isDefaultNamespace(root)) { String profileSpec = root.getAttribute(PROFILE_ATTRIBUTE); if (StringUtils.hasText(profileSpec)) { String[] specifiedProfiles = StringUtils.tokenizeToStringArray( profileSpec, BeanDefinitionParserDelegate.MULTI_VALUE_ATTRIBUTE_DELIMITERS); // We cannot use Profiles.of(...) since profile expressions are not supported // in XML config. See SPR-12458 for details. if (!getReaderContext().getEnvironment().acceptsProfiles(specifiedProfiles)) { if (logger.isDebugEnabled()) { logger.debug("Skipped XML bean definition file due to specified profiles [" + profileSpec + "] not matching: " + getReaderContext().getResource()); } return; } } } preProcessXml(root); parseBeanDefinitions(root, this.delegate); postProcessXml(root); this.delegate = parent; }
3.3.2》parseBeanDefinitions 方法
/** * Parse the elements at the root level in the document: * "import", "alias", "bean". * @param root the DOM root element of the document */ protected void parseBeanDefinitions(Element root, BeanDefinitionParserDelegate delegate) { if (delegate.isDefaultNamespace(root)) { NodeList nl = root.getChildNodes(); for (int i = 0; i < nl.getLength(); i++) { Node node = nl.item(i); if (node instanceof Element) { Element ele = (Element) node; if (delegate.isDefaultNamespace(ele)) { parseDefaultElement(ele, delegate); } else { delegate.parseCustomElement(ele); } } } } else { delegate.parseCustomElement(root); } }
3.3.3》parseDefaultElement 方法如下：BEAN_ELEMENT的"bean" 元素，对应的在org.springframework.beans.factory.xml.BeanDefinitionParserDelegate#BEAN_ELEMENT 中维护
private void parseDefaultElement(Element ele, BeanDefinitionParserDelegate delegate) { if (delegate.nodeNameEquals(ele, IMPORT_ELEMENT)) { importBeanDefinitionResource(ele); } else if (delegate.nodeNameEquals(ele, ALIAS_ELEMENT)) { processAliasRegistration(ele); } else if (delegate.nodeNameEquals(ele, BEAN_ELEMENT)) { processBeanDefinition(ele, delegate); } else if (delegate.nodeNameEquals(ele, NESTED_BEANS_ELEMENT)) { // recurse doRegisterBeanDefinitions(ele); } }
3.3.4》 查看解析bean 元素的processBeanDefinition 方法如下
protected void processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate) { BeanDefinitionHolder bdHolder = delegate.parseBeanDefinitionElement(ele); if (bdHolder != null) { bdHolder = delegate.decorateBeanDefinitionIfRequired(ele, bdHolder); try { // Register the final decorated instance. BeanDefinitionReaderUtils.registerBeanDefinition(bdHolder, getReaderContext().getRegistry()); } catch (BeanDefinitionStoreException ex) { getReaderContext().error("Failed to register bean definition with name '" + bdHolder.getBeanName() + "'", ele, ex); } // Send registration event. getReaderContext().fireComponentRegistered(new BeanComponentDefinition(bdHolder)); } }
第一步创建BeanDefinitionHolder 维护信息：org.springframework.beans.factory.xml.BeanDefinitionParserDelegate#parseBeanDefinitionElement(org.w3c.dom.Element) 创建BeanDefinitionHolder相关信息：其实Holder就是维护了BeanDefinition信息和bean的name等信息
/** * Parses the supplied {@code <bean>} element. May return {@code null} * if there were errors during parse. Errors are reported to the * {@link org.springframework.beans.factory.parsing.ProblemReporter}. */ @Nullable public BeanDefinitionHolder parseBeanDefinitionElement(Element ele) { return parseBeanDefinitionElement(ele, null); } /** * Parses the supplied {@code <bean>} element. May return {@code null} * if there were errors during parse. Errors are reported to the * {@link org.springframework.beans.factory.parsing.ProblemReporter}. */ @Nullable public BeanDefinitionHolder parseBeanDefinitionElement(Element ele, @Nullable BeanDefinition containingBean) { String id = ele.getAttribute(ID_ATTRIBUTE); String nameAttr = ele.getAttribute(NAME_ATTRIBUTE); List<String> aliases = new ArrayList<>(); if (StringUtils.hasLength(nameAttr)) { String[] nameArr = StringUtils.tokenizeToStringArray(nameAttr, MULTI_VALUE_ATTRIBUTE_DELIMITERS); aliases.addAll(Arrays.asList(nameArr)); } String beanName = id; if (!StringUtils.hasText(beanName) && !aliases.isEmpty()) { beanName = aliases.remove(0); if (logger.isTraceEnabled()) { logger.trace("No XML 'id' specified - using '" + beanName + "' as bean name and " + aliases + " as aliases"); } } if (containingBean == null) { checkNameUniqueness(beanName, aliases, ele); } AbstractBeanDefinition beanDefinition = parseBeanDefinitionElement(ele, beanName, containingBean); if (beanDefinition != null) { if (!StringUtils.hasText(beanName)) { try { if (containingBean != null) { beanName = BeanDefinitionReaderUtils.generateBeanName( beanDefinition, this.readerContext.getRegistry(), true); } else { beanName = this.readerContext.generateBeanName(beanDefinition); // Register an alias for the plain bean class name, if still possible, // if the generator returned the class name plus a suffix. // This is expected for Spring 1.2/2.0 backwards compatibility. String beanClassName = beanDefinition.getBeanClassName(); if (beanClassName != null && beanName.startsWith(beanClassName) && beanName.length() > beanClassName.length() && !this.readerContext.getRegistry().isBeanNameInUse(beanClassName)) { aliases.add(beanClassName); } } if (logger.isTraceEnabled()) { logger.trace("Neither XML 'id' nor 'name' specified - " + "using generated bean name [" + beanName + "]"); } } catch (Exception ex) { error(ex.getMessage(), ele); return null; } } String[] aliasesArray = StringUtils.toStringArray(aliases); return new BeanDefinitionHolder(beanDefinition, beanName, aliasesArray); } return null; }
第二步交给org.springframework.beans.factory.support.BeanDefinitionReaderUtils#registerBeanDefinition进行注册，BeanDefinitionRegistry 是一开始创建的DefaultBeanFactory，在创建XmlBeanDefinitionReader 的时候维护。
/** * Register the given bean definition with the given bean factory. * @param definitionHolder the bean definition including name and aliases * @param registry the bean factory to register with * @throws BeanDefinitionStoreException if registration failed */ public static void registerBeanDefinition( BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry) throws BeanDefinitionStoreException { // Register bean definition under primary name. String beanName = definitionHolder.getBeanName(); registry.registerBeanDefinition(beanName, definitionHolder.getBeanDefinition()); // Register aliases for bean name, if any. String[] aliases = definitionHolder.getAliases(); if (aliases != null) { for (String alias : aliases) { registry.registerAlias(beanName, alias); } } }
核心是registry.registerBeanDefinition。经过一圈处理加工之后最后回到org.springframework.beans.factory.support.DefaultListableBeanFactory#registerBeanDefinition，源码如下：可以看到进行了一系列判断，验证是否已经存在等信息，如果不存在将BeanDefinition加入到beanDefinitionMap(ConcurrentHashMap)，并且将bean的name加入到beanDefinitionNames（ArrayList）
@Override public void registerBeanDefinition(String beanName, BeanDefinition beanDefinition) throws BeanDefinitionStoreException { Assert.hasText(beanName, "Bean name must not be empty"); Assert.notNull(beanDefinition, "BeanDefinition must not be null"); if (beanDefinition instanceof AbstractBeanDefinition) { try { ((AbstractBeanDefinition) beanDefinition).validate(); } catch (BeanDefinitionValidationException ex) { throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName, "Validation of bean definition failed", ex); } } BeanDefinition existingDefinition = this.beanDefinitionMap.get(beanName); if (existingDefinition != null) { if (!isAllowBeanDefinitionOverriding()) { throw new BeanDefinitionOverrideException(beanName, beanDefinition, existingDefinition); } else if (existingDefinition.getRole() < beanDefinition.getRole()) { // e.g. was ROLE_APPLICATION, now overriding with ROLE_SUPPORT or ROLE_INFRASTRUCTURE if (logger.isInfoEnabled()) { logger.info("Overriding user-defined bean definition for bean '" + beanName + "' with a framework-generated bean definition: replacing [" + existingDefinition + "] with [" + beanDefinition + "]"); } } else if (!beanDefinition.equals(existingDefinition)) { if (logger.isDebugEnabled()) { logger.debug("Overriding bean definition for bean '" + beanName + "' with a different definition: replacing [" + existingDefinition + "] with [" + beanDefinition + "]"); } } else { if (logger.isTraceEnabled()) { logger.trace("Overriding bean definition for bean '" + beanName + "' with an equivalent definition: replacing [" + existingDefinition + "] with [" + beanDefinition + "]"); } } this.beanDefinitionMap.put(beanName, beanDefinition); } else { if (hasBeanCreationStarted()) { // Cannot modify startup-time collection elements anymore (for stable iteration) synchronized (this.beanDefinitionMap) { this.beanDefinitionMap.put(beanName, beanDefinition); List<String> updatedDefinitions = new ArrayList<>(this.beanDefinitionNames.size() + 1); updatedDefinitions.addAll(this.beanDefinitionNames); updatedDefinitions.add(beanName); this.beanDefinitionNames = updatedDefinitions; removeManualSingletonName(beanName); } } else { // Still in startup registration phase this.beanDefinitionMap.put(beanName, beanDefinition); this.beanDefinitionNames.add(beanName); removeManualSingletonName(beanName); } this.frozenBeanDefinitionNames = null; } if (existingDefinition != null || containsSingleton(beanName)) { resetBeanDefinition(beanName); } else if (isConfigurationFrozen()) { clearByTypeCache(); } }
第三步发布注册事件。
2.ApplicationContext应用场景
ApplicationContext 在 BeanFactory 的基础上扩展了以下几点：
(1) 支持不同的信息源。 扩展了MessageSource接口，扩展的功能可以指出国际化。
(2) 访问资源。继承了ResourcePatternResolver。这样我们可以从不同的地方获取Bean定义信息。
(3) 支持应用事件。继承了ApplicationEventPublisher接口，从而在上下文中引入了事件机制。这些事件和Bean的生命周期的结合为Bean管理提供了遍历。
以 AnnotationConfigApplicationContext 为例子说明其简单的注册过程。
编程式的过程如下：
AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(MainApp.class); UserService bean = applicationContext.getBean(UserService.class); String s = bean.method1(); System.out.println(s);
其实只要第一行代码就已经完成了IoC的创建。
简答分析下其过程：
1》AnnotationConfigApplicationContext 构造方法中也是先创建了一个Reader、一个Scanner。接着调用自身的register 方法、refresh方法
