博信信息网java-SpringBoot自动装配
1.为什么要有springboot1.1spring的优缺点
优点：提供了ioc和aop等强大的功能让开发人员专注业务代码
缺点：配置复杂，项目依赖繁琐，依赖版本稍有不对就会造成兼容问题
2.springboot如何解决这些问题2.1起步依赖：只需依赖一个项目就可达到spring依赖多个包的功能，即将具备某种功能的坐标打包到一起。
两个核心依赖spring-boot-starter-parent和spring-boot-starter-web：
spring-boot-starter-parent指定jar包版本
spring-boot-starter-web指定web开发jar包
2.2自动配置：只需引入相关的包，springboot会在启动时将这些配置的bean给初始化
通过在main函数加上注解@SpringBootApplication，该注解主要包含三个关键注解
· @configuration注解：代表它是一个配置类，我们可以在该类中申明一些方法，返回bean
· @EnableAutoConfiguration：初始化bean
• @Import(AutoConfigurationImportSelector.class) ： 实现自动配置的功能，从classpath下所有jar包的META-INF\spring-autoconfigure-metadata.properties拿到指定的bean初始化限制条件，然后从spring.factories里拿到指定的类初始化bean，进行初始化。
其他注解：
• @AutoConfigurationPackage：实例化启动类所在包下面的所有bean
· @ComponentScan:指定扫描包范围，配和@AutoConfigurationPackage使用，可过滤不想初始化的bean
3.具体实现看启动函数：
@SpringBootApplication public class DemoApplication
{
public static void main(String[] args)
{
SpringApplication.run(DemoApplication.class, args);
}
} public SpringApplication(ResourceLoader resourceLoader, Object... sources) {
this.resourceLoader = resourceLoader;
initialize(sources);
}进入initialize方法
private void initialize(Object[] sources) {
if (sources != null && sources.length > 0) {
this.sources.addAll(Arrays.asList(sources));
}
this.webEnvironment = deduceWebEnvironment();
setInitializers((Collection) getSpringFactoriesInstances(
ApplicationContextInitializer.class));
setListeners((Collection) getSpringFactoriesInstances(ApplicationListener.class));
this.mainApplicationClass = deduceMainApplicationClass();
}进入deduceWebEnvironment
private boolean deduceWebEnvironment() {
for (String className : WEB_ENVIRONMENT_CLASSES) {
if (!ClassUtils.isPresent(className, null)) {
return false;
}
}
return true;
}此方法是用来判断当前应用是什么类型：
private static final String[] WEB_ENVIRONMENT_CLASSES = { "javax.servlet.Servlet",
"org.springframework.web.context.ConfigurableWebApplicationContext" };需要上面两个类都存在才说明当前是个web应用.
再看setInitializers和setListeners方法，都调用了getSpringFactoriesInstances方法：
private <T> Collection<? extends T> getSpringFactoriesInstances(Class<T> type,
Class<?>[] parameterTypes, Object... args) {
ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
// Use names and ensure unique to protect against duplicates
Set<String> names = new LinkedHashSet<String>(
SpringFactoriesLoader.loadFactoryNames(type, classLoader));
List<T> instances = createSpringFactoriesInstances(type, parameterTypes,
classLoader, args, names);
AnnotationAwareOrderComparator.sort(instances);
return instances;
}getSpringFactoriesInstances方法是扫描路径下所有META-INF\spring.factories里
符合type参数指定的接口的实现类并实例化，然后排序。
最后this.mainApplicationClass = deduceMainApplicationClass()找出启动main函数在的主类。
public ConfigurableApplicationContext run(String... args) {
StopWatch stopWatch = new StopWatch();
stopWatch.start();
ConfigurableApplicationContext context = null;
FailureAnalyzers analyzers = null;
configureHeadlessProperty();
SpringApplicationRunListeners listeners = getRunListeners(args);
listeners.started();
try {
ApplicationArguments applicationArguments = new DefaultApplicationArguments(
args);
ConfigurableEnvironment environment = prepareEnvironment(listeners,
applicationArguments);
Banner printedBanner = printBanner(environment);
context = createApplicationContext();
analyzers = new FailureAnalyzers(context);
prepareContext(context, environment, listeners, applicationArguments,
printedBanner);
refreshContext(context);
afterRefresh(context, applicationArguments);
listeners.finished(context, null);
stopWatch.stop();
if (this.logStartupInfo) {
new StartupInfoLogger(this.mainApplicationClass)
.logStarted(getApplicationLog(), stopWatch);
}
return context;
}
catch (Throwable ex) {
handleRunFailure(context, listeners, analyzers, ex);
throw new IllegalStateException(ex);
}
}首先看getRunListeners方法：
private SpringApplicationRunListeners getRunListeners(String[] args) {
Class<?>[] types = new Class<?>[] { SpringApplication.class, String[].class };
return new SpringApplicationRunListeners(logger, getSpringFactoriesInstances(
SpringApplicationRunListener.class, types, this, args));
}同样是找到并实例化SpringApplicationRunListener的实现类；
再看listeners.started()做了什么：
一路跟进去
最终调用了listener.onApplicationEvent(event)方法，该方法有很多子类的实现，内容大概就是做一些准备工作，比如org.springframework.boot.context.logging.LoggingApplicationListener做的就是
private void onApplicationStartedEvent(ApplicationStartedEvent event) {
this.loggingSystem = LoggingSystem
.get(event.getSpringApplication().getClassLoader());
this.loggingSystem.beforeInitialize();
}日志初始化的一些准备工作。
接下来看
ApplicationArguments applicationArguments = new DefaultApplicationArguments(
args);初始化main函数的参数；
ConfigurableEnvironment environment = prepareEnvironment(listeners,
applicationArguments); private ConfigurableEnvironment prepareEnvironment(
SpringApplicationRunListeners listeners,
ApplicationArguments applicationArguments) {
// Create and configure the environment
ConfigurableEnvironment environment = getOrCreateEnvironment();
configureEnvironment(environment, applicationArguments.getSourceArgs());
listeners.environmentPrepared(environment);
if (isWebEnvironment(environment) && !this.webEnvironment) {
environment = convertToStandardEnvironment(environment);
}
return environment;
}进入getOrCreateEnvironment：
private ConfigurableEnvironment getOrCreateEnvironment() {
if (this.environment != null) {
return this.environment;
}
if (this.webEnvironment) {
return new StandardServletEnvironment();
}
return new StandardEnvironment();
}一般都是webEnvironment，所以返回new StandardServletEnvironment()；
protected void configureEnvironment(ConfigurableEnvironment environment,
String[] args) {
configurePropertySources(environment, args);
configureProfiles(environment, args);
}
protected void configurePropertySources(ConfigurableEnvironment environment,
String[] args) {
MutablePropertySources sources = environment.getPropertySources();
if (this.defaultProperties != null && !this.defaultProperties.isEmpty()) {
sources.addLast(
new MapPropertySource("defaultProperties", this.defaultProperties));
}
if (this.addCommandLineProperties && args.length > 0) {
String name = CommandLinePropertySource.COMMAND_LINE_PROPERTY_SOURCE_NAME;
if (sources.contains(name)) {
PropertySource<?> source = sources.get(name);
CompositePropertySource composite = new CompositePropertySource(name);
composite.addPropertySource(new SimpleCommandLinePropertySource(
name + "-" + args.hashCode(), args));
composite.addPropertySource(source);
sources.replace(name, composite);
}
else {
sources.addFirst(new SimpleCommandLinePropertySource(args));
}
}
}defaultProperties 是额外属性配置，可以在构造SpringBootApplication时通过setDefaultProperties设置；
如果配置了args，且命令行有名为commandLineArgs的参数，则会用命令行参数替换或新增该PropertySource。
再看configureProfiles，我的版本是个空方法（spring-boot-2.7.3）
看了下其他版本的，大概就是读取properties里的key为spring.profiles.active的配置项，配置到Environment。
继续看ConfigurationPropertySources.attach(environment)
/**
* Attach a {@link ConfigurationPropertySource} support to the specified
* {@link Environment}. Adapts each {@link PropertySource} managed by the environment
* to a {@link ConfigurationPropertySource} and allows classic
* {@link PropertySourcesPropertyResolver} calls to resolve using
* {@link ConfigurationPropertyName configuration property names}.
