ignoreDependencyInterface(Class<?> ifc);
/**
* Ignore the given dependency interface for autowiring.
* <p>This will typically be used by application contexts to register
* dependencies that are resolved in other ways, like BeanFactory through
* BeanFactoryAware or ApplicationContext through ApplicationContextAware.
* <p>By default, only the BeanFactoryAware interface is ignored.
* For further types to ignore, invoke this method for each type.
* @param ifc the dependency interface to ignore
* @see org.springframework.beans.factory.BeanFactoryAware
* @see org.springframework.context.ApplicationContextAware
*/
- 忽略自动装配的给定依赖接口。
- 这通常会被应用上下文用来注册。
- 通过其他方式解析的依赖，比如通过BeanFactory。
- BeanFactoryAware或通过ApplicationContextAware实现ApplicationContext。
- 默认情况下，只有BeanFactoryAware接口被忽略。
- 如果要忽略其他类型，请对每种类型都调用此方法。
- @param ifc要忽略的依赖接口。
讲白点，他到底是干啥的？其实他是来忽略某个接口的，我们都知道spring是基于JDK的动态代理实现的，而JDK的动态代理的实现是基于接口形式来做的。那么你忽略了接口，也就是相当于该接口下的所有的子实现，在spring容器进行初始化的时候都会被忽略，也就是不会被注入到spring-context中。
ok，下面我们看例子：
public interface X {
public void setY(Y y);
}
@Component
public class Y {
}
@Slf4j(topic = "spring-studentsss")
@Component
public class W implements X {
Y y;
@Override
public void setY(Y y) {
this.y = y;
printInfo(y);
}
public void printInfo(Y y) {
System.out.println("当前的y是否被注入进来了?" + y);
}
}
@Component
public class TestIgnoreDependencyInterface implements BeanFactoryPostProcessor {
@Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
ScannedGenericBeanDefinition m = (ScannedGenericBeanDefinition) beanFactory.getBeanDefinition("w");
//设置自动注入模型
m.setAutowireMode(AbstractBeanDefinition.AUTOWIRE_BY_TYPE);
}
}
@Slf4j(topic = "e:")
@Configuration
@ComponentScan("com.lukp.beanFactoryPostProcessor")
public class TestBeanFactoryPostProcessor {
public static void main(String[] args) {
AnnotationConfigApplicationContext ioc = new AnnotationConfigApplicationContext(TestBeanFactoryPostProcessor.class);
ioc.getBean(W.class);
}
}
理解一下上面的这些代码：
- 首先我们有一个接口X，该接口中有一个方法 setY();
- 再看还有一个并未实现接口X的Y，那么当接口X被忽略的时候，他也还是会被注入到spring-context中。
- 还有以一个W他实现了接口X，并且在内部的代码中会去实现接口X的方法setY()，并且在类中定义了一个属性Y，注意他上面是没有使用类似于@Autowrite或者是@Resoure这样的DI注解。
- 这里我们在TestIgnoreDependencyInterface类中实现了BeanFactoryProcessor接口，并且重写了他的方法postProcessBeanFactory()，在方法内部我们获取到了在主启动类中要获取的W这个Bean，并且我们设置W这个Bean的Beandefinition中的DI模型为TYPE。
- 然后再看主启动类，他要的W这个Bean。
- 好的，我们现在启动程序，最后会发现是可以拿到这个W这个bean的。
��ǰ��y�Ƿ�ע�������?com.lukp.beanFactoryPostProcessor.ignoreDependecyInterface.Y@341b80b2
- 那么我现在要在实现beanFactoryProcessor接口的方法中加上一行代码：beanFactory.ignoreDependencyInterface(X.class);
@Component
public class TestIgnoreDependencyInterface implements BeanFactoryPostProcessor {
@Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
ScannedGenericBeanDefinition m = (ScannedGenericBeanDefinition) beanFactory.getBeanDefinition("w");
//设置自动注入模型
m.setAutowireMode(AbstractBeanDefinition.AUTOWIRE_BY_TYPE);
//设置在自动注入时被忽略的interface
beanFactory.ignoreDependencyInterface(X.class);
}
}
- 再次运行程序你会发现，y这个bean并没输出。
ok，上述代码的测试就到这里结束了，但是我们总会是有疑问的，好端端的spring为什么要暴露这个开口或者说这个扩展点给我们呢？
- 这解释起来较长，我现在先看一下spring中用到ignoreDependencyInterface(Class<?> ifc);方法的。
- 我现在进到大名鼎鼎的refresh();方法中。
- 然后再进入到prepareBeanFactory(beanFactory);方法中(该方法的作用：Prepare the bean factory for use in this context.)
protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {
// Tell the internal bean factory to use the context's class loader etc.
beanFactory.setBeanClassLoader(getClassLoader());
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 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 (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());
}
}
- 可以看到再9到14行都是ignoreDependencyInterface(Class<?> ifc);方法调用。
- 好的我们来做一下解释这个ignoreDependencyInterface(Class<?> ifc);方法到底在spring生态中起到什么样的作用。
- 这里就抽出其中的一行来进行说明即可因为道理都是一样的，比如我们就说beanFactory.ignoreDependencyInterface(ResourceLoaderAware.class);这行代码：
- 要知道ignoreDependencyInterface(Class ifc);方法忽略的是接口，那么ignoreDependencyInterface(Class ifc);中的参数填的必定是某个接口，其实没有错就是ResourceLoaderAware.class他就是一个接口，并且他里面有一个接口方法void setResourceLoader(ResourceLoader resourceLoader);可以看一下源码：
public interface ResourceLoaderAware extends Aware {
/**
* Set the ResourceLoader that this object runs in.
* <p>This might be a ResourcePatternResolver, which can be checked
* through {@code instanceof ResourcePatternResolver}. See also the
* {@code ResourcePatternUtils.getResourcePatternResolver} method.
* <p>Invoked after population of normal bean properties but before an init callback
* like InitializingBean's {@code afterPropertiesSet} or a custom init-method.
* Invoked before ApplicationContextAware's {@code setApplicationContext}.
* @param resourceLoader the ResourceLoader object to be used by this object
* @see org.springframework.core.io.support.ResourcePatternResolver
* @see org.springframework.core.io.support.ResourcePatternUtils#getResourcePatternResolver
*/
void setResourceLoader(ResourceLoader resourceLoader);
}
- 结合上面的例子来说：
-
- 首先是不是所有实现了ResourceLoaderAware接口的方法都会去实现setResourceLoader方法并且会传入一个ResourceLoader对象。
- 那么现在prepareBeanFactory(ConfigurableListableBeanFactory beanFactory)方法中将这个接口忽略了，是不是就说明了，ResourceLoaderAware接口的实现子类，想要注入ResourceLoader对象都会失败。
- 注意：这里所说的注入的对象必须是自动注入才算。
- 其他的我就不一样来看了。事情发展到这里，我们还不能完全解释清楚spring到底为什么要有一个忽略interface的扩展点。
- ok，到这里我们先别管这个事情，先回头来观察一下你会发现在prepareBeanFactory方法中的那些被忽略的接口是不是都叫什么Aware为后缀，并且进入了接口的内部也会发现，他都统一实现了一个接口Aware。
public interface EnvironmentAware extends Aware
public interface EmbeddedValueResolverAware extends Aware
public interface ResourceLoaderAware extends Aware
public interface ApplicationEventPublisherAware extends Aware
public interface MessageSourceAware extends Aware
public interface ApplicationContextAware extends Aware
- 并且这些接口是不是都有一个set()方法！ 具体每个接口中的set()方法我就不贴图了。
- 下面我们来简洁的说一下Aware接口的作用：
- 首先我们要分清楚很重要的一点，Spring中Bean和BeanFactory的初始化过程是不一样的。我们现在聊的是SpringBeanFactory的初始化过程。
- 在BeanFactory初始化的过程中，他会为每一个Bean都开辟一条声明周期。
- 每个Bean的生命周期都是分为好几步，经过好几步来把Bean创建出来，例如：
-
- 先获取BeanDefinition，再对BeanDefinition进行验证，然后对构造器进行推断，合并AOP等等步骤。
- 在这里我们不管他是怎么样的，但是当一个Bean被BeanFactory实例化出来的之前他是肯定要做一个Aware的操作的，获取说要看一下当前实例化的这个Bean有没有要实现某个Aware接口。
- 比如我们现在实现了ApplicationContextAware接口，那就要实现setApplicationContext()方法，他就会在该方法中把ApplicationContext对象传个你。
@Slf4j(topic = "spring-student:")
@Component
public class Z implements ApplicationContextAware {
ApplicationContext applicationContext;
@Override
public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
this.applicationContext = applicationContext;
log.debug("applicationContext-name:{}", applicationContext.getClass().getSimpleName());
log.debug("当前spring容器中已经有了,你在可以在你的Z中随意使用~~~");
}
}
public interface ApplicationContextAware extends Aware {
/**
* Set the ApplicationContext that this object runs in.
