一.源码分析
1.创建ApplicationContext
在上面spring boot启动中的分析中，发现在SpringApplication.run中创建了ApplicationContext 并且在context = this.createApplicationContext();中创建上下文。
public ConfigurableApplicationContext run(String... args) {
StopWatch stopWatch = new StopWatch();
stopWatch.start();
ConfigurableApplicationContext context = null;
Collection<SpringBootExceptionReporter> exceptionReporters = new ArrayList();
this.configureHeadlessProperty();
SpringApplicationRunListeners listeners = this.getRunListeners(args);
listeners.starting();
Collection exceptionReporters;
try {
ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);
ConfigurableEnvironment environment = this.prepareEnvironment(listeners, applicationArguments);
this.configureIgnoreBeanInfo(environment);
Banner printedBanner = this.printBanner(environment);
//创建spring上下文
context = this.createApplicationContext();
exceptionReporters = this.getSpringFactoriesInstances(SpringBootExceptionReporter.class, new Class[]{ConfigurableApplicationContext.class}, context);
this.prepareContext(context, environment, listeners, applicationArguments, printedBanner);
//注入bean
this.refreshContext(context);
this.afterRefresh(context, applicationArguments);
stopWatch.stop();
if (this.logStartupInfo) {
(new StartupInfoLogger(this.mainApplicationClass)).logStarted(this.getApplicationLog(), stopWatch);
}
listeners.started(context);
this.callRunners(context, applicationArguments);
} catch (Throwable var10) {
this.handleRunFailure(context, var10, exceptionReporters, listeners);
throw new IllegalStateException(var10);
}
try {
listeners.running(context);
return context;
} catch (Throwable var9) {
this.handleRunFailure(context, var9, exceptionReporters, (SpringApplicationRunListeners)null);
throw new IllegalStateException(var9);
}
}其中创建的ApplicationContext类型如下，创建的类型为AnnotationConfigServletWebServerApplicationContext，所以ioc我们可以将断点打在AnnotationConfigApplicationContext中。
protected ConfigurableApplicationContext createApplicationContext() {
Class<?> contextClass = this.applicationContextClass;
if (contextClass == null) {
try {
switch(this.webApplicationType) {
case SERVLET:
contextClass = Class.forName("org.springframework.boot.web.servlet.context.AnnotationConfigServletWebServerApplicationContext");
break;
case REACTIVE:
contextClass = Class.forName("org.springframework.boot.web.reactive.context.AnnotationConfigReactiveWebServerApplicationContext");
break;
default:
contextClass = Class.forName("org.springframework.context.annotation.AnnotationConfigApplicationContext");
}
} catch (ClassNotFoundException var3) {
throw new IllegalStateException("Unable create a default ApplicationContext, please specify an ApplicationContextClass", var3);
}
}
return (ConfigurableApplicationContext)BeanUtils.instantiateClass(contextClass);
}2 进入AbstractApplicationContext的refresh()方法
在refreshContext最终会调用AbstractApplicationContext的refresh方法。
this.refreshContext(context);
@Override
public void refresh() throws BeansException, IllegalStateException {
synchronized (this.startupShutdownMonitor) {
// Prepare this context for refreshing.
//刷新上下文环境
prepareRefresh();
// Tell the subclass to refresh the internal bean factory.
//这里是在子类中启动 refreshBeanFactory() 的地方
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
// Prepare the bean factory for use in this context.
//准备bean工厂，以便在此上下文中使用
prepareBeanFactory(beanFactory);
try {
// Allows post-processing of the bean factory in context subclasses.
//设置 beanFactory 的后置处理
postProcessBeanFactory(beanFactory);
// Invoke factory processors registered as beans in the context.
//调用 BeanFactory 的后处理器，这些处理器是在Bean 定义中向容器注册的
invokeBeanFactoryPostProcessors(beanFactory);
// Register bean processors that intercept bean creation.
//注册Bean的后处理器，在Bean创建过程中调用
registerBeanPostProcessors(beanFactory);
// Initialize message source for this context.
//对上下文中的消息源进行初始化
initMessageSource();
// Initialize event multicaster for this context.
//初始化上下文中的事件机制
initApplicationEventMulticaster();
// Initialize other special beans in specific context subclasses.
//初始化其他特殊的Bean
onRefresh();
// Check for listener beans and register them.
//检查监听Bean并且将这些监听Bean向容器注册
registerListeners();
// Instantiate all remaining (non-lazy-init) singletons.
//实例化所有的（non-lazy-init）单件
finishBeanFactoryInitialization(beanFactory);
// Last step: publish corresponding event.