* <p>
* The attached resolver will dynamically track any additions or removals from the
* underlying {@link Environment} property sources.
* @param environment the source environment (must be an instance of
* {@link ConfigurableEnvironment})
* @see #get(Environment)
*/
public static void attach(Environment environment) {
Assert.isInstanceOf(ConfigurableEnvironment.class, environment);
MutablePropertySources sources = ((ConfigurableEnvironment) environment).getPropertySources();
PropertySource<?> attached = getAttached(sources);
if (attached == null || !isUsingSources(attached, sources)) {
attached = new ConfigurationPropertySourcesPropertySource(ATTACHED_PROPERTY_SOURCE_NAME,
new SpringConfigurationPropertySources(sources));
}
sources.remove(ATTACHED_PROPERTY_SOURCE_NAME);
sources.addFirst(attached);
}该方法将ConfigurationPropertySource和environment绑定起来。
listeners.environmentPrepared(bootstrapContext, environment)方法为监听器准备环境，过程有点复杂，以后再看。
DefaultPropertiesPropertySource.moveToEnd(environment)将默认环境移到最后，这样优先级最高？
bindToSpringApplication(environment)将环境和主类绑定。
if (!this.isCustomEnvironment) {
EnvironmentConverter environmentConverter = new EnvironmentConverter(getClassLoader());
environment = environmentConverter.convertEnvironmentIfNecessary(environment, deduceEnvironmentClass());
}将环境转化为标准环境
environment为ApplicationServletEnvironment，是StandEnvironment的子类，不用转。
ConfigurationPropertySources.attach(environment)再绑定一次环境和source。
prepareEnvironment结束了，再看configureIgnoreBeanInfo(environment)：
private void configureIgnoreBeanInfo(ConfigurableEnvironment environment) {
if (System.getProperty(CachedIntrospectionResults.IGNORE_BEANINFO_PROPERTY_NAME) == null) {
Boolean ignore = environment.getProperty(CachedIntrospectionResults.IGNORE_BEANINFO_PROPERTY_NAME,
Boolean.class, Boolean.TRUE);
System.setProperty(CachedIntrospectionResults.IGNORE_BEANINFO_PROPERTY_NAME, ignore.toString());
}
}
将environment的spring.beaninfo.ignore的值设置到系统属性。
Banner printedBanner = printBanner(environment);
打印banner，
. ____ _ __ _ _
/\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
\\/ ___)| |_)| | | | | || (_| | ) ) ) )
' |____| .__|_| |_|_| |_\__, | / / / /
=========|_|==============|___/=/_/_/_/
:: Spring Boot :: (v2.2.5.RELEASE)如上图所示的，是我们每次启动 SpringBoot 项目时就会在控制器输出的内容，这个就是 Banner 。这部分代码不重要。context = createApplicationContext();
/**
* {@link ApplicationContextFactory} registered in {@code spring.factories} to support
* {@link AnnotationConfigServletWebServerApplicationContext}.
*/
static class Factory implements ApplicationContextFactory {
@Override
public ConfigurableApplicationContext create(WebApplicationType webApplicationType) {
return (webApplicationType != WebApplicationType.SERVLET) ? null
: new AnnotationConfigServletWebServerApplicationContext();
}
}创建了一个AnnotationConfigServletWebServerApplicationContext。
AnnotationConfigServletWebServerApplicationContext继承自GenericApplicationContext，
/**
* Create a new GenericApplicationContext.
* @see #registerBeanDefinition
* @see #refresh
*/
public GenericApplicationContext() {
this.beanFactory = new DefaultListableBeanFactory();
}
父类实例化的时候创建了一个DefaultListableBeanFactory。
子类是泪花的时候创建了AnnotatedBeanDefinitionReader和ClassPathBeanDefinitionScanner，这两个类是用来读取condition注解和定义哪些类应该被实例化（@Component，@Service，@Resources这种）
/**
* Create a new {@link AnnotationConfigServletWebServerApplicationContext} with the
* given {@code DefaultListableBeanFactory}. The context needs to be populated through
* {@link #register} calls and then manually {@linkplain #refresh refreshed}.