private final AnnotatedBeanDefinitionReader reader; private final ClassPathBeanDefinitionScanner scanner; /** * Create a new AnnotationConfigApplicationContext, deriving bean definitions * from the given component classes and automatically refreshing the context. * @param componentClasses one or more component classes — for example, * {@link Configuration @Configuration} classes */ public AnnotationConfigApplicationContext(Class<?>... componentClasses) { this(); register(componentClasses); refresh(); } /** * Create a new AnnotationConfigApplicationContext that needs to be populated * through {@link #register} calls and then manually {@linkplain #refresh refreshed}. */ public AnnotationConfigApplicationContext() { this.reader = new AnnotatedBeanDefinitionReader(this); this.scanner = new ClassPathBeanDefinitionScanner(this); }
2》org.springframework.context.annotation.AnnotationConfigApplicationContext#register 方法如下： 其实也是调用reader将自身注册进去
@Override public void register(Class<?>... componentClasses) { Assert.notEmpty(componentClasses, "At least one component class must be specified"); this.reader.register(componentClasses); }
2.1》org.springframework.context.annotation.AnnotatedBeanDefinitionReader#register 代码如下： 最终也是到 doRegisterBean 方法
/** * Register one or more component classes to be processed. * <p>Calls to {@code register} are idempotent; adding the same * component class more than once has no additional effect. * @param componentClasses one or more component classes, * e.g. {@link Configuration @Configuration} classes */ public void register(Class<?>... componentClasses) { for (Class<?> componentClass : componentClasses) { registerBean(componentClass); } } /** * Register a bean from the given bean class, deriving its metadata from * class-declared annotations. * @param beanClass the class of the bean */ public void registerBean(Class<?> beanClass) { doRegisterBean(beanClass, null, null, null); } /** * Register a bean from the given bean class, deriving its metadata from * class-declared annotations. * @param beanClass the class of the bean * @param instanceSupplier a callback for creating an instance of the bean * (may be {@code null}) * @param name an explicit name for the bean * @param qualifiers specific qualifier annotations to consider, if any, * in addition to qualifiers at the bean class level * @param definitionCustomizers one or more callbacks for customizing the * factory's {@link BeanDefinition}, e.g. setting a lazy-init or primary flag * @since 5.0 */ <T> void doRegisterBean(Class<T> beanClass, @Nullable Supplier<T> instanceSupplier, @Nullable String name, @Nullable Class<? extends Annotation>[] qualifiers, BeanDefinitionCustomizer... definitionCustomizers) { AnnotatedGenericBeanDefinition abd = new AnnotatedGenericBeanDefinition(beanClass); if (this.conditionEvaluator.shouldSkip(abd.getMetadata())) { return; } abd.setInstanceSupplier(instanceSupplier); ScopeMetadata scopeMetadata = this.scopeMetadataResolver.resolveScopeMetadata(abd); abd.setScope(scopeMetadata.getScopeName()); String beanName = (name != null ? name : this.beanNameGenerator.generateBeanName(abd, this.registry)); AnnotationConfigUtils.processCommonDefinitionAnnotations(abd); if (qualifiers != null) { for (Class<? extends Annotation> qualifier : qualifiers) { if (Primary.class == qualifier) { abd.setPrimary(true); } else if (Lazy.class == qualifier) { abd.setLazyInit(true); } else { abd.addQualifier(new AutowireCandidateQualifier(qualifier)); } } } for (BeanDefinitionCustomizer customizer : definitionCustomizers) { customizer.customize(abd); } BeanDefinitionHolder definitionHolder = new BeanDefinitionHolder(abd, beanName); definitionHolder = AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry); BeanDefinitionReaderUtils.registerBeanDefinition(definitionHolder, this.registry); }
doRegisterBean 方法的核心是
2.1.1》new AnnotatedGenericBeanDefinition(beanClass); 建一个AnnotatedGenericBeanDefinition 对象，AnnotatedGenericBeanDefinition 构造方法内部读取了类的一些注解信息并封装到metadata属性中，其实就是一个BeanDefinition对象。之后设置一些数据，生成beanName。
2.2.2》AnnotationConfigUtils.processCommonDefinitionAnnotations(abd) 处理类上的注解信息，如下： 主要是处理类上的一些注解然后记录到上面生成的AnnotatedGenericBeanDefinition 对象中
public static void processCommonDefinitionAnnotations(AnnotatedBeanDefinition abd) { processCommonDefinitionAnnotations(abd, abd.getMetadata()); } static void processCommonDefinitionAnnotations(AnnotatedBeanDefinition abd, AnnotatedTypeMetadata metadata) { AnnotationAttributes lazy = attributesFor(metadata, Lazy.class); if (lazy != null) { abd.setLazyInit(lazy.getBoolean("value")); } else if (abd.getMetadata() != metadata) { lazy = attributesFor(abd.getMetadata(), Lazy.class); if (lazy != null) { abd.setLazyInit(lazy.getBoolean("value")); } } if (metadata.isAnnotated(Primary.class.getName())) { abd.setPrimary(true); } AnnotationAttributes dependsOn = attributesFor(metadata, DependsOn.class); if (dependsOn != null) { abd.setDependsOn(dependsOn.getStringArray("value")); } AnnotationAttributes role = attributesFor(metadata, Role.class); if (role != null) { abd.setRole(role.getNumber("value").intValue()); } AnnotationAttributes description = attributesFor(metadata, Description.class); if (description != null) { abd.setDescription(description.getString("value")); } }
2.2.3》接下来就同上面XmlBeanFactory逻辑一样：创建BeanDefinitionHolder 对象
2.2.4》AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry) 主要是判断类的@Scope的proxyMode 的属性，如果不是DEFAULT、NO 会根据设置生成对应的代理对象，也就是说改变 definitionHolder 的引用。org.springframework.context.annotation.Scope 的proxyMode 可以指定为IoC容器是否生成代理对象，如果生成代理对象，会在下面注册BeanDefnition时注册两个对象，一个源对象、一个代理对象。org.springframework.context.annotation.AnnotationConfigUtils#applyScopedProxyMode 源码如下：
static BeanDefinitionHolder applyScopedProxyMode( ScopeMetadata metadata, BeanDefinitionHolder definition, BeanDefinitionRegistry registry) { ScopedProxyMode scopedProxyMode = metadata.getScopedProxyMode(); if (scopedProxyMode.equals(ScopedProxyMode.NO)) { return definition; } boolean proxyTargetClass = scopedProxyMode.equals(ScopedProxyMode.TARGET_CLASS); return ScopedProxyCreator.createScopedProxy(definition, registry, proxyTargetClass); }
2.2.4.1》如果不是NO的话会生成Proxy，org.springframework.context.annotation.ScopedProxyCreator#createScopedProxy 源码如下：
public static BeanDefinitionHolder createScopedProxy( BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry, boolean proxyTargetClass) { return ScopedProxyUtils.createScopedProxy(definitionHolder, registry, proxyTargetClass); }
2.2.4.2》org.springframework.aop.scope.ScopedProxyUtils#createScopedProxy源码如下：
/** * Generate a scoped proxy for the supplied target bean, registering the target * bean with an internal name and setting 'targetBeanName' on the scoped proxy. * @param definition the original bean definition * @param registry the bean definition registry * @param proxyTargetClass whether to create a target class proxy * @return the scoped proxy definition * @see #getTargetBeanName(String) * @see #getOriginalBeanName(String) */ public static BeanDefinitionHolder createScopedProxy(BeanDefinitionHolder definition, BeanDefinitionRegistry registry, boolean proxyTargetClass) { String originalBeanName = definition.getBeanName(); BeanDefinition targetDefinition = definition.getBeanDefinition(); String targetBeanName = getTargetBeanName(originalBeanName); // Create a scoped proxy definition for the original bean name, // "hiding" the target bean in an internal target definition. RootBeanDefinition proxyDefinition = new RootBeanDefinition(ScopedProxyFactoryBean.class); proxyDefinition.setDecoratedDefinition(new BeanDefinitionHolder(targetDefinition, targetBeanName)); proxyDefinition.setOriginatingBeanDefinition(targetDefinition); proxyDefinition.setSource(definition.getSource()); proxyDefinition.setRole(targetDefinition.getRole()); proxyDefinition.getPropertyValues().add("targetBeanName", targetBeanName); if (proxyTargetClass) { targetDefinition.setAttribute(AutoProxyUtils.PRESERVE_TARGET_CLASS_ATTRIBUTE, Boolean.TRUE); // ScopedProxyFactoryBean's "proxyTargetClass" default is TRUE, so we don't need to set it explicitly here. } else { proxyDefinition.getPropertyValues().add("proxyTargetClass", Boolean.FALSE); } // Copy autowire settings from original bean definition. proxyDefinition.setAutowireCandidate(targetDefinition.isAutowireCandidate()); proxyDefinition.setPrimary(targetDefinition.isPrimary()); if (targetDefinition instanceof AbstractBeanDefinition) { proxyDefinition.copyQualifiersFrom((AbstractBeanDefinition) targetDefinition); } // The target bean should be ignored in favor of the scoped proxy. targetDefinition.setAutowireCandidate(false); targetDefinition.setPrimary(false); // Register the target bean as separate bean in the factory. registry.registerBeanDefinition(targetBeanName, targetDefinition); // Return the scoped proxy definition as primary bean definition // (potentially an inner bean). return new BeanDefinitionHolder(proxyDefinition, originalBeanName, definition.getAliases()); }
这里的逻辑大致是：
(1)根据源beanName生成targetName的规则如下：
private static final String TARGET_NAME_PREFIX = "scopedTarget."; public static String getTargetBeanName(String originalBeanName) { return TARGET_NAME_PREFIX + originalBeanName; }
(2) 接下来就是创建一个RootBeanDefinition 对象，并且记录原来的BeanDefinition信息以及代理Definition信息
RootBeanDefinition proxyDefinition = new RootBeanDefinition(ScopedProxyFactoryBean.class);
这行代码主要是将BeanDefinition的class设置为ScopedProxyFactoryBean， ScopedProxyFactoryBean 是一个FactoryBean，是一个生产Bean的工厂。可以猜出来是一个生产代理对象的工厂。源码如下：