//发布容器事件，结束Refresh过程
finishRefresh();
} catch (BeansException ex) {
if (logger.isWarnEnabled()) {
logger.warn("Exception encountered during context initialization - " +
"cancelling refresh attempt: " + ex);
}
// Destroy already created singletons to avoid dangling resources.
destroyBeans();
// Reset 'active' flag.
cancelRefresh(ex);
// Propagate exception to caller.
throw ex;
} finally {
// Reset common introspection caches in Spring's core, since we
// might not ever need metadata for singleton beans anymore...
resetCommonCaches();
}
}
}
1.this.obtainFreshBeanFactory();装载初始化的bean
protected final void refreshBeanFactory() throws BeansException {
if (this.hasBeanFactory()) {
this.destroyBeans();
this.closeBeanFactory();
}
try {
//创建BeanFactory
DefaultListableBeanFactory beanFactory = this.createBeanFactory();
beanFactory.setSerializationId(this.getId());
this.customizeBeanFactory(beanFactory);
//载入bean
this.loadBeanDefinitions(beanFactory);
synchronized(this.beanFactoryMonitor) {
this.beanFactory = beanFactory;
}
} catch (IOException var5) {
throw new ApplicationContextException("I/O error parsing bean definition source for " + this.getDisplayName(), var5);
}
}2.this.prepareBeanFactory(beanFactory);
protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {
//添加类加载器
beanFactory.setBeanClassLoader(this.getClassLoader());
// 配置EL表达式
beanFactory.setBeanExpressionResolver(new StandardBeanExpressionResolver(beanFactory.getBeanClassLoader()));
// 添加属性编辑器 PropertyEditor
beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, this.getEnvironment()));
//添加后置处理器
beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));
//忽略以下类
beanFactory.ignoreDependencyInterface(EnvironmentAware.class);
beanFactory.ignoreDependencyInterface(EmbeddedValueResolverAware.class);
beanFactory.ignoreDependencyInterface(ResourceLoaderAware.class);
beanFactory.ignoreDependencyInterface(ApplicationEventPublisherAware.class);
beanFactory.ignoreDependencyInterface(MessageSourceAware.class);
beanFactory.ignoreDependencyInterface(ApplicationContextAware.class);
//放入resolvableDependencies属性
beanFactory.registerResolvableDependency(BeanFactory.class, beanFactory);
beanFactory.registerResolvableDependency(ResourceLoader.class, this);
beanFactory.registerResolvableDependency(ApplicationEventPublisher.class, this);
beanFactory.registerResolvableDependency(ApplicationContext.class, this);
beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(this));
if (beanFactory.containsBean("loadTimeWeaver")) {
beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));
beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
}
//以下为单例
if (!beanFactory.containsLocalBean("environment")) {
beanFactory.registerSingleton("environment", this.getEnvironment());
}
if (!beanFactory.containsLocalBean("systemProperties")) {
beanFactory.registerSingleton("systemProperties", this.getEnvironment().getSystemProperties());
}
if (!beanFactory.containsLocalBean("systemEnvironment")) {
beanFactory.registerSingleton("systemEnvironment", this.getEnvironment().getSystemEnvironment());
}
}3.postProcessBeanFactory
postProcessBeanFactory()方法向上下文中添加了一系列的Bean的后置处理器。后置处理器工作的时机是在所有的beanDenifition加载完成之后，bean实例化之前执行。简单来说Bean的后置处理器可以修改BeanDefinition的属性信息。
4.invokeBeanFactoryPostProcessors-->parse
public void refresh() throws BeansException, IllegalStateException {
...
this.invokeBeanFactoryPostProcessors(beanFactory);
...
}
protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {
PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory, this.getBeanFactoryPostProcessors());
...
}
public static void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {
...
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
currentRegistryProcessors.clear();
...
}
private static void invokeBeanDefinitionRegistryPostProcessors(Collection<? extends BeanDefinitionRegistryPostProcessor> postProcessors,
...
postProcessor.postProcessBeanDefinitionRegistry(registry);
}
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) {
...
this.processConfigBeanDefinitions(registry);
...
}
public void processConfigBeanDefinitions(BeanDefinitionRegistry registry) {
...
parser.parse(candidates);
...