* @param beanFactory the DefaultListableBeanFactory instance to use for this context
*/
public AnnotationConfigServletWebServerApplicationContext(DefaultListableBeanFactory beanFactory) {
super(beanFactory);
this.reader = new AnnotatedBeanDefinitionReader(this);
this.scanner = new ClassPathBeanDefinitionScanner(this);
}接下来 prepareContext(bootstrapContext, context, environment, listeners, applicationArguments, printedBanner)：
private void prepareContext(ConfigurableApplicationContext context, ConfigurableEnvironment environment, SpringApplicationRunListeners listeners, ApplicationArguments applicationArguments, Banner printedBanner) {
//注入环境属性
context.setEnvironment(environment);
//上下文后置处理
this.postProcessApplicationContext(context);
//完善初始化类的属性
this.applyInitializers(context);
//发送监听事件
listeners.contextPrepared(context);
//日志
if (this.logStartupInfo) {
this.logStartupInfo(context.getParent() == null);
this.logStartupProfileInfo(context);
}
//注册传入的配置参数为bean，这里将传入的参数封装成applicationArguments，内部类似命令行
ConfigurableListableBeanFactory beanFactory = context.getBeanFactory();
beanFactory.registerSingleton("springApplicationArguments", applicationArguments);
//banner打印
if (printedBanner != null) {
beanFactory.registerSingleton("springBootBanner", printedBanner);
}
//这里默认情况下bean定义不允许重复
if (beanFactory instanceof DefaultListableBeanFactory) {
((DefaultListableBeanFactory)beanFactory).setAllowBeanDefinitionOverriding(this.allowBeanDefinitionOverriding);
}
//默认不开启延迟加载
if (this.lazyInitialization) {
context.addBeanFactoryPostProcessor(new LazyInitializationBeanFactoryPostProcessor());
}
//获取全部的资源
//这里获取了启动类的资源和 当前SpringApplication中的source资源。
//到目前来说实际上只有启动类资源
Set<Object> sources = this.getAllSources();
Assert.notEmpty(sources, "Sources must not be empty");
this.load(context, sources.toArray(new Object[0]));
listeners.contextLoaded(context);
}后置处理context
protected void postProcessApplicationContext(ConfigurableApplicationContext context) {
// 是否自定义bean名称生成类
if (this.beanNameGenerator != null) {
context.getBeanFactory().registerSingleton("org.springframework.context.annotation.internalConfigurationBeanNameGenerator", this.beanNameGenerator);
}
//是否指定类加载器
if (this.resourceLoader != null) {
if (context instanceof GenericApplicationContext) {
((GenericApplicationContext)context).setResourceLoader(this.resourceLoader);
}
if (context instanceof DefaultResourceLoader) {
((DefaultResourceLoader)context).setClassLoader(this.resourceLoader.getClassLoader());
}
}
//是否添加数据转换器
//在初始化环境对象的时候也有用到，这里可以直接通过 context.getEnvironment().getConversionService()获取到
if (this.addConversionService) {
context.getBeanFactory().setConversionService(ApplicationConversionService.getSharedInstance());
}
}剩下的都是做一些准备工作。
refreshContext（重点）：
@Override
public void refresh() throws BeansException, IllegalStateException {
synchronized (this.startupShutdownMonitor) {
// Prepare this context for refreshing.
prepareRefresh();
// Tell the subclass to refresh the internal bean factory.
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
// Prepare the bean factory for use in this context.
prepareBeanFactory(beanFactory);
try {
// Allows post-processing of the bean factory in context subclasses.
postProcessBeanFactory(beanFactory);
// Invoke factory processors registered as beans in the context.
invokeBeanFactoryPostProcessors(beanFactory);
// Register bean processors that intercept bean creation.
registerBeanPostProcessors(beanFactory);
// Initialize message source for this context.
initMessageSource();
// Initialize event multicaster for this context.
initApplicationEventMulticaster();
// Initialize other special beans in specific context subclasses.
onRefresh();
// Check for listener beans and register them.
registerListeners();
// Instantiate all remaining (non-lazy-init) singletons.
finishBeanFactoryInitialization(beanFactory);
// Last step: publish corresponding event.
finishRefresh();
}
catch (BeansException ex) {
if (logger.isWarnEnabled()) {
logger.warn("Exception encountered during context initialization - " +
"cancelling refresh attempt: " + ex);
}
// Destroy already created singletons to avoid dangling resources.
destroyBeans();
// Reset 'active' flag.
cancelRefresh(ex);
// Propagate exception to caller.
throw ex;
}
finally {
// Reset common introspection caches in Spring's core, since we
// might not ever need metadata for singleton beans anymore...
resetCommonCaches();
}
}
}首先看prepareRefresh()方法：
@Override
protected void prepareRefresh() {
this.scanner.clearCache();
super.prepareRefresh();
}scnner清了缓存，父类prepareRefresh方法什么都没做；
再看obtainFreshBeanFactory：
protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
refreshBeanFactory();
ConfigurableListableBeanFactory beanFactory = getBeanFactory();
if (logger.isDebugEnabled()) {
logger.debug("Bean factory for " + getDisplayName() + ": " + beanFactory);
}
return beanFactory;
}
@Override
protected final void refreshBeanFactory() throws IllegalStateException {
if (!this.refreshed.compareAndSet(false, true)) {
throw new IllegalStateException(
"GenericApplicationContext does not support multiple refresh attempts: just call 'refresh' once");
}
this.beanFactory.setSerializationId(getId());
}
@Override
public final ConfigurableListableBeanFactory getBeanFactory() {
return this.beanFactory;
}
refreshBeanFactory方法设置了一下id，getBeanFactory方法获取上面创建的factory。
接着看prepareBeanFactory方法：
/**
* Configure the factory's standard context characteristics,
* such as the context's ClassLoader and post-processors.
* @param beanFactory the BeanFactory to configure
*/
protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {
// Tell the internal bean factory to use the context's class loader etc.
beanFactory.setBeanClassLoader(getClassLoader());
if (!shouldIgnoreSpel) {
beanFactory.setBeanExpressionResolver(new StandardBeanExpressionResolver(beanFactory.getBeanClassLoader()));
}
beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, getEnvironment()));
// Configure the bean factory with context callbacks.
beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));
beanFactory.ignoreDependencyInterface(EnvironmentAware.class);
beanFactory.ignoreDependencyInterface(EmbeddedValueResolverAware.class);
beanFactory.ignoreDependencyInterface(ResourceLoaderAware.class);
beanFactory.ignoreDependencyInterface(ApplicationEventPublisherAware.class);
beanFactory.ignoreDependencyInterface(MessageSourceAware.class);
beanFactory.ignoreDependencyInterface(ApplicationContextAware.class);
beanFactory.ignoreDependencyInterface(ApplicationStartupAware.class);
// BeanFactory interface not registered as resolvable type in a plain factory.
// MessageSource registered (and found for autowiring) as a bean.
beanFactory.registerResolvableDependency(BeanFactory.class, beanFactory);
beanFactory.registerResolvableDependency(ResourceLoader.class, this);
beanFactory.registerResolvableDependency(ApplicationEventPublisher.class, this);
beanFactory.registerResolvableDependency(ApplicationContext.class, this);
// Register early post-processor for detecting inner beans as ApplicationListeners.
beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(this));
// Detect a LoadTimeWeaver and prepare for weaving, if found.
if (!NativeDetector.inNativeImage() && beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) {
beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));
// Set a temporary ClassLoader for type matching.
beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
}
// Register default environment beans.