/* * Copyright 2002-2018 the original author or authors. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * https://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package org.springframework.aop.scope; import java.lang.reflect.Modifier; import org.springframework.aop.framework.AopInfrastructureBean; import org.springframework.aop.framework.ProxyConfig; import org.springframework.aop.framework.ProxyFactory; import org.springframework.aop.support.DelegatingIntroductionInterceptor; import org.springframework.aop.target.SimpleBeanTargetSource; import org.springframework.beans.factory.BeanFactory; import org.springframework.beans.factory.BeanFactoryAware; import org.springframework.beans.factory.FactoryBean; import org.springframework.beans.factory.FactoryBeanNotInitializedException; import org.springframework.beans.factory.config.ConfigurableBeanFactory; import org.springframework.lang.Nullable; import org.springframework.util.Assert; import org.springframework.util.ClassUtils; /** * Convenient proxy factory bean for scoped objects. * * <p>Proxies created using this factory bean are thread-safe singletons * and may be injected into shared objects, with transparent scoping behavior. * * <p>Proxies returned by this class implement the {@link ScopedObject} interface. * This presently allows for removing the corresponding object from the scope, * seamlessly creating a new instance in the scope on next access. * * <p>Please note that the proxies created by this factory are * <i>class-based</i> proxies by default. This can be customized * through switching the "proxyTargetClass" property to "false". * * @author Rod Johnson * @author Juergen Hoeller * @since 2.0 * @see #setProxyTargetClass */ @SuppressWarnings("serial") public class ScopedProxyFactoryBean extends ProxyConfig implements FactoryBean<Object>, BeanFactoryAware, AopInfrastructureBean { /** The TargetSource that manages scoping. */ private final SimpleBeanTargetSource scopedTargetSource = new SimpleBeanTargetSource(); /** The name of the target bean. */ @Nullable private String targetBeanName; /** The cached singleton proxy. */ @Nullable private Object proxy; /** * Create a new ScopedProxyFactoryBean instance. */ public ScopedProxyFactoryBean() { setProxyTargetClass(true); } /** * Set the name of the bean that is to be scoped. */ public void setTargetBeanName(String targetBeanName) { this.targetBeanName = targetBeanName; this.scopedTargetSource.setTargetBeanName(targetBeanName); } @Override public void setBeanFactory(BeanFactory beanFactory) { if (!(beanFactory instanceof ConfigurableBeanFactory)) { throw new IllegalStateException("Not running in a ConfigurableBeanFactory: " + beanFactory); } ConfigurableBeanFactory cbf = (ConfigurableBeanFactory) beanFactory; this.scopedTargetSource.setBeanFactory(beanFactory); ProxyFactory pf = new ProxyFactory(); pf.copyFrom(this); pf.setTargetSource(this.scopedTargetSource); Assert.notNull(this.targetBeanName, "Property 'targetBeanName' is required"); Class<?> beanType = beanFactory.getType(this.targetBeanName); if (beanType == null) { throw new IllegalStateException("Cannot create scoped proxy for bean '" + this.targetBeanName + "': Target type could not be determined at the time of proxy creation."); } if (!isProxyTargetClass() || beanType.isInterface() || Modifier.isPrivate(beanType.getModifiers())) { pf.setInterfaces(ClassUtils.getAllInterfacesForClass(beanType, cbf.getBeanClassLoader())); } // Add an introduction that implements only the methods on ScopedObject. ScopedObject scopedObject = new DefaultScopedObject(cbf, this.scopedTargetSource.getTargetBeanName()); pf.addAdvice(new DelegatingIntroductionInterceptor(scopedObject)); // Add the AopInfrastructureBean marker to indicate that the scoped proxy // itself is not subject to auto-proxying! Only its target bean is. pf.addInterface(AopInfrastructureBean.class); this.proxy = pf.getProxy(cbf.getBeanClassLoader()); } @Override public Object getObject() { if (this.proxy == null) { throw new FactoryBeanNotInitializedException(); } return this.proxy; } @Override public Class<?> getObjectType() { if (this.proxy != null) { return this.proxy.getClass(); } return this.scopedTargetSource.getTargetClass(); } @Override public boolean isSingleton() { return true; } }
(3) 下面代码
// Copy autowire settings from original bean definition. proxyDefinition.setAutowireCandidate(targetDefinition.isAutowireCandidate()); proxyDefinition.setPrimary(targetDefinition.isPrimary()); if (targetDefinition instanceof AbstractBeanDefinition) { proxyDefinition.copyQualifiersFrom((AbstractBeanDefinition) targetDefinition); } // The target bean should be ignored in favor of the scoped proxy. targetDefinition.setAutowireCandidate(false); targetDefinition.setPrimary(false);
将autowireCandidate 属性和Primary 属性置为目标definition的属性，然后将目标beanDefinition的autowireCandidate 属性和Primary属性置为false。
autowireCandidate 为false，容器在查找自动装配对象时，将不考虑该bean，即该bean不会被作为其它bean自动装配的候选者，但该bean本身还是可以使用自动装配来注入其它bean的。
Primary 属性很好理解，是否作为主对象。也就是如果默认会切换代理对象为Primary对象，原来的对象Primary为false。
(4)下面代码注册目标对象，beanName为 "scopedTarget." + 原来的BeanName
// Register the target bean as separate bean in the factory. registry.registerBeanDefinition(targetBeanName, targetDefinition);
(5) 然后返回代理BeanDefinition，beanName为原来的BeanName。
return new BeanDefinitionHolder(proxyDefinition, originalBeanName, definition.getAliases())
(6) 也就是用原来默认的beanName获取到的是代理对象，用"scopeTarget."+默认beanName 获取的是目标对象。如果目标对象是Primary主对象，代理对象会代替其成为Primary对象。
2.2.3 》最后调用如下方法注册Bean， registry 就是创建的AnnotationConfigApplicationContext 对象
BeanDefinitionReaderUtils.registerBeanDefinition(definitionHolder, this.registry);
2.2.3.1》org.springframework.beans.factory.support.BeanDefinitionReaderUtils#registerBeanDefinition 方法同上，调用具体的工厂注册Bean和别名
/** * Register the given bean definition with the given bean factory. * @param definitionHolder the bean definition including name and aliases * @param registry the bean factory to register with * @throws BeanDefinitionStoreException if registration failed */ public static void registerBeanDefinition( BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry) throws BeanDefinitionStoreException { // Register bean definition under primary name. String beanName = definitionHolder.getBeanName(); registry.registerBeanDefinition(beanName, definitionHolder.getBeanDefinition()); // Register aliases for bean name, if any. String[] aliases = definitionHolder.getAliases(); if (aliases != null) { for (String alias : aliases) { registry.registerAlias(beanName, alias); } } }
2.2.3.2》最终会交给org.springframework.beans.factory.support.DefaultListableBeanFactory#registerBeanDefinition 方法来注册Bean
@Override public void registerBeanDefinition(String beanName, BeanDefinition beanDefinition) throws BeanDefinitionStoreException { Assert.hasText(beanName, "Bean name must not be empty"); Assert.notNull(beanDefinition, "BeanDefinition must not be null"); if (beanDefinition instanceof AbstractBeanDefinition) { try { ((AbstractBeanDefinition) beanDefinition).validate(); } catch (BeanDefinitionValidationException ex) { throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName, "Validation of bean definition failed", ex); } } BeanDefinition existingDefinition = this.beanDefinitionMap.get(beanName); if (existingDefinition != null) { if (!isAllowBeanDefinitionOverriding()) { throw new BeanDefinitionOverrideException(beanName, beanDefinition, existingDefinition); } else if (existingDefinition.getRole() < beanDefinition.getRole()) { // e.g. was ROLE_APPLICATION, now overriding with ROLE_SUPPORT or ROLE_INFRASTRUCTURE if (logger.isInfoEnabled()) { logger.info("Overriding user-defined bean definition for bean '" + beanName + "' with a framework-generated bean definition: replacing [" + existingDefinition + "] with [" + beanDefinition + "]"); } } else if (!beanDefinition.equals(existingDefinition)) { if (logger.isDebugEnabled()) { logger.debug("Overriding bean definition for bean '" + beanName + "' with a different definition: replacing [" + existingDefinition + "] with [" + beanDefinition + "]"); } } else { if (logger.isTraceEnabled()) { logger.trace("Overriding bean definition for bean '" + beanName + "' with an equivalent definition: replacing [" + existingDefinition + "] with [" + beanDefinition + "]"); } } this.beanDefinitionMap.put(beanName, beanDefinition); } else { if (hasBeanCreationStarted()) { // Cannot modify startup-time collection elements anymore (for stable iteration) synchronized (this.beanDefinitionMap) { this.beanDefinitionMap.put(beanName, beanDefinition); List<String> updatedDefinitions = new ArrayList<>(this.beanDefinitionNames.size() + 1); updatedDefinitions.addAll(this.beanDefinitionNames); updatedDefinitions.add(beanName); this.beanDefinitionNames = updatedDefinitions; removeManualSingletonName(beanName); } } else { // Still in startup registration phase this.beanDefinitionMap.put(beanName, beanDefinition); this.beanDefinitionNames.add(beanName); removeManualSingletonName(beanName); } this.frozenBeanDefinitionNames = null; } if (existingDefinition != null || containsSingleton(beanName)) { resetBeanDefinition(beanName); } else if (isConfigurationFrozen()) { clearByTypeCache(); } }
3》 上面将主类注入到了IoC中，接下来就是 refresh(); 方法注入其他业务Bean。 接下来这个才是IoC的核心入口，标记着IoC容器创建的开始。具体来说，启动包括BeanDefinition的Resource定位(BeanDefinition的定位)、载入(将Bean封装成BeanDefinition以及BeanDefinitionHolder)、注册(将BeanDefinition注入到一个ConcurrentHashMap)三个基本过程。分别对应BeanDefinitionReader、BeanDefinitionLoader、BeanDefinitionRegistry。
注意这里的过程只是IoC容器的初始化，不包含Bean依赖注入的实现。在SpringIoC的设计中，Bean定义的载入和依赖注入是两个独立的过程。依赖注入一般发生在应用第一次通过getBean向容器索要Bean的时候。这里设计到Lazy 注解的使用。一般情况下，Spring容器在启动时会创建所有的Bean对象，使用@Lazy注解可以将Bean对象的创建延迟到第一次使用Bean的时候。@Lazy也可以解决许多循环依赖的问题。
org.springframework.context.support.AbstractApplicationContext#refresh 源码如下：
@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(); // 装备BeanFactory以及环境信息. prepareBeanFactory(beanFactory); try { // 设置Bean的后置处理. postProcessBeanFactory(beanFactory); // 调用BeanFactory的后处理器. 这些后处理器是在Bean定义中向容器注册的 invokeBeanFactoryPostProcessors(beanFactory); // 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. 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(); // 实例化所有的(non-lazy-init)单件==也就是创建Bean的操作是在这一步进行的 finishBeanFactoryInitialization(beanFactory); // 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(); } } }
3.1》prepareRefresh 这个方法没什么，就是简单的记录了开始时间以及准备前提环境
3.2》obtainFreshBeanFactory(); 判断是否有工厂
/** * Tell the subclass to refresh the internal bean factory. * @return the fresh BeanFactory instance * @see #refreshBeanFactory() * @see #getBeanFactory() */ protected ConfigurableListableBeanFactory obtainFreshBeanFactory() { refreshBeanFactory(); return getBeanFactory(); }