}// ConfigurationClassParser类
public void parse(Set<BeanDefinitionHolder> configCandidates) {
Iterator var2 = configCandidates.iterator();
while(var2.hasNext()) {
BeanDefinitionHolder holder = (BeanDefinitionHolder)var2.next();
BeanDefinition bd = holder.getBeanDefinition();
try {
//SpringBoot项目项目启动时AnnotatedBeanDefinition 上面注入的启动类的BeanDefinition
if (bd instanceof AnnotatedBeanDefinition) {
this.parse(((AnnotatedBeanDefinition)bd).getMetadata(), holder.getBeanName());
} else if (bd instanceof AbstractBeanDefinition && ((AbstractBeanDefinition)bd).hasBeanClass()) {
this.parse(((AbstractBeanDefinition)bd).getBeanClass(), holder.getBeanName());
} else {
this.parse(bd.getBeanClassName(), holder.getBeanName());
}
} catch (BeanDefinitionStoreException var6) {
throw var6;
} catch (Throwable var7) {
throw new BeanDefinitionStoreException("Failed to parse configuration class [" + bd.getBeanClassName() + "]", var7);
}
// 加载默认的配置 就是加载.pom中的的依赖
this.deferredImportSelectorHandler.process();
}
protected final void parse(AnnotationMetadata metadata, String beanName) throws IOException {
this.processConfigurationClass(new ConfigurationClass(metadata, beanName));
}
protected void processConfigurationClass(ConfigurationClass configClass) throws IOException {
...
do {
//递归处理Bean，如果有父类，递归处理，直到顶层父类
sourceClass = this.doProcessConfigurationClass(configClass, sourceClass);
}
...
}
}
// ConfigurationClassParser类
protected final SourceClass doProcessConfigurationClass(ConfigurationClass configClass, SourceClass sourceClass)
throws IOException {
// Recursively process any member (nested) classes first
//首先递归处理内部类，（SpringBoot项目的主类一般没有内部类）
processMemberClasses(configClass, sourceClass);
// Process any @PropertySource annotations
// 针对 @PropertySource 注解的属性配置处理
for (AnnotationAttributes propertySource : AnnotationConfigUtils.attributesForRepeatable(
sourceClass.getMetadata(), PropertySources.class,
org.springframework.context.annotation.PropertySource.class)) {
if (this.environment instanceof ConfigurableEnvironment) {
processPropertySource(propertySource);
} else {
logger.warn("Ignoring @PropertySource annotation on [" + sourceClass.getMetadata().getClassName() +
"]. Reason: Environment must implement ConfigurableEnvironment");
}
}
// Process any @ComponentScan annotations
// 根据 @ComponentScan 注解，扫描项目中的Bean（SpringBoot 启动类上有该注解）
Set<AnnotationAttributes> componentScans = AnnotationConfigUtils.attributesForRepeatable(
sourceClass.getMetadata(), ComponentScans.class, ComponentScan.class);
if (!componentScans.isEmpty() &&
!this.conditionEvaluator.shouldSkip(sourceClass.getMetadata(), ConfigurationPhase.REGISTER_BEAN)) {
for (AnnotationAttributes componentScan : componentScans) {
// The config class is annotated with @ComponentScan -> perform the scan immediately
// 立即执行扫描，（SpringBoot项目为什么是从主类所在的包扫描，这就是关键了）
Set<BeanDefinitionHolder> scannedBeanDefinitions =
this.componentScanParser.parse(componentScan, sourceClass.getMetadata().getClassName());
// Check the set of scanned definitions for any further config classes and parse recursively if needed
for (BeanDefinitionHolder holder : scannedBeanDefinitions) {
BeanDefinition bdCand = holder.getBeanDefinition().getOriginatingBeanDefinition();
if (bdCand == null) {
bdCand = holder.getBeanDefinition();
}
// 检查是否是ConfigurationClass（是否有configuration/component两个注解），如果是，递归查找该类相关联的配置类。
// 所谓相关的配置类，比如@Configuration中的@Bean定义的bean。或者在有@Component注解的类上继续存在@Import注解。
if (ConfigurationClassUtils.checkConfigurationClassCandidate(bdCand, this.metadataReaderFactory)) {
parse(bdCand.getBeanClassName(), holder.getBeanName());
}
}
}
}
// Process any @Import annotations
//递归处理 @Import 注解（SpringBoot项目中经常用的各种@Enable*** 注解基本都是封装的@Import）
processImports(configClass, sourceClass, getImports(sourceClass), true);
// Process any @ImportResource annotations
AnnotationAttributes importResource =
AnnotationConfigUtils.attributesFor(sourceClass.getMetadata(), ImportResource.class);
if (importResource != null) {
String[] resources = importResource.getStringArray("locations");
Class<? extends BeanDefinitionReader> readerClass = importResource.getClass("reader");
for (String resource : resources) {
String resolvedResource = this.environment.resolveRequiredPlaceholders(resource);
configClass.addImportedResource(resolvedResource, readerClass);
}
}
// Process individual @Bean methods
Set<MethodMetadata> beanMethods = retrieveBeanMethodMetadata(sourceClass);
for (MethodMetadata methodMetadata : beanMethods) {
configClass.addBeanMethod(new BeanMethod(methodMetadata, configClass));
}
// Process default methods on interfaces
processInterfaces(configClass, sourceClass);
// Process superclass, if any
if (sourceClass.getMetadata().hasSuperClass()) {
String superclass = sourceClass.getMetadata().getSuperClassName();
if (superclass != null && !superclass.startsWith("java") &&
!this.knownSuperclasses.containsKey(superclass)) {
this.knownSuperclasses.put(superclass, configClass);
// Superclass found, return its annotation metadata and recurse
return sourceClass.getSuperClass();
}
}
// No superclass -> processing is complete
return null;
}进入Set<BeanDefinitionHolder> scannedBeanDefinitions = this.componentScanParser.parse(componentScan, sourceClass.getMetadata().getClassName());
public Set<BeanDefinitionHolder> parse(AnnotationAttributes componentScan, final String declaringClass) {
...