if (!beanFactory.containsLocalBean(ENVIRONMENT_BEAN_NAME)) {
beanFactory.registerSingleton(ENVIRONMENT_BEAN_NAME, getEnvironment());
}
if (!beanFactory.containsLocalBean(SYSTEM_PROPERTIES_BEAN_NAME)) {
beanFactory.registerSingleton(SYSTEM_PROPERTIES_BEAN_NAME, getEnvironment().getSystemProperties());
}
if (!beanFactory.containsLocalBean(SYSTEM_ENVIRONMENT_BEAN_NAME)) {
beanFactory.registerSingleton(SYSTEM_ENVIRONMENT_BEAN_NAME, getEnvironment().getSystemEnvironment());
}
if (!beanFactory.containsLocalBean(APPLICATION_STARTUP_BEAN_NAME)) {
beanFactory.registerSingleton(APPLICATION_STARTUP_BEAN_NAME, getApplicationStartup());
}
}首先忽略一些自动注入；然后增加一些自动注入的依赖（一个接口有多个实现类时，用这里指定的实现类）；然后增加ApplicationListenerDetector的BeanPostProcessor，然后注册一些环境单例bean。
然后再看postProcessBeanFactory：
这是个空方法，由子类实现，当前实现的子类是AnnotationConfigServletWebServerApplicationContext：
@Override
protected void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) {
super.postProcessBeanFactory(beanFactory);
if (this.basePackages != null && this.basePackages.length > 0) {
this.scanner.scan(this.basePackages);
}
if (!this.annotatedClasses.isEmpty()) {
this.reader.register(ClassUtils.toClassArray(this.annotatedClasses));
}
}
/**super.postProcessBeanFactory(beanFactory)：
/**
* Register ServletContextAwareProcessor.
* @see ServletContextAwareProcessor
*/
@Override
protected void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) {
beanFactory.addBeanPostProcessor(new WebApplicationContextServletContextAwareProcessor(this));
beanFactory.ignoreDependencyInterface(ServletContextAware.class);
registerWebApplicationScopes();
}增加了一个后置处理器，忽略自动注入；
再看registerWebApplicationScopes：
/**
* Register web-specific scopes ("request", "session", "globalSession", "application")
* with the given BeanFactory, as used by the WebApplicationContext.
* @param beanFactory the BeanFactory to configure
* @param sc the ServletContext that we're running within
*/
public static void registerWebApplicationScopes(ConfigurableListableBeanFactory beanFactory,
@Nullable ServletContext sc) {
beanFactory.registerScope(WebApplicationContext.SCOPE_REQUEST, new RequestScope());
beanFactory.registerScope(WebApplicationContext.SCOPE_SESSION, new SessionScope());
if (sc != null) {
ServletContextScope appScope = new ServletContextScope(sc);
beanFactory.registerScope(WebApplicationContext.SCOPE_APPLICATION, appScope);
// Register as ServletContext attribute, for ContextCleanupListener to detect it.
sc.setAttribute(ServletContextScope.class.getName(), appScope);
}
beanFactory.registerResolvableDependency(ServletRequest.class, new RequestObjectFactory());
beanFactory.registerResolvableDependency(ServletResponse.class, new ResponseObjectFactory());
beanFactory.registerResolvableDependency(HttpSession.class, new SessionObjectFactory());
beanFactory.registerResolvableDependency(WebRequest.class, new WebRequestObjectFactory());
if (jsfPresent) {
FacesDependencyRegistrar.registerFacesDependencies(beanFactory);
}
}将web请求的几种类型注册；
再回到前面：
if (this.basePackages != null && this.basePackages.length > 0) {
this.scanner.scan(this.basePackages);
}
if (!this.annotatedClasses.isEmpty()) {
this.reader.register(ClassUtils.toClassArray(this.annotatedClasses));
}此处scan不是扫描@ComponentScan指定的包，意义暂不明；
接着看invokeBeanFactoryPostProcessors（重点），注释在代码中.
public static void invokeBeanFactoryPostProcessors(
ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {
// Invoke BeanDefinitionRegistryPostProcessors first, if any.
Set<String> processedBeans = new HashSet<>();
//如果beanFactory是BeanDefinitionRegistry，那先调用beanFactoryPostProcessors中和beanFactory存在的
//类型为BeanDefinitionRegistryPostProcessor的postProcessBeanDefinitionRegistry
//然后调用beanFactoryPostProcessors的postprocessBeanFactory方法
//优先级PriorityOrdered->Ordered->其他
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;
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<>();
// 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);
// 调用DefinitionRegistryPostProcessors
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
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);
}
//然后调用beanFacyory中类型为BeanFactoryPostProcessor的postProcessBeanFactory方法，因为BeanDefinitionRegistryPostProcessor是BeanFactoryPostProcessor的子类
// 所以第一步中处理过的要过滤
// 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();
}查看 invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
/**
* Invoke the given BeanDefinitionRegistryPostProcessor beans.
*/
private static void invokeBeanDefinitionRegistryPostProcessors(
Collection<? extends BeanDefinitionRegistryPostProcessor> postProcessors, BeanDefinitionRegistry registry) {
for (BeanDefinitionRegistryPostProcessor postProcessor : postProcessors) {
// 子类ConfigurationClassPostProcessor实现了自动装配
postProcessor.postProcessBeanDefinitionRegistry(registry);
}
}
/**
* 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);
}
查看processConfigBeanDefinitions
/**
* 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);
}
}
// 找到主类
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 {
// 解析
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();
}
}
进入parse方法:
public void parse(Set<BeanDefinitionHolder> configCandidates) {
for (BeanDefinitionHolder holder : configCandidates) {
BeanDefinition bd = holder.getBeanDefinition();
try {
// 如果是SpringBoot项目进来的，bd其实就是前面主类封装成的 AnnotatedGenericBeanDefinition（AnnotatedBeanDefinition接口的实现类）
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);
}
}
// 加载默认的配置，就是spring.factories里指定的自动装配类---》（对springboot项目来说这里就是自动装配的入口了）
this.deferredImportSelectorHandler.process();
}先看parse(((AnnotatedBeanDefinition) bd).getMetadata(), holder.getBeanName());
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);
}进入doProcessConfigurationClass：
/**
* Apply processing and build a complete {@link ConfigurationClass} by reading the
* annotations, members and methods from the source class. This method can be called
* multiple times as relevant sources are discovered.