* Normally this call will be used to initialize the object.
* <p>Invoked after population of normal bean properties but before an init callback such
* as {@link org.springframework.beans.factory.InitializingBean#afterPropertiesSet()}
* or a custom init-method. Invoked after {@link ResourceLoaderAware#setResourceLoader},
* {@link ApplicationEventPublisherAware#setApplicationEventPublisher} and
* {@link MessageSourceAware}, if applicable.
* @param applicationContext the ApplicationContext object to be used by this object
* @throws ApplicationContextException in case of context initialization errors
* @throws BeansException if thrown by application context methods
* @see org.springframework.beans.factory.BeanInitializationException
*/
void setApplicationContext(ApplicationContext applicationContext) throws BeansException;
}
- 下面是详细的执行Aware接口的流程：
@Slf4j(topic = "e:")
@Configuration
@ComponentScan("com.lukp.beanFactoryPostProcessor")
public class TestBeanFactoryPostProcessor {
public static void main(String[] args) {
AnnotationConfigApplicationContext ioc = new AnnotationConfigApplicationContext(TestBeanFactoryPostProcessor.class);
ioc.getBean(W.class);
}
}
public AnnotationConfigApplicationContext(Class<?>... componentClasses) {
this();
//配置类的注册---other
register(componentClasses);
//该方法就是spring的初始化过程
refresh();
}
@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();
}
}
}
protected void finishBeanFactoryInitialization(ConfigurableListableBeanFactory beanFactory) {
// Initialize conversion service for this context.
if (beanFactory.containsBean(CONVERSION_SERVICE_BEAN_NAME) && beanFactory.isTypeMatch(CONVERSION_SERVICE_BEAN_NAME, ConversionService.class)) {
beanFactory.setConversionService(beanFactory.getBean(CONVERSION_SERVICE_BEAN_NAME, ConversionService.class));
}
// Register a default embedded value resolver if no BeanFactoryPostProcessor
// (such as a PropertySourcesPlaceholderConfigurer bean) registered any before:
// at this point, primarily for resolution in annotation attribute values.
if (!beanFactory.hasEmbeddedValueResolver()) {
beanFactory.addEmbeddedValueResolver(strVal -> getEnvironment().resolvePlaceholders(strVal));
}
// Initialize LoadTimeWeaverAware beans early to allow for registering their transformers early.
String[] weaverAwareNames = beanFactory.getBeanNamesForType(LoadTimeWeaverAware.class, false, false);
for (String weaverAwareName : weaverAwareNames) {
getBean(weaverAwareName);
}
// Stop using the temporary ClassLoader for type matching.
beanFactory.setTempClassLoader(null);
// Allow for caching all bean definition metadata, not expecting further changes.
beanFactory.freezeConfiguration();
// Instantiate all remaining (non-lazy-init) singletons.
beanFactory.preInstantiateSingletons();
}
public void preInstantiateSingletons() throws BeansException {
if (logger.isTraceEnabled()) {
logger.trace("Pre-instantiating singletons in " + this);
}
// Iterate over a copy to allow for init methods which in turn register new bean definitions.