3.2.1》 refreshBeanFactory方法是继承下来的org.springframework.context.support.GenericApplicationContext#refreshBeanFactory
3.3》 prepareBeanFactory(beanFactory); 是提前处理BeanFactory的环境信息等
3.4》invokeBeanFactoryPostProcessors 是核心所在，这里是调用BeanFactory的后处理器。是在注入之后，实例化之前调用，因此可以用于动态的注入BeanDefinition信息。是从父类AbstractApplicationContext继承下来的一个方法，org.springframework.context.support.AbstractApplicationContext#invokeBeanFactoryPostProcessors：
/** * Instantiate and invoke all registered BeanFactoryPostProcessor beans, * respecting explicit order if given. * <p>Must be called before singleton instantiation. */ 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 (beanFactory.getTempClassLoader() == null && beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) { beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory)); beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader())); } }
3.4.1 org.springframework.context.support.PostProcessorRegistrationDelegate#invokeBeanFactoryPostProcessors方法如下：
public static void invokeBeanFactoryPostProcessors( ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) { // 保存所有后置处理器bean名称的集合 Set<String> processedBeans = new HashSet<>(); // 判断beanFactory 是否是BeanDefinitionRegistry // 当是BeanDefinitionRegistry 时 将beanFactoryPostProcessors 分为BeanFactoryPostProcessor集合与BeanDefinitionRegistryPostProcessor集合 if (beanFactory instanceof BeanDefinitionRegistry) { BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory; List<BeanFactoryPostProcessor> regularPostProcessors = new ArrayList<>(); List<BeanDefinitionRegistryPostProcessor> registryProcessors = new ArrayList<>(); for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) { if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) { BeanDefinitionRegistryPostProcessor registryProcessor = (BeanDefinitionRegistryPostProcessor) postProcessor; // 当前postProcessor为BeanDefinitionRegistryPostProcessor时执行postProcessBeanDefinitionRegistry方法 registryProcessor.postProcessBeanDefinitionRegistry(registry); registryProcessors.add(registryProcessor); } else { regularPostProcessors.add(postProcessor); } } // Do not initialize FactoryBeans here: We need to leave all regular beans // uninitialized to let the bean factory post-processors apply to them! // Separate between BeanDefinitionRegistryPostProcessors that implement // PriorityOrdered, Ordered, and the rest. List<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors = new ArrayList<>(); // 首先在容器中查找实现了PriorityOrdered接口的的BeanDefinitionRegistryPostProcessors（bean定义注册后置处理器）名称 // 将查找到的名称集合放置到processedBeans中，以及将后置处理器添加到集合currentRegistryProcessors中 // First, invoke the BeanDefinitionRegistryPostProcessors that implement PriorityOrdered. String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false); for (String ppName : postProcessorNames) { if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) { currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class)); processedBeans.add(ppName); } } sortPostProcessors(currentRegistryProcessors, beanFactory); registryProcessors.addAll(currentRegistryProcessors); // 遍历循环执行currentRegistryProcessors集合中的bean定义注册后置处理器 invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry); // 清空currentRegistryProcessors集合 currentRegistryProcessors.clear(); // Next, invoke the BeanDefinitionRegistryPostProcessors that implement Ordered. postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false); for (String ppName : postProcessorNames) { if (!processedBeans.contains(ppName) && beanFactory.isTypeMatch(ppName, Ordered.class)) { currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class)); processedBeans.add(ppName); } } sortPostProcessors(currentRegistryProcessors, beanFactory); registryProcessors.addAll(currentRegistryProcessors); invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry); currentRegistryProcessors.clear(); // Finally, invoke all other BeanDefinitionRegistryPostProcessors until no further ones appear. boolean reiterate = true; while (reiterate) { reiterate = false; postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false); for (String ppName : postProcessorNames) { if (!processedBeans.contains(ppName)) { currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class)); processedBeans.add(ppName); reiterate = true; } } sortPostProcessors(currentRegistryProcessors, beanFactory); registryProcessors.addAll(currentRegistryProcessors); invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry); currentRegistryProcessors.clear(); } // Now, invoke the postProcessBeanFactory callback of all processors handled so far. invokeBeanFactoryPostProcessors(registryProcessors, beanFactory); invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory); } else { // Invoke factory processors registered with the context instance. invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory); } // Do not initialize FactoryBeans here: We need to leave all regular beans // uninitialized to let the bean factory post-processors apply to them! String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false); // Separate between BeanFactoryPostProcessors that implement PriorityOrdered, // Ordered, and the rest. List<BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList<>(); List<String> orderedPostProcessorNames = new ArrayList<>(); List<String> nonOrderedPostProcessorNames = new ArrayList<>(); for (String ppName : postProcessorNames) { if (processedBeans.contains(ppName)) { // skip - already processed in first phase above } else if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) { priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class)); } else if (beanFactory.isTypeMatch(ppName, Ordered.class)) { orderedPostProcessorNames.add(ppName); } else { nonOrderedPostProcessorNames.add(ppName); } } // First, invoke the BeanFactoryPostProcessors that implement PriorityOrdered. sortPostProcessors(priorityOrderedPostProcessors, beanFactory); invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory); // Next, invoke the BeanFactoryPostProcessors that implement Ordered. List<BeanFactoryPostProcessor> orderedPostProcessors = new ArrayList<>(); for (String postProcessorName : orderedPostProcessorNames) { orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class)); } sortPostProcessors(orderedPostProcessors, beanFactory); invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory); // Finally, invoke all other BeanFactoryPostProcessors. List<BeanFactoryPostProcessor> nonOrderedPostProcessors = new ArrayList<>(); for (String postProcessorName : nonOrderedPostProcessorNames) { nonOrderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class)); } invokeBeanFactoryPostProcessors(nonOrderedPostProcessors, beanFactory); // Clear cached merged bean definitions since the post-processors might have // modified the original metadata, e.g. replacing placeholders in values... beanFactory.clearMetadataCache(); }
根据传入beanFactory类型可分为两部分：我们着重看beanFactory是BeanDefinitionRegistry类型时的流程
1. 遍历传入后置处理器集合查找类型为BeanDefinitionRegistryPostProcessor的后置处理器，调用后置处理器的postProcessBeanDefinitionRegistry方法
2. 在容器中查找所有的实现了PriorityOrdered接口的BeanDefinitionRegistryPostProcessor集合，对后置处理器集合排序，遍历，执行后置处理的postProcessBeanDefinitionRegistry方法
/** * Invoke the given BeanDefinitionRegistryPostProcessor beans. */ private static void invokeBeanDefinitionRegistryPostProcessors( Collection<? extends BeanDefinitionRegistryPostProcessor> postProcessors, BeanDefinitionRegistry registry) { for (BeanDefinitionRegistryPostProcessor postProcessor : postProcessors) { postProcessor.postProcessBeanDefinitionRegistry(registry); } }
3.在容器中查找所有实现了Ordered接口的BeanDefinitionRegistryPostProcessor集合，对后置处理器集合排序，遍历，执行后置处理的postProcessBeanDefinitionRegistry方法。
4.在容器中查找其它（未实现排序接口）的BeanDefinitionRegistryPostProcessor并添加到集合nonOrderedPostProcessors中，对后置处理器集合排序，遍历，执行后置处理的postProcessBeanDefinitionRegistry方法
5.当前所有的BeanDefinitionRegistryPostProcessor处理器的方法postProcessBeanDefinitionRegistry 执行完毕后，执行其父类postProcessBeanFactory方法
6. 执行所有非BeanDefinitionRegistryPostProcessor类型的后置处理器的postProcessBeanFactory方法
3.4.2》 上面会获取到org.springframework.context.annotation.ConfigurationClassPostProcessor 并添加到currentRegistryProcessors ， 然后调用invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
/** * Invoke the given BeanDefinitionRegistryPostProcessor beans. */ private static void invokeBeanDefinitionRegistryPostProcessors( Collection<? extends BeanDefinitionRegistryPostProcessor> postProcessors, BeanDefinitionRegistry registry) { for (BeanDefinitionRegistryPostProcessor postProcessor : postProcessors) { postProcessor.postProcessBeanDefinitionRegistry(registry); } }
3.4.3》 接下来就是调用org.springframework.context.annotation.ConfigurationClassPostProcessor#postProcessBeanDefinitionRegistry
/** * Derive further bean definitions from the configuration classes in the registry. */ @Override public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) { int registryId = System.identityHashCode(registry); if (this.registriesPostProcessed.contains(registryId)) { throw new IllegalStateException( "postProcessBeanDefinitionRegistry already called on this post-processor against " + registry); } if (this.factoriesPostProcessed.contains(registryId)) { throw new IllegalStateException( "postProcessBeanFactory already called on this post-processor against " + registry); } this.registriesPostProcessed.add(registryId); processConfigBeanDefinitions(registry); }
3.4.4》org.springframework.context.annotation.ConfigurationClassPostProcessor#processConfigBeanDefinitions 方法如下：