* @param configClass the configuration class being build
* @param sourceClass a source class
* @return the superclass, or {@code null} if none found or previously processed
*/
@Nullable
protected final SourceClass doProcessConfigurationClass(ConfigurationClass configClass, SourceClass sourceClass)
throws IOException {
if (configClass.getMetadata().isAnnotated(Component.class.getName())) {
// Recursively process any member (nested) classes first
// 递归处理主类和其内部类，不过主类一般没有内部类
processMemberClasses(configClass, sourceClass);
}
// Process any @PropertySource annotations
// 处理@PropertySource注解
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
// 扫描主类@ComponentScan注解指定的类，如果没有就扫描跟主类在同一个目录下所有类
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
// 处理@Import注解，
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;
}
springboot项目使用了@SpringBootApplication注解，该注解引用了
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@AutoConfigurationPackage
@Import(AutoConfigurationImportSelector.class)
public @interface EnableAutoConfiguration {
可以看到引用了@Import(AutoConfigurationImportSelector.class)，那么上面会将AutoConfigurationImportSelector注册。
接下来回到
public void parse(Set<BeanDefinitionHolder> configCandidates) {
for (BeanDefinitionHolder holder : configCandidates) {
BeanDefinition bd = holder.getBeanDefinition();
try {
// 如果是SpringBoot项目进来的，bd其实就是前面主类封装成的 AnnotatedGenericBeanDefinition（AnnotatedBeanDefinition接口的实现类）
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);
}
}
// 加载默认的配置，就是spring.factories里指定的自动装配类---》（对springboot项目来说这里就是自动装配的入口了）
this.deferredImportSelectorHandler.process();
}看最后一行：
public void process() {
List<DeferredImportSelectorHolder> deferredImports = this.deferredImportSelectors;
this.deferredImportSelectors = null;
try {
if (deferredImports != null) {
DeferredImportSelectorGroupingHandler handler = new DeferredImportSelectorGroupingHandler();
deferredImports.sort(DEFERRED_IMPORT_COMPARATOR);
deferredImports.forEach(handler::register);
handler.processGroupImports();
}
}
finally {
this.deferredImportSelectors = new ArrayList<>();
}
}
public void processGroupImports() {
for (DeferredImportSelectorGrouping grouping : this.groupings.values()) {
// 进入getImports
grouping.getImports().forEach(entry -> {
ConfigurationClass configurationClass = this.configurationClasses.get(
entry.getMetadata());
try {
processImports(configurationClass, asSourceClass(configurationClass),
asSourceClasses(entry.getImportClassName()), false);
}
catch (BeanDefinitionStoreException ex) {
throw ex;
}
catch (Throwable ex) {
throw new BeanDefinitionStoreException(
"Failed to process import candidates for configuration class [" +
configurationClass.getMetadata().getClassName() + "]", ex);
}
});
}
}
/**
* Return the imports defined by the group.
* @return each import with its associated configuration class
*/
public Iterable<Group.Entry> getImports() {
for (DeferredImportSelectorHolder deferredImport : this.deferredImports) {
// 处理@import
this.group.process(deferredImport.getConfigurationClass().getMetadata(),
deferredImport.getImportSelector());
}
return this.group.selectImports();
}查看this.group.process方法：
@Override
public void process(AnnotationMetadata annotationMetadata, DeferredImportSelector deferredImportSelector) {
Assert.state(deferredImportSelector instanceof AutoConfigurationImportSelector,
() -> String.format("Only %s implementations are supported, got %s",
AutoConfigurationImportSelector.class.getSimpleName(),
deferredImportSelector.getClass().getName()));
// 这里就是获取自动装配类的源码了，此处的deferredImportSelector就是@SpringBootApplication注解导入的AutoConfigurationImportSelector
AutoConfigurationEntry autoConfigurationEntry =
((AutoConfigurationImportSelector) deferredImportSelector)
.getAutoConfigurationEntry(annotationMetadata);
this.autoConfigurationEntries.add(autoConfigurationEntry);
for (String importClassName : autoConfigurationEntry.getConfigurations()) {
this.entries.putIfAbsent(importClassName, annotationMetadata);
}
} protected AutoConfigurationEntry getAutoConfigurationEntry(AnnotationMetadata annotationMetadata) {
if (!isEnabled(annotationMetadata)) {
return EMPTY_ENTRY;
}
// 获取主类注解上的exclude
AnnotationAttributes attributes = getAttributes(annotationMetadata);
// 获取所有自动装配类
List<String> configurations = getCandidateConfigurations(annotationMetadata, attributes);
// 处理重复类
configurations = removeDuplicates(configurations);
// 处理exclude
Set<String> exclusions = getExclusions(annotationMetadata, attributes);
checkExcludedClasses(configurations, exclusions);
configurations.removeAll(exclusions);
// condition过滤
configurations = getConfigurationClassFilter().filter(configurations);
fireAutoConfigurationImportEvents(configurations, exclusions);
return new AutoConfigurationEntry(configurations, exclusions);
} /**
* Return the auto-configuration class names that should be considered. By default
* this method will load candidates using {@link ImportCandidates} with
* {@link #getSpringFactoriesLoaderFactoryClass()}. For backward compatible reasons it
* will also consider {@link SpringFactoriesLoader} with
* {@link #getSpringFactoriesLoaderFactoryClass()}.
* @param metadata the source metadata
* @param attributes the {@link #getAttributes(AnnotationMetadata) annotation
* attributes}
* @return a list of candidate configurations
*/
protected List<String> getCandidateConfigurations(AnnotationMetadata metadata, AnnotationAttributes attributes) {
//getSpringFactoriesLoaderFactoryClass方法返回EnableAutoConfiguration.class，就是代表自动装配类
//SpringFactoriesLoader.loadFactoryNames方法注册spring.factories里所有org.springframework.boot.autoconfigure.EnableAutoConfiguration指定的类
List<String> configurations = new ArrayList<>(
SpringFactoriesLoader.loadFactoryNames(getSpringFactoriesLoaderFactoryClass(), getBeanClassLoader()));
// 注册路径下META-INF/spring/full-qualified-annotation-name.imports的类
ImportCandidates.load(AutoConfiguration.class, getBeanClassLoader()).forEach(configurations::add);
Assert.notEmpty(configurations,
"No auto configuration classes found in META-INF/spring.factories nor in META-INF/spring/org.springframework.boot.autoconfigure.AutoConfiguration.imports. If you "
+ "are using a custom packaging, make sure that file is correct.");
return configurations;
} /**
* Return the class used by {@link SpringFactoriesLoader} to load configuration
* candidates.