// While this may not be part of the regular factory bootstrap, it does otherwise work fine.
List<String> beanNames = new ArrayList<>(this.beanDefinitionNames);
// Trigger initialization of all non-lazy singleton beans...
for (String beanName : beanNames) {
RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName);
if (!bd.isAbstract() && bd.isSingleton() && !bd.isLazyInit()) {
if (isFactoryBean(beanName)) {
Object bean = getBean(FACTORY_BEAN_PREFIX + beanName);
if (bean instanceof FactoryBean) {
FactoryBean<?> factory = (FactoryBean<?>) bean;
boolean isEagerInit;
if (System.getSecurityManager() != null && factory instanceof SmartFactoryBean) {
isEagerInit = AccessController.doPrivileged(
(PrivilegedAction<Boolean>) ((SmartFactoryBean<?>) factory)::isEagerInit,
getAccessControlContext());
}
else {
isEagerInit = (factory instanceof SmartFactoryBean &&
((SmartFactoryBean<?>) factory).isEagerInit());
}
if (isEagerInit) {
getBean(beanName);
}
}
}
else {
getBean(beanName);
}
}
}
// Trigger post-initialization callback for all applicable beans...
for (String beanName : beanNames) {
Object singletonInstance = getSingleton(beanName);
if (singletonInstance instanceof SmartInitializingSingleton) {
SmartInitializingSingleton smartSingleton = (SmartInitializingSingleton) singletonInstance;
if (System.getSecurityManager() != null) {
AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
smartSingleton.afterSingletonsInstantiated();
return null;
}, getAccessControlContext());
}
else {
smartSingleton.afterSingletonsInstantiated();
}
}
}
}
@Override
public Object getBean(String name) throws BeansException {
return doGetBean(name, null, null, false);
}
protected <T> T doGetBean(
String name,
@Nullable Class<T> requiredType,
@Nullable Object[] args,
boolean typeCheckOnly)throws BeansException {
String beanName = transformedBeanName(name);
Object bean;
// Eagerly check singleton cache for manually registered singletons.
Object sharedInstance = getSingleton(beanName);
if (sharedInstance != null && args == null) {
if (logger.isTraceEnabled()) {
if (isSingletonCurrentlyInCreation(beanName)) {
logger.trace("Returning eagerly cached instance of singleton bean '"
+ beanName +
"' that is not fully initialized yet - a consequence of a circular reference");
}
else {
logger.trace("Returning cached instance of singleton bean '" + beanName + "'");
}
}
bean = getObjectForBeanInstance(sharedInstance, name, beanName, null);
}
else {
// Fail if we're already creating this bean instance:
// We're assumably within a circular reference.
if (isPrototypeCurrentlyInCreation(beanName)) {
throw new BeanCurrentlyInCreationException(beanName);
}
// Check if bean definition exists in this factory.
BeanFactory parentBeanFactory = getParentBeanFactory();
if (parentBeanFactory != null && !containsBeanDefinition(beanName)) {
// Not found -> check parent.
String nameToLookup = originalBeanName(name);
if (parentBeanFactory instanceof AbstractBeanFactory) {
return ((AbstractBeanFactory) parentBeanFactory).doGetBean(nameToLookup, requiredType, args, typeCheckOnly);
}
else if (args != null) {
// Delegation to parent with explicit args.
return (T) parentBeanFactory.getBean(nameToLookup, args);
}
else if (requiredType != null) {
// No args -> delegate to standard getBean method.
return parentBeanFactory.getBean(nameToLookup, requiredType);
}
else {
return (T) parentBeanFactory.getBean(nameToLookup);
}
}
if (!typeCheckOnly) {
markBeanAsCreated(beanName);
}
try {
RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
checkMergedBeanDefinition(mbd, beanName, args);
// Guarantee initialization of beans that the current bean depends on.