/** * Build and validate a configuration model based on the registry of * {@link Configuration} classes. */ public void processConfigBeanDefinitions(BeanDefinitionRegistry registry) { List<BeanDefinitionHolder> configCandidates = new ArrayList<>(); String[] candidateNames = registry.getBeanDefinitionNames(); for (String beanName : candidateNames) { BeanDefinition beanDef = registry.getBeanDefinition(beanName); if (ConfigurationClassUtils.isFullConfigurationClass(beanDef) || ConfigurationClassUtils.isLiteConfigurationClass(beanDef)) { if (logger.isDebugEnabled()) { logger.debug("Bean definition has already been processed as a configuration class: " + beanDef); } } else if (ConfigurationClassUtils.checkConfigurationClassCandidate(beanDef, this.metadataReaderFactory)) { configCandidates.add(new BeanDefinitionHolder(beanDef, beanName)); } } // Return immediately if no @Configuration classes were found if (configCandidates.isEmpty()) { return; } // Sort by previously determined @Order value, if applicable configCandidates.sort((bd1, bd2) -> { int i1 = ConfigurationClassUtils.getOrder(bd1.getBeanDefinition()); int i2 = ConfigurationClassUtils.getOrder(bd2.getBeanDefinition()); return Integer.compare(i1, i2); }); // Detect any custom bean name generation strategy supplied through the enclosing application context SingletonBeanRegistry sbr = null; if (registry instanceof SingletonBeanRegistry) { sbr = (SingletonBeanRegistry) registry; if (!this.localBeanNameGeneratorSet) { BeanNameGenerator generator = (BeanNameGenerator) sbr.getSingleton(CONFIGURATION_BEAN_NAME_GENERATOR); if (generator != null) { this.componentScanBeanNameGenerator = generator; this.importBeanNameGenerator = generator; } } } if (this.environment == null) { this.environment = new StandardEnvironment(); } // Parse each @Configuration class ConfigurationClassParser parser = new ConfigurationClassParser( this.metadataReaderFactory, this.problemReporter, this.environment, this.resourceLoader, this.componentScanBeanNameGenerator, registry); Set<BeanDefinitionHolder> candidates = new LinkedHashSet<>(configCandidates); Set<ConfigurationClass> alreadyParsed = new HashSet<>(configCandidates.size()); do { parser.parse(candidates); parser.validate(); Set<ConfigurationClass> configClasses = new LinkedHashSet<>(parser.getConfigurationClasses()); configClasses.removeAll(alreadyParsed); // Read the model and create bean definitions based on its content if (this.reader == null) { this.reader = new ConfigurationClassBeanDefinitionReader( registry, this.sourceExtractor, this.resourceLoader, this.environment, this.importBeanNameGenerator, parser.getImportRegistry()); } this.reader.loadBeanDefinitions(configClasses); alreadyParsed.addAll(configClasses); candidates.clear(); if (registry.getBeanDefinitionCount() > candidateNames.length) { String[] newCandidateNames = registry.getBeanDefinitionNames(); Set<String> oldCandidateNames = new HashSet<>(Arrays.asList(candidateNames)); Set<String> alreadyParsedClasses = new HashSet<>(); for (ConfigurationClass configurationClass : alreadyParsed) { alreadyParsedClasses.add(configurationClass.getMetadata().getClassName()); } for (String candidateName : newCandidateNames) { if (!oldCandidateNames.contains(candidateName)) { BeanDefinition bd = registry.getBeanDefinition(candidateName); if (ConfigurationClassUtils.checkConfigurationClassCandidate(bd, this.metadataReaderFactory) && !alreadyParsedClasses.contains(bd.getBeanClassName())) { candidates.add(new BeanDefinitionHolder(bd, candidateName)); } } } candidateNames = newCandidateNames; } } while (!candidates.isEmpty()); // Register the ImportRegistry as a bean in order to support ImportAware @Configuration classes if (sbr != null && !sbr.containsSingleton(IMPORT_REGISTRY_BEAN_NAME)) { sbr.registerSingleton(IMPORT_REGISTRY_BEAN_NAME, parser.getImportRegistry()); } if (this.metadataReaderFactory instanceof CachingMetadataReaderFactory) { // Clear cache in externally provided MetadataReaderFactory; this is a no-op // for a shared cache since it'll be cleared by the ApplicationContext. ((CachingMetadataReaderFactory) this.metadataReaderFactory).clearCache(); } }
(1) 这里的重点是先判断是否是包含配置类。 ConfigurationClassUtils.checkConfigurationClassCandidate(beanDef, this.metadataReaderFactory) 方法。 其中可以作为配置的注解包括：
candidateIndicators.add(Component.class.getName()); candidateIndicators.add(ComponentScan.class.getName()); candidateIndicators.add(Import.class.getName()); candidateIndicators.add(ImportResource.class.getName());
我们在主类打了@ComponentScan 注解，所以会被处理。 这里也了解到为什么@SpringBootApplication 注解加了@ComponentScan 注解。 而且@ComponentScan 注解可以指定许多属性，重要的包括是否Lazy，scopedProxy 上面是否使用代理等信息。
(2) 第二步就是创建一个name生成器，然后创建一个 ConfigurationClassParser， 从名字就可以看出来是解析配置用的。然后调用parser.parse(candidates); 解析出信息存入ConfigurationClass。这个里面有几个重要的方法：org.springframework.context.annotation.ConfigurationClassParser#parse(java.util.Set<org.springframework.beans.factory.config.BeanDefinitionHolder>)
public void parse(Set<BeanDefinitionHolder> configCandidates) { for (BeanDefinitionHolder holder : configCandidates) { BeanDefinition bd = holder.getBeanDefinition(); try { if (bd instanceof AnnotatedBeanDefinition) { parse(((AnnotatedBeanDefinition) bd).getMetadata(), holder.getBeanName()); } else if (bd instanceof AbstractBeanDefinition && ((AbstractBeanDefinition) bd).hasBeanClass()) { parse(((AbstractBeanDefinition) bd).getBeanClass(), holder.getBeanName()); } else { parse(bd.getBeanClassName(), holder.getBeanName()); } } catch (BeanDefinitionStoreException ex) { throw ex; } catch (Throwable ex) { throw new BeanDefinitionStoreException( "Failed to parse configuration class [" + bd.getBeanClassName() + "]", ex); } } this.deferredImportSelectorHandler.process(); }
注解扫描走的是org.springframework.context.annotation.ConfigurationClassParser#parse(org.springframework.core.type.AnnotationMetadata, java.lang.String)
protected final void parse(AnnotationMetadata metadata, String beanName) throws IOException { processConfigurationClass(new ConfigurationClass(metadata, beanName)); }
接着调用下面方法
protected void processConfigurationClass(ConfigurationClass configClass) throws IOException { if (this.conditionEvaluator.shouldSkip(configClass.getMetadata(), ConfigurationPhase.PARSE_CONFIGURATION)) { return; } ConfigurationClass existingClass = this.configurationClasses.get(configClass); if (existingClass != null) { if (configClass.isImported()) { if (existingClass.isImported()) { existingClass.mergeImportedBy(configClass); } // Otherwise ignore new imported config class; existing non-imported class overrides it. return; } else { // Explicit bean definition found, probably replacing an import. // Let's remove the old one and go with the new one. this.configurationClasses.remove(configClass); this.knownSuperclasses.values().removeIf(configClass::equals); } } // Recursively process the configuration class and its superclass hierarchy. SourceClass sourceClass = asSourceClass(configClass); do { sourceClass = doProcessConfigurationClass(configClass, sourceClass); } while (sourceClass != null); this.configurationClasses.put(configClass, configClass); }
接着就是核心的扫描以及维护信息
protected final SourceClass doProcessConfigurationClass(ConfigurationClass configClass, SourceClass sourceClass) throws IOException { if (configClass.getMetadata().isAnnotated(Component.class.getName())) { // Recursively process any member (nested) classes first processMemberClasses(configClass, sourceClass); } // Process any @PropertySource annotations for (AnnotationAttributes propertySource : AnnotationConfigUtils.attributesForRepeatable( sourceClass.getMetadata(), PropertySources.class, org.springframework.context.annotation.PropertySource.class)) { if (this.environment instanceof ConfigurableEnvironment) { processPropertySource(propertySource); } else { logger.info("Ignoring @PropertySource annotation on [" + sourceClass.getMetadata().getClassName() + "]. Reason: Environment must implement ConfigurableEnvironment"); } } // Process any @ComponentScan annotations 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 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(); } if (ConfigurationClassUtils.checkConfigurationClassCandidate(bdCand, this.metadataReaderFactory)) { parse(bdCand.getBeanClassName(), holder.getBeanName()); } } } } // Process any @Import annotations 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; }
这里会处理一些注解信息，包含@Import等信息，其中org.springframework.context.annotation.ComponentScanAnnotationParser#parse处理@ComponentScan注解，源码如下：
public Set<BeanDefinitionHolder> parse(AnnotationAttributes componentScan, final String declaringClass) { ClassPathBeanDefinitionScanner scanner = new ClassPathBeanDefinitionScanner(this.registry, componentScan.getBoolean("useDefaultFilters"), this.environment, this.resourceLoader); Class<? extends BeanNameGenerator> generatorClass = componentScan.getClass("nameGenerator"); boolean useInheritedGenerator = (BeanNameGenerator.class == generatorClass); scanner.setBeanNameGenerator(useInheritedGenerator ? this.beanNameGenerator : BeanUtils.instantiateClass(generatorClass)); ScopedProxyMode scopedProxyMode = componentScan.getEnum("scopedProxy"); if (scopedProxyMode != ScopedProxyMode.DEFAULT) { scanner.setScopedProxyMode(scopedProxyMode); } else { Class<? extends ScopeMetadataResolver> resolverClass = componentScan.getClass("scopeResolver"); scanner.setScopeMetadataResolver(BeanUtils.instantiateClass(resolverClass)); } scanner.setResourcePattern(componentScan.getString("resourcePattern")); for (AnnotationAttributes filter : componentScan.getAnnotationArray("includeFilters")) { for (TypeFilter typeFilter : typeFiltersFor(filter)) { scanner.addIncludeFilter(typeFilter); } } for (AnnotationAttributes filter : componentScan.getAnnotationArray("excludeFilters")) { for (TypeFilter typeFilter : typeFiltersFor(filter)) { scanner.addExcludeFilter(typeFilter); } } boolean lazyInit = componentScan.getBoolean("lazyInit"); if (lazyInit) { scanner.getBeanDefinitionDefaults().setLazyInit(true); } Set<String> basePackages = new LinkedHashSet<>(); String[] basePackagesArray = componentScan.getStringArray("basePackages"); for (String pkg : basePackagesArray) { String[] tokenized = StringUtils.tokenizeToStringArray(this.environment.resolvePlaceholders(pkg), ConfigurableApplicationContext.CONFIG_LOCATION_DELIMITERS); Collections.addAll(basePackages, tokenized); } for (Class<?> clazz : componentScan.getClassArray("basePackageClasses")) { basePackages.add(ClassUtils.getPackageName(clazz)); }