* @return the factory class
*/
protected Class<?> getSpringFactoriesLoaderFactoryClass() {
return EnableAutoConfiguration.class;
}
public static List<String> loadFactoryNames(Class<?> factoryType, @Nullable ClassLoader classLoader) {
ClassLoader classLoaderToUse = classLoader;
if (classLoaderToUse == null) {
classLoaderToUse = SpringFactoriesLoader.class.getClassLoader();
}
String factoryTypeName = factoryType.getName();
return loadSpringFactories(classLoaderToUse).getOrDefault(factoryTypeName, Collections.emptyList());
}
private static Map<String, List<String>> loadSpringFactories(ClassLoader classLoader) {
Map<String, List<String>> result = cache.get(classLoader);
if (result != null) {
return result;
}
result = new HashMap<>();
try {
// public static final String FACTORIES_RESOURCE_LOCATION = "META-INF/spring.factories";
Enumeration<URL> urls = classLoader.getResources(FACTORIES_RESOURCE_LOCATION);
while (urls.hasMoreElements()) {
URL url = urls.nextElement();
UrlResource resource = new UrlResource(url);
Properties properties = PropertiesLoaderUtils.loadProperties(resource);
for (Map.Entry<?, ?> entry : properties.entrySet()) {
String factoryTypeName = ((String) entry.getKey()).trim();
String[] factoryImplementationNames =
StringUtils.commaDelimitedListToStringArray((String) entry.getValue());
for (String factoryImplementationName : factoryImplementationNames) {
result.computeIfAbsent(factoryTypeName, key -> new ArrayList<>())
.add(factoryImplementationName.trim());
}
}
}
// Replace all lists with unmodifiable lists containing unique elements
result.replaceAll((factoryType, implementations) -> implementations.stream().distinct()
.collect(Collectors.collectingAndThen(Collectors.toList(), Collections::unmodifiableList)));
cache.put(classLoader, result);
}
catch (IOException ex) {
throw new IllegalArgumentException("Unable to load factories from location [" +
FACTORIES_RESOURCE_LOCATION + "]", ex);
}
return result;
}
这样，所有的自动装配类都被注册进了spring容器。
invokeBeanFactoryPostProcessors方法结束，接着看registerBeanPostProcessors：
/*
Register bean processors that intercept bean creation.
注册BeanPostProcessor（Bean的后置处理器），在创建bean的前后等执行
*/
public static void registerBeanPostProcessors(
ConfigurableListableBeanFactory beanFactory, AbstractApplicationContext applicationContext) {
//获取所有postProcessor的名称
String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanPostProcessor.class, true, false);
// Register BeanPostProcessorChecker that logs an info message when
// a bean is created during BeanPostProcessor instantiation, i.e. when
// a bean is not eligible for getting processed by all BeanPostProcessors.
int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length;
beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));
// Separate between BeanPostProcessors that implement PriorityOrdered,
// Ordered, and the rest.
List<BeanPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
//存储PriorityOrdered.class的postProcessor
List<BeanPostProcessor> internalPostProcessors = new ArrayList<>();
//存储Ordered.class的postProcessor
List<String> orderedPostProcessorNames = new ArrayList<>();
//存储其他的postProcessor
List<String> nonOrderedPostProcessorNames = new ArrayList<>();
for (String ppName : postProcessorNames) {
//优先级最高
if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
priorityOrderedPostProcessors.add(pp);
if (pp instanceof MergedBeanDefinitionPostProcessor) {
internalPostProcessors.add(pp);
}
}
//优先级第二
else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
orderedPostProcessorNames.add(ppName);
}
else {
//优先级最末
nonOrderedPostProcessorNames.add(ppName);
}
}
// First, register the BeanPostProcessors that implement PriorityOrdered.
sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
//注册PriorityOrdered.class的BeanPostProcessors，所谓注册就是内部的List<BeanPostProcessor> beanPostProcessors对象加上这个BeanPostProcessor
//在这之前这个bean只作为一个普通bean存在于beanFactory
registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);
// Next, register the BeanPostProcessors that implement Ordered.
//注册Ordered.class的BeanPostProcessors，
List<BeanPostProcessor> orderedPostProcessors = new ArrayList<>();
for (String ppName : orderedPostProcessorNames) {
BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
orderedPostProcessors.add(pp);
if (pp instanceof MergedBeanDefinitionPostProcessor) {
internalPostProcessors.add(pp);
}
}
sortPostProcessors(orderedPostProcessors, beanFactory);
registerBeanPostProcessors(beanFactory, orderedPostProcessors);
// Now, register all regular BeanPostProcessors.
List<BeanPostProcessor> nonOrderedPostProcessors = new ArrayList<>();
for (String ppName : nonOrderedPostProcessorNames) {
BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
nonOrderedPostProcessors.add(pp);
if (pp instanceof MergedBeanDefinitionPostProcessor) {
internalPostProcessors.add(pp);
}
}
registerBeanPostProcessors(beanFactory, nonOrderedPostProcessors);
// Finally, re-register all internal BeanPostProcessors.
//注册其他的BeanPostProcessors，
sortPostProcessors(internalPostProcessors, beanFactory);
registerBeanPostProcessors(beanFactory, internalPostProcessors);
// Re-register post-processor for detecting inner beans as ApplicationListeners,
// moving it to the end of the processor chain (for picking up proxies etc).
beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext));
}
下面是initMessageSource，不是重点，先不看
/*
Initialize message source for this context.
初始化MessageSource组件（做国际化功能；消息绑定，消息解析）；
*/
initMessageSource();
initApplicationEventMulticaster也不是重点，先不看
/*
Initialize event multicaster for this context.
初始化事件派发器
*/
initApplicationEventMulticaster();onFresh，空方法，交给子类实现
/*
Initialize other special beans in specific context subclasses.
子类重写这个方法，在容器刷新的时候可以自定义逻辑；如创建Tomcat，Jetty等WEB服务器
*/
onRefresh();
registerListener，先不看
/*
Check for listener beans and register them.
注册应用的监听器。就是注册实现了ApplicationListener接口的监听器bean
*/
registerListeners();finishBeanFactoryInitialization（重点）：
/*
Instantiate all remaining (non-lazy-init) singletons.
初始化所有剩下的非懒加载的单例bean
初始化创建非懒加载方式的单例Bean实例（未设置属性）
填充属性
初始化方法调用（比如调用afterPropertiesSet方法、init-method方法）
调用BeanPostProcessor（后置处理器）对实例bean进行后置处理
*/
finishBeanFactoryInitialization(beanFactory);
/**
* Finish the initialization of this context's bean factory,
* initializing all remaining singleton beans.
* 结束 bean factory 的初始化工作
* 实例化所有单例bean
*/
protected void finishBeanFactoryInitialization(ConfigurableListableBeanFactory beanFactory) {
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));
}
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.
// 实例化所有立即加载的单例bean
beanFactory.preInstantiateSingletons();
}
@Override
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.
// 所有bean的名字
List<String> beanNames = new ArrayList<>(this.beanDefinitionNames);
// Trigger initialization of all non-lazy singleton beans...