return scanner.doScan(StringUtils.toStringArray(basePackages));
}
protected Set<BeanDefinitionHolder> doScan(String... basePackages) {
for(int var5 = 0; var5 < var4; ++var5) {
String basePackage = var3[var5];
//扫描注解 查到bean 转为BeanDefinition
Set<BeanDefinition> candidates = this.findCandidateComponents(basePackage);
Iterator var8 = candidates.iterator();
while(var8.hasNext()) {
BeanDefinition candidate = (BeanDefinition)var8.next();
ScopeMetadata scopeMetadata = this.scopeMetadataResolver.resolveScopeMetadata(candidate);
candidate.setScope(scopeMetadata.getScopeName());
String beanName = this.beanNameGenerator.generateBeanName(candidate, this.registry);
if (candidate instanceof AbstractBeanDefinition) {
this.postProcessBeanDefinition((AbstractBeanDefinition)candidate, beanName);
}
if (candidate instanceof AnnotatedBeanDefinition) {
AnnotationConfigUtils.processCommonDefinitionAnnotations((AnnotatedBeanDefinition)candidate);
}
if (this.checkCandidate(beanName, candidate)) {
BeanDefinitionHolder definitionHolder = new BeanDefinitionHolder(candidate, beanName);
definitionHolder = AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry);
beanDefinitions.add(definitionHolder);
//注入ioc
this.registerBeanDefinition(definitionHolder, this.registry);
}
}
}
return beanDefinitions;
}二.个人理解，获取bean的过程
- 获取要扫描的包的地址。
- 通过注解扫描出bean 。
- BeanDefinitionReaderUtils.registerBeanDefinition(definitionHolder, this.registry);将该BeanDefinition注册到IoC容器的beanDefinitionMap中 。
public static void registerBeanDefinition(BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry) throws BeanDefinitionStoreException {
String beanName = definitionHolder.getBeanName();
registry.registerBeanDefinition(beanName, definitionHolder.getBeanDefinition());
String[] aliases = definitionHolder.getAliases();
if (aliases != null) {
String[] var4 = aliases;
int var5 = aliases.length;
for(int var6 = 0; var6 < var5; ++var6) {
String alias = var4[var6];
registry.registerAlias(beanName, alias);
}
}
}其中在 parse 中的 this.deferredImportSelectorHandler.process(); 加载pom文件中的依赖。
其中后置处理器可以修改BeanDefinition,可以参考以下实例
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三.bean的生命周期
- 实例化Bean对象，这个时候Bean的对象是非常低级的，基本不能够被我们使用，因为连最基本的属性都没有设置，可以理解为连Autowired注解都是没有解析的；
- 填充属性，当做完这一步，Bean对象基本是完整的了，可以理解为Autowired注解已经解析完毕，依赖注入完成了；
- 如果Bean实现了BeanNameAware接口，则调用setBeanName方法；
- 如果Bean实现了BeanClassLoaderAware接口，则调用setBeanClassLoader方法；
- 如果Bean实现了BeanFactoryAware接口，则调用setBeanFactory方法；
- 调用BeanPostProcessor的postProcessBeforeInitialization方法；
- 如果Bean实现了InitializingBean接口，调用afterPropertiesSet方法；
- 如果Bean定义了init-method方法，则调用Bean的init-method方法；
- 调用BeanPostProcessor的postProcessAfterInitialization方法；当进行到这一步，Bean已经被准备就绪了，一直停留在应用的上下文中，直到被销毁；
- 如果应用的上下文被销毁了，如果Bean实现了DisposableBean接口，则调用destroy方法，如果Bean定义了destory-method声明了销毁方法也会被调用。