// 取不到值取当前配置类的包名为扫描的包 if (basePackages.isEmpty()) { basePackages.add(ClassUtils.getPackageName(declaringClass)); } scanner.addExcludeFilter(new AbstractTypeHierarchyTraversingFilter(false, false) { @Override protected boolean matchClassName(String className) { return declaringClass.equals(className); } }); return scanner.doScan(StringUtils.toStringArray(basePackages)); } protected Set<BeanDefinitionHolder> doScan(String... basePackages) { Assert.notEmpty(basePackages, "At least one base package must be specified"); Set<BeanDefinitionHolder> beanDefinitions = new LinkedHashSet<>(); for (String basePackage : basePackages) { Set<BeanDefinition> candidates = findCandidateComponents(basePackage); for (BeanDefinition candidate : candidates) { ScopeMetadata scopeMetadata = this.scopeMetadataResolver.resolveScopeMetadata(candidate); candidate.setScope(scopeMetadata.getScopeName()); String beanName = this.beanNameGenerator.generateBeanName(candidate, this.registry); if (candidate instanceof AbstractBeanDefinition) { postProcessBeanDefinition((AbstractBeanDefinition) candidate, beanName); } if (candidate instanceof AnnotatedBeanDefinition) { AnnotationConfigUtils.processCommonDefinitionAnnotations((AnnotatedBeanDefinition) candidate); } if (checkCandidate(beanName, candidate)) { BeanDefinitionHolder definitionHolder = new BeanDefinitionHolder(candidate, beanName); definitionHolder = AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry); beanDefinitions.add(definitionHolder); registerBeanDefinition(definitionHolder, this.registry); } } } return beanDefinitions; }
findCandidateComponents(basePackage)是继承下来的方法：org.springframework.context.annotation.ClassPathScanningCandidateComponentProvider#findCandidateComponents。扫描包下的所有类并进行判断，满足则加到BanDefinition集合中
/** * Scan the class path for candidate components. * @param basePackage the package to check for annotated classes * @return a corresponding Set of autodetected bean definitions */ public Set<BeanDefinition> findCandidateComponents(String basePackage) { if (this.componentsIndex != null && indexSupportsIncludeFilters()) { return addCandidateComponentsFromIndex(this.componentsIndex, basePackage); } else { return scanCandidateComponents(basePackage); } } private Set<BeanDefinition> scanCandidateComponents(String basePackage) { Set<BeanDefinition> candidates = new LinkedHashSet<>(); try { // packageSearchPath = classpath*:qz/**/*.class String packageSearchPath = ResourcePatternResolver.CLASSPATH_ALL_URL_PREFIX + resolveBasePackage(basePackage) + '/' + this.resourcePattern; // getResourcePatternResolver() 是 AnnotationConfigApplicationContext。 获取到包下的所有的类 Resource[] resources = getResourcePatternResolver().getResources(packageSearchPath); boolean traceEnabled = logger.isTraceEnabled(); boolean debugEnabled = logger.isDebugEnabled(); // 判断类是否满足条件，@Component 等注解信息，满足则加入集合 for (Resource resource : resources) { if (traceEnabled) { logger.trace("Scanning " + resource); } if (resource.isReadable()) { try { MetadataReader metadataReader = getMetadataReaderFactory().getMetadataReader(resource); if (isCandidateComponent(metadataReader)) { ScannedGenericBeanDefinition sbd = new ScannedGenericBeanDefinition(metadataReader); sbd.setSource(resource); if (isCandidateComponent(sbd)) { if (debugEnabled) { logger.debug("Identified candidate component class: " + resource); } candidates.add(sbd); } else { if (debugEnabled) { logger.debug("Ignored because not a concrete top-level class: " + resource); } } } else { if (traceEnabled) { logger.trace("Ignored because not matching any filter: " + resource); } } } catch (Throwable ex) { throw new BeanDefinitionStoreException( "Failed to read candidate component class: " + resource, ex); } } else { if (traceEnabled) { logger.trace("Ignored because not readable: " + resource); } } } } catch (IOException ex) { throw new BeanDefinitionStoreException("I/O failure during classpath scanning", ex); } return candidates; }
(3)第三步就是创建reader之后loadBeanDefinitions加载BeanDefinition信息，调用org.springframework.context.annotation.ConfigurationClassBeanDefinitionReader#loadBeanDefinitions 遍历配置文件
/** * Read {@code configurationModel}, registering bean definitions * with the registry based on its contents. */ public void loadBeanDefinitions(Set<ConfigurationClass> configurationModel) { TrackedConditionEvaluator trackedConditionEvaluator = new TrackedConditionEvaluator(); for (ConfigurationClass configClass : configurationModel) { loadBeanDefinitionsForConfigurationClass(configClass, trackedConditionEvaluator); } } /** * Read a particular {@link ConfigurationClass}, registering bean definitions * for the class itself and all of its {@link Bean} methods. */ private void loadBeanDefinitionsForConfigurationClass( ConfigurationClass configClass, TrackedConditionEvaluator trackedConditionEvaluator) { if (trackedConditionEvaluator.shouldSkip(configClass)) { String beanName = configClass.getBeanName(); if (StringUtils.hasLength(beanName) && this.registry.containsBeanDefinition(beanName)) { this.registry.removeBeanDefinition(beanName); } this.importRegistry.removeImportingClass(configClass.getMetadata().getClassName()); return; } if (configClass.isImported()) { registerBeanDefinitionForImportedConfigurationClass(configClass); } for (BeanMethod beanMethod : configClass.getBeanMethods()) { loadBeanDefinitionsForBeanMethod(beanMethod); } loadBeanDefinitionsFromImportedResources(configClass.getImportedResources()); loadBeanDefinitionsFromRegistrars(configClass.getImportBeanDefinitionRegistrars()); }
3.5 接下来调用初始化国际资源、事件等
3.6》调用 finishBeanFactoryInitialization(beanFactory); 创建非lazy的对象。org.springframework.context.support.AbstractApplicationContext#finishBeanFactoryInitialization源码如下：
protected void finishBeanFactoryInitialization(ConfigurableListableBeanFactory beanFactory) { // Initialize conversion service for this context. if (beanFactory.containsBean(CONVERSION_SERVICE_BEAN_NAME) && beanFactory.isTypeMatch(CONVERSION_SERVICE_BEAN_NAME, ConversionService.class)) { beanFactory.setConversionService( beanFactory.getBean(CONVERSION_SERVICE_BEAN_NAME, ConversionService.class)); } // Register a default embedded value resolver if no bean post-processor // (such as a PropertyPlaceholderConfigurer bean) registered any before: // at this point, primarily for resolution in annotation attribute values. if (!beanFactory.hasEmbeddedValueResolver()) { beanFactory.addEmbeddedValueResolver(strVal -> getEnvironment().resolvePlaceholders(strVal)); } // Initialize LoadTimeWeaverAware beans early to allow for registering their transformers early. String[] weaverAwareNames = beanFactory.getBeanNamesForType(LoadTimeWeaverAware.class, false, false); for (String weaverAwareName : weaverAwareNames) { getBean(weaverAwareName); } // Stop using the temporary ClassLoader for type matching. beanFactory.setTempClassLoader(null); // Allow for caching all bean definition metadata, not expecting further changes. beanFactory.freezeConfiguration(); // Instantiate all remaining (non-lazy-init) singletons. beanFactory.preInstantiateSingletons(); }
3.6.1》 最后调用在org.springframework.beans.factory.support.DefaultListableBeanFactory#preInstantiateSingletons 方法上(IoC容器中对象的创建)，逻辑如下：
public void preInstantiateSingletons() throws BeansException { if (logger.isTraceEnabled()) { logger.trace("Pre-instantiating singletons in " + this); } // Iterate over a copy to allow for init methods which in turn register new bean definitions. // While this may not be part of the regular factory bootstrap, it does otherwise work fine. List<String> beanNames = new ArrayList<>(this.beanDefinitionNames); // Trigger initialization of all non-lazy singleton beans... for (String beanName : beanNames) { RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName); // 不是抽象类，是单例且不lazy才进行下面操作 if (!bd.isAbstract() && bd.isSingleton() && !bd.isLazyInit()) { // 如果是FactoryBean if (isFactoryBean(beanName)) { // & + beanName 组成的名称 生成FactoryBean对象 Object bean = getBean(FACTORY_BEAN_PREFIX + beanName); if (bean instanceof FactoryBean) { FactoryBean<?> factory = (FactoryBean<?>) bean; boolean isEagerInit; if (System.getSecurityManager() != null && factory instanceof SmartFactoryBean) { isEagerInit = AccessController.doPrivileged( (PrivilegedAction<Boolean>) ((SmartFactoryBean<?>) factory)::isEagerInit, getAccessControlContext()); } else { isEagerInit = (factory instanceof SmartFactoryBean && ((SmartFactoryBean<?>) factory).isEagerInit()); } // 是SmartFactoryBean且isEagerInit为true生成factory对象自身的时候生成bean if (isEagerInit) { getBean(beanName); } } } else { getBean(beanName); } } } // Trigger post-initialization callback for all applicable beans... for (String beanName : beanNames) { Object singletonInstance = getSingleton(beanName); if (singletonInstance instanceof SmartInitializingSingleton) { SmartInitializingSingleton smartSingleton = (SmartInitializingSingleton) singletonInstance; if (System.getSecurityManager() != null) { AccessController.doPrivileged((PrivilegedAction<Object>) () -> { smartSingleton.afterSingletonsInstantiated(); return null; }, getAccessControlContext()); } else { smartSingleton.afterSingletonsInstantiated(); } } } }
3.6.2 》 上面代码在调用 getBean(beanName) 时候会生成对象：org.springframework.beans.factory.support.AbstractBeanFactory#getBean(java.lang.String) 源码如下：