// 触发所有非延迟加载单例bean的初始化，主要步骤为getBean
for (String beanName : beanNames) {
// 合并父BeanDefinition对象
// map.get(beanName)
RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName);
if (!bd.isAbstract() && bd.isSingleton() && !bd.isLazyInit()) {
if (isFactoryBean(beanName)) {
Object bean = getBean(FACTORY_BEAN_PREFIX + beanName);
// 如果是FactoryBean则加&
if (bean instanceof FactoryBean) {
final 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());
}
if (isEagerInit) {
getBean(beanName);
}
}
}
else {
// 实例化当前bean
getBean(beanName);
}
}
}
// Trigger post-initialization callback for all applicable beans...
for (String beanName : beanNames) {
Object singletonInstance = getSingleton(beanName);
if (singletonInstance instanceof SmartInitializingSingleton) {
final SmartInitializingSingleton smartSingleton = (SmartInitializingSingleton) singletonInstance;
if (System.getSecurityManager() != null) {
AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
smartSingleton.afterSingletonsInstantiated();
return null;
}, getAccessControlContext());
}
else {
smartSingleton.afterSingletonsInstantiated();
}
}
}
}
看getBean方法，调用的是org.springframework.beans.factory.support.AbstractBeanFactory#getBean(java.lang.String)：
@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(final String name, @Nullable final Class<T> requiredType,
@Nullable final Object[] args, boolean typeCheckOnly) throws BeansException {
// 解析beanName 如果以&开头去掉&开头，如果是别名获取到真正的名字
final String beanName = transformedBeanName(name);
Object bean;
// 单纯理解尝试从缓存中获取 bean
Object sharedInstance = getSingleton(beanName);
// 如果已经存在则返回
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 + "'");
}
}
// 针对 FactoryBean 的处理
bean = getObjectForBeanInstance(sharedInstance, name, beanName, null);
}
else {
// 如果是prototype类型且开启允许循环依赖，则抛出异常
if (isPrototypeCurrentlyInCreation(beanName)) {
throw new BeanCurrentlyInCreationException(beanName);
}
// Check if bean definition exists in this factory.
// 检查父工厂中是否存在该对象
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 {
// 合并父子bean 属性
final RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
checkMergedBeanDefinition(mbd, beanName, args);
// Guarantee initialization of beans that the current bean depends on.
// 处理dependsOn配置
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);
}
}
}
// 创建单例bean
if (mbd.isSingleton()) {
sharedInstance = getSingleton(beanName, () -> {
try {
// 创建 bean
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);
}
bean = getObjectForBeanInstance(prototypeInstance, name, beanName, mbd);
}
else {
String scopeName = mbd.getScope();
final 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;
}
先从缓存中获取：
// 单纯理解尝试从缓存中获取 bean
Object sharedInstance = getSingleton(beanName);
/**
* Return the (raw) singleton object registered under the given name.
* <p>Checks already instantiated singletons and also allows for an early
* reference to a currently created singleton (resolving a circular reference).
* @param beanName the name of the bean to look for
* @param allowEarlyReference whether early references should be created or not
* @return the registered singleton object, or {@code null} if none found
*/
@Nullable
protected Object getSingleton(String beanName, boolean allowEarlyReference) {
Object singletonObject = this.singletonObjects.get(beanName);
if (singletonObject == null && isSingletonCurrentlyInCreation(beanName)) {
synchronized (this.singletonObjects) {
singletonObject = this.earlySingletonObjects.get(beanName);
if (singletonObject == null && allowEarlyReference) {
ObjectFactory<?> singletonFactory = this.singletonFactories.get(beanName);
if (singletonFactory != null) {
singletonObject = singletonFactory.getObject();
this.earlySingletonObjects.put(beanName, singletonObject);
this.singletonFactories.remove(beanName);
}
}
}
}
return singletonObject;
}这里用到了三级缓存，一级一级获取，如果从三级缓存获取到了则放入二级缓存，从三级缓存移除。
如果获取不到，则调用getSingleton方法：
// 创建单例bean
if (mbd.isSingleton()) {
sharedInstance = getSingleton(beanName, () -> {
try {
// 创建 bean
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);
}
/**
* Return the (raw) singleton object registered under the given name,
* creating and registering a new one if none registered yet.
* @param beanName the name of the bean
* @param singletonFactory the ObjectFactory to lazily create the singleton
* with, if necessary
* @return the registered singleton object
*/
public Object getSingleton(String beanName, ObjectFactory<?> singletonFactory) {
Assert.notNull(beanName, "Bean name must not be null");
synchronized (this.singletonObjects) {
Object singletonObject = this.singletonObjects.get(beanName);
if (singletonObject == null) {
// 是否正在销毁，异常
if (this.singletonsCurrentlyInDestruction) {
throw new BeanCreationNotAllowedException(beanName,
"Singleton bean creation not allowed while singletons of this factory are in destruction " +
"(Do not request a bean from a BeanFactory in a destroy method implementation!)");
}
if (logger.isDebugEnabled()) {
logger.debug("Creating shared instance of singleton bean '" + beanName + "'");
}
// 验证完要真正开始创建对象，先标识该bean正在被创建，因为spingbean创建过程复杂，步骤很多，需要标识
beforeSingletonCreation(beanName);
boolean newSingleton = false;
boolean recordSuppressedExceptions = (this.suppressedExceptions == null);
if (recordSuppressedExceptions) {
this.suppressedExceptions = new LinkedHashSet<>();
}
try {
// 传进来的调用，lamda表达式使用
singletonObject = singletonFactory.getObject();
newSingleton = true;
}
catch (IllegalStateException ex) {
// Has the singleton object implicitly appeared in the meantime ->
// if yes, proceed with it since the exception indicates that state.
singletonObject = this.singletonObjects.get(beanName);
if (singletonObject == null) {
throw ex;
}
}
catch (BeanCreationException ex) {
if (recordSuppressedExceptions) {
for (Exception suppressedException : this.suppressedExceptions) {
ex.addRelatedCause(suppressedException);
}
}
throw ex;
}
finally {
if (recordSuppressedExceptions) {
this.suppressedExceptions = null;
}
afterSingletonCreation(beanName);
}
if (newSingleton) {
addSingleton(beanName, singletonObject);
}
}
return singletonObject;
}
}
看看 singletonFactory.getObject()方法，也就是传参的lamda表达式的createBean（）方法：
// 传进来的调用，lamda表达式使用
singletonObject = singletonFactory.getObject();
/**
* 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 + "'");
}
// 拿到Bd
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.
// 获得类信息
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 {
// 进入，真真正正创建bean
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);
}
}
进入doCreateBean：
/**
* 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(final String beanName, final RootBeanDefinition mbd, final @Nullable Object[] args)
throws BeanCreationException {
// Instantiate the bean.
BeanWrapper instanceWrapper = null;
if (mbd.isSingleton()) {
instanceWrapper = this.factoryBeanInstanceCache.remove(beanName);
}
if (instanceWrapper == null) {
// 创建 Bean 实例，仅仅调用构造方法，但是尚未设置属性
instanceWrapper = createBeanInstance(beanName, mbd, args);
}
final 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));
//放入三级缓存中
if (earlySingletonExposure) {
if (logger.isTraceEnabled()) {
logger.trace("Eagerly caching bean '" + beanName +
"' to allow for resolving potential circular references");
}
addSingletonFactory(beanName, () -> getEarlyBeanReference(beanName, mbd, bean));
}
// 初始化bean实例
Object exposedObject = bean;
try {
// Bean属性填充
populateBean(beanName, mbd, instanceWrapper);
// 调用初始化方法，应用BeanPostProcessor后置处理器
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 " +
"'getBeanNamesOfType' 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;
}
查看populateBean方法：
/**
* Populate the bean instance in the given BeanWrapper with the property values
* from the bean definition.