String[] dependsOn = mbd.getDependsOn();
if (dependsOn != null) {
for (String dep : dependsOn) {
if (isDependent(beanName, dep)) {
throw new BeanCreationException(mbd.getResourceDescription(),
beanName,
"Circular depends-on relationship between '" + beanName + "' and '" + dep + "'");
}
registerDependentBean(dep, beanName);
try {
getBean(dep);
}
catch (NoSuchBeanDefinitionException ex) {
throw new BeanCreationException(mbd.getResourceDescription(),
beanName,
"'" + beanName + "' depends on missing bean '" + dep + "'",
ex);
}
}
}
// Create bean instance.
if (mbd.isSingleton()) {
sharedInstance = getSingleton(beanName, () -> {
try {
return createBean(beanName, mbd, args);
}
catch (BeansException ex) {
// Explicitly remove instance from singleton cache: It might have been put there
// eagerly by the creation process, to allow for circular reference resolution.
// Also remove any beans that received a temporary reference to the bean.
destroySingleton(beanName);
throw ex;
}
});
bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);
}
else if (mbd.isPrototype()) {
// It's a prototype -> create a new instance.
Object prototypeInstance = null;
try {
beforePrototypeCreation(beanName);
prototypeInstance = createBean(beanName, mbd, args);
}
finally {
afterPrototypeCreation(beanName);
}
bean = getObjectForBeanInstance(prototypeInstance, name, beanName, mbd);
}
else {
String scopeName = mbd.getScope();
if (!StringUtils.hasLength(scopeName)) {
throw new IllegalStateException("No scope name defined for bean '" + beanName + "'");
}
Scope scope = this.scopes.get(scopeName);
if (scope == null) {
throw new IllegalStateException("No Scope registered for scope name '" + scopeName + "'");
}
try {
Object scopedInstance = scope.get(beanName, () -> {
beforePrototypeCreation(beanName);
try {
return createBean(beanName, mbd, args);
}
finally {
afterPrototypeCreation(beanName);
}
});
bean = getObjectForBeanInstance(scopedInstance, name, beanName, mbd);
}
catch (IllegalStateException ex) {
throw new BeanCreationException(beanName,
"Scope '" + scopeName + "' is not active for the current thread; consider " +
"defining a scoped proxy for this bean if you intend to refer to it from a singleton",
ex);
}
}
}
catch (BeansException ex) {
cleanupAfterBeanCreationFailure(beanName);
throw ex;
}
}
// Check if required type matches the type of the actual bean instance.
if (requiredType != null && !requiredType.isInstance(bean)) {
try {
T convertedBean = getTypeConverter().convertIfNecessary(bean, requiredType);
if (convertedBean == null) {
throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass());
}
return convertedBean;
}
catch (TypeMismatchException ex) {
if (logger.isTraceEnabled()) {
logger.trace("Failed to convert bean '" + name + "' to required type '" +
ClassUtils.getQualifiedName(requiredType) + "'", ex);
}
throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass());
}
}
return (T) bean;
}
@Override
protected Object createBean(String beanName, RootBeanDefinition mbd, @Nullable Object[] args) throws BeanCreationException {
if (logger.isTraceEnabled()) {
logger.trace("Creating instance of bean '" + beanName + "'");
}
RootBeanDefinition mbdToUse = mbd;
// Make sure bean class is actually resolved at this point, and
// clone the bean definition in case of a dynamically resolved Class
// which cannot be stored in the shared merged bean definition.
Class<?> resolvedClass = resolveBeanClass(mbd, beanName);
if (resolvedClass != null && !mbd.hasBeanClass() && mbd.getBeanClassName() != null) {
mbdToUse = new RootBeanDefinition(mbd);
mbdToUse.setBeanClass(resolvedClass);
}
// Prepare method overrides.
try {
mbdToUse.prepareMethodOverrides();
} catch (BeanDefinitionValidationException ex) {
throw new BeanDefinitionStoreException(
mbdToUse.getResourceDescription(),
beanName,
"Validation of method overrides failed",
ex
);
}
try {
// Give BeanPostProcessors a chance to return a proxy instead of the target bean instance.