@Override public Object getBean(String name) throws BeansException { return doGetBean(name, null, null, false); } /** * Return an instance, which may be shared or independent, of the specified bean. * @param name the name of the bean to retrieve * @param requiredType the required type of the bean to retrieve * @param args arguments to use when creating a bean instance using explicit arguments * (only applied when creating a new instance as opposed to retrieving an existing one) * @param typeCheckOnly whether the instance is obtained for a type check, * not for actual use * @return an instance of the bean * @throws BeansException if the bean could not be created */ @SuppressWarnings("unchecked") protected <T> T doGetBean( String name, @Nullable Class<T> requiredType, @Nullable Object[] args, boolean typeCheckOnly) throws BeansException { String beanName = transformedBeanName(name); Object bean; // Eagerly check singleton cache for manually registered singletons. Object sharedInstance = getSingleton(beanName); if (sharedInstance != null && args == null) { if (logger.isTraceEnabled()) { if (isSingletonCurrentlyInCreation(beanName)) { logger.trace("Returning eagerly cached instance of singleton bean '" + beanName + "' that is not fully initialized yet - a consequence of a circular reference"); } else { logger.trace("Returning cached instance of singleton bean '" + beanName + "'"); } } bean = getObjectForBeanInstance(sharedInstance, name, beanName, null); } else { // Fail if we're already creating this bean instance: // We're assumably within a circular reference. if (isPrototypeCurrentlyInCreation(beanName)) { throw new BeanCurrentlyInCreationException(beanName); } // Check if bean definition exists in this factory. BeanFactory parentBeanFactory = getParentBeanFactory(); if (parentBeanFactory != null && !containsBeanDefinition(beanName)) { // Not found -> check parent. String nameToLookup = originalBeanName(name); if (parentBeanFactory instanceof AbstractBeanFactory) { return ((AbstractBeanFactory) parentBeanFactory).doGetBean( nameToLookup, requiredType, args, typeCheckOnly); } else if (args != null) { // Delegation to parent with explicit args. return (T) parentBeanFactory.getBean(nameToLookup, args); } else if (requiredType != null) { // No args -> delegate to standard getBean method. return parentBeanFactory.getBean(nameToLookup, requiredType); } else { return (T) parentBeanFactory.getBean(nameToLookup); } } if (!typeCheckOnly) { markBeanAsCreated(beanName); } try { RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName); checkMergedBeanDefinition(mbd, beanName, args); // Guarantee initialization of beans that the current bean depends on. String[] dependsOn = mbd.getDependsOn(); if (dependsOn != null) { for (String dep : dependsOn) { if (isDependent(beanName, dep)) { throw new BeanCreationException(mbd.getResourceDescription(), beanName, "Circular depends-on relationship between '" + beanName + "' and '" + dep + "'"); } registerDependentBean(dep, beanName); try { getBean(dep); } catch (NoSuchBeanDefinitionException ex) { throw new BeanCreationException(mbd.getResourceDescription(), beanName, "'" + beanName + "' depends on missing bean '" + dep + "'", ex); } } } // Create bean instance. if (mbd.isSingleton()) { sharedInstance = getSingleton(beanName, () -> { try { return createBean(beanName, mbd, args); } catch (BeansException ex) { // Explicitly remove instance from singleton cache: It might have been put there // eagerly by the creation process, to allow for circular reference resolution. // Also remove any beans that received a temporary reference to the bean. destroySingleton(beanName); throw ex; } }); bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd); } else if (mbd.isPrototype()) { // It's a prototype -> create a new instance. Object prototypeInstance = null; try { beforePrototypeCreation(beanName); prototypeInstance = createBean(beanName, mbd, args); } finally { afterPrototypeCreation(beanName); } // create bean bean = getObjectForBeanInstance(prototypeInstance, name, beanName, mbd); } else { String scopeName = mbd.getScope(); if (!StringUtils.hasLength(scopeName)) { throw new IllegalStateException("No scope name defined for bean ´" + beanName + "'"); } Scope scope = this.scopes.get(scopeName); if (scope == null) { throw new IllegalStateException("No Scope registered for scope name '" + scopeName + "'"); } try { Object scopedInstance = scope.get(beanName, () -> { beforePrototypeCreation(beanName); try { return createBean(beanName, mbd, args); } finally { afterPrototypeCreation(beanName); } }); bean = getObjectForBeanInstance(scopedInstance, name, beanName, mbd); } catch (IllegalStateException ex) { throw new BeanCreationException(beanName, "Scope '" + scopeName + "' is not active for the current thread; consider " + "defining a scoped proxy for this bean if you intend to refer to it from a singleton", ex); } } } catch (BeansException ex) { cleanupAfterBeanCreationFailure(beanName); throw ex; } } // Check if required type matches the type of the actual bean instance. if (requiredType != null && !requiredType.isInstance(bean)) { try { T convertedBean = getTypeConverter().convertIfNecessary(bean, requiredType); if (convertedBean == null) { throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass()); } return convertedBean; } catch (TypeMismatchException ex) { if (logger.isTraceEnabled()) { logger.trace("Failed to convert bean '" + name + "' to required type '" + ClassUtils.getQualifiedName(requiredType) + "'", ex); } throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass()); } } return (T) bean; }
解释上面逻辑：
(1) 处理beanName， 根据是否是& 工厂名称处理
(2) getSingleton从缓存中获取对象。org.springframework.beans.factory.support.DefaultSingletonBeanRegistry#getSingleton(java.lang.String, boolean)
protected Object getSingleton(String beanName, boolean allowEarlyReference) { // Quick check for existing instance without full singleton lock Object singletonObject = this.singletonObjects.get(beanName); if (singletonObject == null && isSingletonCurrentlyInCreation(beanName)) { singletonObject = this.earlySingletonObjects.get(beanName); if (singletonObject == null && allowEarlyReference) { synchronized (this.singletonObjects) { // Consistent creation of early reference within full singleton lock singletonObject = this.singletonObjects.get(beanName); if (singletonObject == null) { singletonObject = this.earlySingletonObjects.get(beanName); if (singletonObject == null) { ObjectFactory<?> singletonFactory = this.singletonFactories.get(beanName); if (singletonFactory != null) { singletonObject = singletonFactory.getObject(); this.earlySingletonObjects.put(beanName, singletonObject); this.singletonFactories.remove(beanName); } } } } } } return singletonObject; }
(3) 根据单例模式和多里模式进行判断之后创建对象，单例模式创建对象的逻辑如下：
// Create bean instance. if (mbd.isSingleton()) { sharedInstance = getSingleton(beanName, () -> { try { return createBean(beanName, mbd, args); } catch (BeansException ex) { // Explicitly remove instance from singleton cache: It might have been put there // eagerly by the creation process, to allow for circular reference resolution. // Also remove any beans that received a temporary reference to the bean. destroySingleton(beanName); throw ex; } }); bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd); }
创建对象是父类的方法：org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory#createBean(java.lang.String, org.springframework.beans.factory.support.RootBeanDefinition, java.lang.Object[])。 创建对象的流程也比较繁琐。从最后一个initializeBean 方法可以看到调用其前置后置处理器。
/** * Central method of this class: creates a bean instance, * populates the bean instance, applies post-processors, etc. * @see #doCreateBean */ @Override protected Object createBean(String beanName, RootBeanDefinition mbd, @Nullable Object[] args) throws BeanCreationException { if (logger.isTraceEnabled()) { logger.trace("Creating instance of bean '" + beanName + "'"); } RootBeanDefinition mbdToUse = mbd; // Make sure bean class is actually resolved at this point, and // clone the bean definition in case of a dynamically resolved Class // which cannot be stored in the shared merged bean definition. Class<?> resolvedClass = resolveBeanClass(mbd, beanName); if (resolvedClass != null && !mbd.hasBeanClass() && mbd.getBeanClassName() != null) { mbdToUse = new RootBeanDefinition(mbd); mbdToUse.setBeanClass(resolvedClass); } // Prepare method overrides. try { mbdToUse.prepareMethodOverrides(); } catch (BeanDefinitionValidationException ex) { throw new BeanDefinitionStoreException(mbdToUse.getResourceDescription(), beanName, "Validation of method overrides failed", ex); } try { // Give BeanPostProcessors a chance to return a proxy instead of the target bean instance. Object bean = resolveBeforeInstantiation(beanName, mbdToUse); if (bean != null) { return bean; } } catch (Throwable ex) { throw new BeanCreationException(mbdToUse.getResourceDescription(), beanName, "BeanPostProcessor before instantiation of bean failed", ex); } try { Object beanInstance = doCreateBean(beanName, mbdToUse, args); if (logger.isTraceEnabled()) { logger.trace("Finished creating instance of bean '" + beanName + "'"); } return beanInstance; } catch (BeanCreationException | ImplicitlyAppearedSingletonException ex) { // A previously detected exception with proper bean creation context already, // or illegal singleton state to be communicated up to DefaultSingletonBeanRegistry. throw ex; } catch (Throwable ex) { throw new BeanCreationException( mbdToUse.getResourceDescription(), beanName, "Unexpected exception during bean creation", ex); } } /** * Actually create the specified bean. Pre-creation processing has already happened * at this point, e.g. checking {@code postProcessBeforeInstantiation} callbacks. * <p>Differentiates between default bean instantiation, use of a * factory method, and autowiring a constructor. * @param beanName the name of the bean * @param mbd the merged bean definition for the bean * @param args explicit arguments to use for constructor or factory method invocation * @return a new instance of the bean * @throws BeanCreationException if the bean could not be created * @see #instantiateBean * @see #instantiateUsingFactoryMethod * @see #autowireConstructor */ protected Object doCreateBean(String beanName, RootBeanDefinition mbd, @Nullable Object[] args) throws BeanCreationException { // Instantiate the bean. BeanWrapper instanceWrapper = null; if (mbd.isSingleton()) { instanceWrapper = this.factoryBeanInstanceCache.remove(beanName); } if (instanceWrapper == null) { instanceWrapper = createBeanInstance(beanName, mbd, args); } Object bean = instanceWrapper.getWrappedInstance(); Class<?