* @param beanName the name of the bean
* @param mbd the bean definition for the bean
* @param bw the BeanWrapper with bean instance
*/
@SuppressWarnings("deprecation") // for postProcessPropertyValues
protected void populateBean(String beanName, RootBeanDefinition mbd, @Nullable BeanWrapper bw) {
if (bw == null) {
if (mbd.hasPropertyValues()) {
throw new BeanCreationException(
mbd.getResourceDescription(), beanName, "Cannot apply property values to null instance");
}
else {
// Skip property population phase for null instance.
return;
}
}
// Give any InstantiationAwareBeanPostProcessors the opportunity to modify the
// state of the bean before properties are set. This can be used, for example,
// to support styles of field injection.
if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) {
for (BeanPostProcessor bp : getBeanPostProcessors()) {
if (bp instanceof InstantiationAwareBeanPostProcessor) {
InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
if (!ibp.postProcessAfterInstantiation(bw.getWrappedInstance(), beanName)) {
return;
}
}
}
}
PropertyValues pvs = (mbd.hasPropertyValues() ? mbd.getPropertyValues() : null);
int resolvedAutowireMode = mbd.getResolvedAutowireMode();
if (resolvedAutowireMode == AUTOWIRE_BY_NAME || resolvedAutowireMode == AUTOWIRE_BY_TYPE) {
MutablePropertyValues newPvs = new MutablePropertyValues(pvs);
// Add property values based on autowire by name if applicable.
if (resolvedAutowireMode == AUTOWIRE_BY_NAME) {
autowireByName(beanName, mbd, bw, newPvs);
}
// Add property values based on autowire by type if applicable.
if (resolvedAutowireMode == AUTOWIRE_BY_TYPE) {
autowireByType(beanName, mbd, bw, newPvs);
}
pvs = newPvs;
}
boolean hasInstAwareBpps = hasInstantiationAwareBeanPostProcessors();
boolean needsDepCheck = (mbd.getDependencyCheck() != AbstractBeanDefinition.DEPENDENCY_CHECK_NONE);
PropertyDescriptor[] filteredPds = null;
if (hasInstAwareBpps) {
if (pvs == null) {
pvs = mbd.getPropertyValues();
}
for (BeanPostProcessor bp : getBeanPostProcessors()) {
if (bp instanceof InstantiationAwareBeanPostProcessor) {
InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
PropertyValues pvsToUse = ibp.postProcessProperties(pvs, bw.getWrappedInstance(), beanName);
if (pvsToUse == null) {
if (filteredPds == null) {
filteredPds = filterPropertyDescriptorsForDependencyCheck(bw, mbd.allowCaching);
}
pvsToUse = ibp.postProcessPropertyValues(pvs, filteredPds, bw.getWrappedInstance(), beanName);
if (pvsToUse == null) {
return;
}
}
pvs = pvsToUse;
}
}
}
if (needsDepCheck) {
if (filteredPds == null) {
filteredPds = filterPropertyDescriptorsForDependencyCheck(bw, mbd.allowCaching);
}
checkDependencies(beanName, mbd, filteredPds, pvs);
}
if (pvs != null) {
applyPropertyValues(beanName, mbd, bw, pvs);
}
}
一直到DependencyDescriptor的resolveCandidate方法
resolveCandidate:276, DependencyDescriptor (org.springframework.beans.factory.config)
doResolveDependency:1391, DefaultListableBeanFactory (org.springframework.beans.factory.support)
resolveDependency:1311, DefaultListableBeanFactory (org.springframework.beans.factory.support)
resolveFieldValue:656, AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement (org.springframework.beans.factory.annotation)
inject:639, AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement (org.springframework.beans.factory.annotation)
inject:119, InjectionMetadata (org.springframework.beans.factory.annotation)
postProcessProperties:399, AutowiredAnnotationBeanPostProcessor (org.springframework.beans.factory.annotation)
populateBean:1431, AbstractAutowireCapableBeanFactory /**
* Resolve the specified bean name, as a candidate result of the matching
* algorithm for this dependency, to a bean instance from the given factory.
* <p>The default implementation calls {@link BeanFactory#getBean(String)}.
* Subclasses may provide additional arguments or other customizations.
* @param beanName the bean name, as a candidate result for this dependency
* @param requiredType the expected type of the bean (as an assertion)
* @param beanFactory the associated factory
* @return the bean instance (never {@code null})
* @throws BeansException if the bean could not be obtained
* @since 4.3.2
* @see BeanFactory#getBean(String)
*/
public Object resolveCandidate(String beanName, Class<?> requiredType, BeanFactory beanFactory)
throws BeansException {
return beanFactory.getBean(beanName);
}
又调了一次getBean去获取引用的bean，如果此bean也引用了上面的bean会怎么样？设第一次实例化的bean为A，A引用B,B同时引用A，A填充属性B的时候发现B没有实例化，就会去实例化B，B填充属性A的时候去缓存拿，由于A已经放到三级缓存了，那么就会拿出A，把A从三级缓存删除，放到二级缓存中，这样B就实例化好了，B实例化好后会把自己放入以及缓存，从二级和三级缓存删除，然后回到A的流程，A填充完B，这样A也实例化好了。
为什么需要三级缓存，个人觉得一级其实也够用，不过一级的缓存中可能会有为填充属性的bean，这样spring某些地方获取到可能有问题，那么至少要两级，一级放完全实例化好的，二级放未填充属性的，第三级的作用是因为有些bean可能会需要被代理，A引用B，这个B应该是个代理类，所以需要第三级缓存来把B变成代理类：
if (earlySingletonExposure) {
if (logger.isTraceEnabled()) {
logger.trace("Eagerly caching bean '" + beanName +
"' to allow for resolving potential circular references");
}
addSingletonFactory(beanName, () -> getEarlyBeanReference(beanName, mbd, bean));
} /**
* Obtain a reference for early access to the specified bean,
* typically for the purpose of resolving a circular reference.
* @param beanName the name of the bean (for error handling purposes)
* @param mbd the merged bean definition for the bean
* @param bean the raw bean instance
* @return the object to expose as bean reference
*/
protected Object getEarlyBeanReference(String beanName, RootBeanDefinition mbd, Object bean) {
Object exposedObject = bean;
if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) {
for (SmartInstantiationAwareBeanPostProcessor bp : getBeanPostProcessorCache().smartInstantiationAware) {
exposedObject = bp.getEarlyBeanReference(exposedObject, beanName);
}
}
return exposedObject;
}
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