> beanType = instanceWrapper.getWrappedClass(); if (beanType != NullBean.class) { mbd.resolvedTargetType = beanType; } // Allow post-processors to modify the merged bean definition. synchronized (mbd.postProcessingLock) { if (!mbd.postProcessed) { try { applyMergedBeanDefinitionPostProcessors(mbd, beanType, beanName); } catch (Throwable ex) { throw new BeanCreationException(mbd.getResourceDescription(), beanName, "Post-processing of merged bean definition failed", ex); } mbd.postProcessed = true; } } // Eagerly cache singletons to be able to resolve circular references // even when triggered by lifecycle interfaces like BeanFactoryAware. boolean earlySingletonExposure = (mbd.isSingleton() && this.allowCircularReferences && isSingletonCurrentlyInCreation(beanName)); if (earlySingletonExposure) { if (logger.isTraceEnabled()) { logger.trace("Eagerly caching bean '" + beanName + "' to allow for resolving potential circular references"); } addSingletonFactory(beanName, () -> getEarlyBeanReference(beanName, mbd, bean)); } // Initialize the bean instance. Object exposedObject = bean; try { populateBean(beanName, mbd, instanceWrapper); exposedObject = initializeBean(beanName, exposedObject, mbd); } catch (Throwable ex) { if (ex instanceof BeanCreationException && beanName.equals(((BeanCreationException) ex).getBeanName())) { throw (BeanCreationException) ex; } else { throw new BeanCreationException( mbd.getResourceDescription(), beanName, "Initialization of bean failed", ex); } } if (earlySingletonExposure) { Object earlySingletonReference = getSingleton(beanName, false); if (earlySingletonReference != null) { if (exposedObject == bean) { exposedObject = earlySingletonReference; } else if (!this.allowRawInjectionDespiteWrapping && hasDependentBean(beanName)) { String[] dependentBeans = getDependentBeans(beanName); Set<String> actualDependentBeans = new LinkedHashSet<>(dependentBeans.length); for (String dependentBean : dependentBeans) { if (!removeSingletonIfCreatedForTypeCheckOnly(dependentBean)) { actualDependentBeans.add(dependentBean); } } if (!actualDependentBeans.isEmpty()) { throw new BeanCurrentlyInCreationException(beanName, "Bean with name '" + beanName + "' has been injected into other beans [" + StringUtils.collectionToCommaDelimitedString(actualDependentBeans) + "] in its raw version as part of a circular reference, but has eventually been " + "wrapped. This means that said other beans do not use the final version of the " + "bean. This is often the result of over-eager type matching - consider using " + "'getBeanNamesForType' with the 'allowEagerInit' flag turned off, for example."); } } } } // Register bean as disposable. try { registerDisposableBeanIfNecessary(beanName, bean, mbd); } catch (BeanDefinitionValidationException ex) { throw new BeanCreationException( mbd.getResourceDescription(), beanName, "Invalid destruction signature", ex); } return exposedObject; } protected Object initializeBean(String beanName, Object bean, @Nullable RootBeanDefinition mbd) { if (System.getSecurityManager() != null) { AccessController.doPrivileged((PrivilegedAction<Object>) () -> { invokeAwareMethods(beanName, bean); return null; }, getAccessControlContext()); } else { invokeAwareMethods(beanName, bean); } Object wrappedBean = bean; if (mbd == null || !mbd.isSynthetic()) { wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName); } try { invokeInitMethods(beanName, wrappedBean, mbd); } catch (Throwable ex) { throw new BeanCreationException( (mbd != null ? mbd.getResourceDescription() : null), beanName, "Invocation of init method failed", ex); } if (mbd == null || !mbd.isSynthetic()) { wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName); } return wrappedBean; }
doCreateBean 方法的 addSingletonFactory 方法会将对象工厂和对象加入缓存。
加下来就是研究依赖注入，@Autowired 的自注入机制。
补充： BeanFactoryPostProcessor 可以对bean的定义(配置元数据)进行处理， 他是在注册数据之后实例化数据之前被调用的，因此可以用于修改BeanDefinition的信息, 如果有多个，可以通过Order定义其顺序。例如：
package qz; import jdk.nashorn.internal.runtime.logging.Logger; import org.springframework.beans.BeansException; import org.springframework.beans.factory.config.BeanDefinition; import org.springframework.beans.factory.config.BeanFactoryPostProcessor; import org.springframework.beans.factory.config.ConfigurableListableBeanFactory; import org.springframework.stereotype.Component; import java.util.Arrays; /** * @author: 乔利强 * @date: 2021/2/9 21:49 * @description: */ @Component public class MyBeanFactoryPostProcessor implements BeanFactoryPostProcessor { @Override public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException { String[] beanDefinitionNames = beanFactory.getBeanDefinitionNames(); System.out.println("beanDefinitionNames:" + Arrays.toString(beanDefinitionNames)); // 可以获取到BeanDefinition 做一些处理 BeanDefinition userService = beanFactory.getBeanDefinition("userService"); String scope = userService.getScope(); System.out.println(scope); } }
另外创建一个Service注入IoC：
package qz; import org.springframework.stereotype.Component; import javax.annotation.PostConstruct; @Component //@Scope(proxyMode = ScopedProxyMode.TARGET_CLASS) //@Lazy public class UserService { public UserService() { System.out.println("=============UserService====="); } public String method1() { System.out.println("method1"); return "method1"; } @PostConstruct public void post() { System.out.println("post============="); } }
结果：(可以看出是在实例化之前，注入之后调用的)
beanDefinitionNames:[org.springframework.context.annotation.internalConfigurationAnnotationProcessor, org.springframework.context.annotation.internalAutowiredAnnotationProcessor, org.springframework.context.annotation.internalCommonAnnotationProcessor, org.springframework.context.event.internalEventListenerProcessor, org.springframework.context.event.internalEventListenerFactory, mainApp, myBeanFactoryPostProcessor, userService] singleton =============UserService===== post=============
补充：还有一个是 BeanFactoryPostProcessor 的子接口 BeanDefinitionRegistryPostProcessor，这个会在 BeanFactoryPostProcessor 之前被调用，用于动态的注入beanDefition信息，参考org.springframework.context.annotation.ConfigurationClassPostProcessor，测试如下：
package qz; import org.springframework.beans.BeansException; import org.springframework.beans.factory.config.ConfigurableListableBeanFactory; import org.springframework.beans.factory.support.BeanDefinitionRegistry; import org.springframework.beans.factory.support.BeanDefinitionRegistryPostProcessor; import org.springframework.stereotype.Component; /** * @author: 乔利强 * @date: 2021/2/10 10:29 * @description: */ @Component public class MyBeanDefinitionRegistryPostProcessor implements BeanDefinitionRegistryPostProcessor { @Override public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException { System.out.println("MyBeanDefinitionRegistryPostProcessor postProcessBeanDefinitionRegistry"); } @Override public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException { System.out.println("MyBeanDefinitionRegistryPostProcessor postProcessBeanFactory"); } }
结果：
MyBeanDefinitionRegistryPostProcessor postProcessBeanDefinitionRegistry MyBeanDefinitionRegistryPostProcessor postProcessBeanFactory beanDefinitionNames:[org.springframework.context.annotation.internalConfigurationAnnotationProcessor, org.springframework.context.annotation.internalAutowiredAnnotationProcessor, org.springframework.context.annotation.internalCommonAnnotationProcessor, org.springframework.context.event.internalEventListenerProcessor, org.springframework.context.event.internalEventListenerFactory, mainApp, myBeanDefinitionRegistryPostProcessor, myBeanFactoryPostProcessor, userService] singleton =============UserService===== post=============
补充：根据包名获取所有的类资源：AnnotationConfigApplicationContext 本身实现了ResourceLoader接口
AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(); Resource[] resource = applicationContext.getResources("classpath*:qz/**/*.class"); System.out.println(Arrays.toString(resource));
补充： ListableBeanFactory 接口继承自BeanFactory 接口，扩展了许多有用的方法，
根据类型获取beanname org.springframework.beans.factory.ListableBeanFactory#getBeanNamesForType(org.springframework.core.ResolvableType) 根据类型获取beanName和bean org.springframework.beans.factory.ListableBeanFactory#getBeansOfType(java.lang.Class<T>) 根据注解获取beanNames org.springframework.beans.factory.ListableBeanFactory#getBeanNamesForAnnotation 根据注解获取beanNames和bean org.springframework.beans.factory.ListableBeanFactory#getBeansWithAnnotation
并且在 DefaultListableBeanFactory 类中都给出了默认实现。比如：
AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(App.class); // 根据类型获取其beanNames String[] beanNamesForType = applicationContext.getBeanNamesForType(UserDao.class); System.out.println(Arrays.toString(beanNamesForType)); // 根据类型获取其beanNames和bean Map<String, UserDao> beansOfType = applicationContext.getBeansOfType(UserDao.class); System.out.println(beansOfType); // 获取带有某个注解的beanName和bean Map<String, Object> beansWithAnnotation = applicationContext.getBeansWithAnnotation(Anno1.class); System.out.println(beansWithAnnotation);
补充：IoC refresh 方法最后还有一个方法：这个方法主要调用：org.springframework.context.Lifecycle 接口在spring容器加载和初始化完毕执行一些操作， 其执行过程如下：
// Last step: publish corresponding event. finishRefresh();
调用org.springframework.context.support.AbstractApplicationContext#finishRefresh
调用org.springframework.context.support.DefaultLifecycleProcessor#onRefresh
调用org.springframework.context.support.DefaultLifecycleProcessor#startBeans
调用org.springframework.context.support.DefaultLifecycleProcessor.LifecycleGroup#start
调用org.springframework.context.support.DefaultLifecycleProcessor#doStart
比如：
package cn.qz.user; import org.springframework.context.SmartLifecycle; import org.springframework.stereotype.Component; @Component public class MyLifecyle implements SmartLifecycle { private Boolean isRunning = false; @Override public boolean isAutoStartup() { return true; } @Override public void stop(Runnable callback) { callback.run(); } @Override public void start() { System.out.println("SmartLifecycleImpl is starting ...."); isRunning = true; } @Override public void stop() { System.out.println("SmartLifecycleImpl is stopped."); } /** * 执行start()方法前会用它来判断是否执行，返回为true时，start()方法不执行 */ @Override public boolean isRunning() { return isRunning; } @Override public int getPhase() { return 0; } }