Object bean = resolveBeforeInstantiation(beanName, mbdToUse);
if (bean != null) {
return bean;
}
} catch (Throwable ex) {
throw new BeanCreationException(mbdToUse.getResourceDescription(),
beanName,
"BeanPostProcessor before instantiation of bean failed",
ex);
}
try {
Object beanInstance = doCreateBean(beanName, mbdToUse, args);
if (logger.isTraceEnabled()) {
logger.trace("Finished creating instance of bean '" + beanName + "'");
}
return beanInstance;
} catch (BeanCreationException | ImplicitlyAppearedSingletonException ex) {
// A previously detected exception with proper bean creation context already,
// or illegal singleton state to be communicated up to DefaultSingletonBeanRegistry.
throw ex;
} catch (Throwable ex) {
throw new BeanCreationException(mbdToUse.getResourceDescription(), beanName, "Unexpected exception during bean creation", ex);
}
}
protected Object doCreateBean(String beanName, RootBeanDefinition mbd, @Nullable Object[] args) throws BeanCreationException {
// Instantiate the bean.
BeanWrapper instanceWrapper = null;
if (mbd.isSingleton()) {
instanceWrapper = this.factoryBeanInstanceCache.remove(beanName);
}
if (instanceWrapper == null) {
instanceWrapper = createBeanInstance(beanName, mbd, args);
}
//在这里对象被实例化但是只是类对象并不是Bean
Object bean = instanceWrapper.getWrappedInstance();
Class<?> beanType = instanceWrapper.getWrappedClass();
if (beanType != NullBean.class) {
mbd.resolvedTargetType = beanType;
}
// Allow post-processors to modify the merged bean definition.
synchronized (mbd.postProcessingLock) {
if (!mbd.postProcessed) {
try {
applyMergedBeanDefinitionPostProcessors(mbd, beanType, beanName);
} catch (Throwable ex) {
throw new BeanCreationException(mbd.getResourceDescription(), beanName,
"Post-processing of merged bean definition failed", ex);
}
mbd.postProcessed = true;
}
}
// Eagerly cache singletons to be able to resolve circular references
// even when triggered by lifecycle interfaces like BeanFactoryAware.
boolean earlySingletonExposure = (mbd.isSingleton() && this.allowCircularReferences && isSingletonCurrentlyInCreation(beanName));
if (earlySingletonExposure) {
if (logger.isTraceEnabled()) {
logger.trace("Eagerly caching bean '" + beanName +
"' to allow for resolving potential circular references");
}
addSingletonFactory(beanName, () -> getEarlyBeanReference(beanName, mbd, bean));
}
// Initialize the bean instance.
Object exposedObject = bean;
try {
populateBean(beanName, mbd, instanceWrapper);
exposedObject = initializeBean(beanName, exposedObject, mbd);
} catch (Throwable ex) {
if (ex instanceof BeanCreationException && beanName.equals(((BeanCreationException) ex).getBeanName())) {
throw (BeanCreationException) ex;
} else {
throw new BeanCreationException(mbd.getResourceDescription(), beanName, "Initialization of bean failed", ex);
}
}
if (earlySingletonExposure) {
Object earlySingletonReference = getSingleton(beanName, false);
if (earlySingletonReference != null) {
if (exposedObject == bean) {
exposedObject = earlySingletonReference;
} else if (!this.allowRawInjectionDespiteWrapping && hasDependentBean(beanName)) {
String[] dependentBeans = getDependentBeans(beanName);
Set<String> actualDependentBeans = new LinkedHashSet<>(dependentBeans.length);
for (String dependentBean : dependentBeans) {
if (!removeSingletonIfCreatedForTypeCheckOnly(dependentBean)) {
actualDependentBeans.add(dependentBean);
}
}
if (!actualDependentBeans.isEmpty()) {
throw new BeanCurrentlyInCreationException(beanName,
"Bean with name '" + beanName + "' has been injected into other beans [" +
StringUtils.collectionToCommaDelimitedString(actualDependentBeans) +
"] in its raw version as part of a circular reference, but has eventually been " +
"wrapped. This means that said other beans do not use the final version of the " +
"bean. This is often the result of over-eager type matching - consider using " +
"'getBeanNamesForType' with the 'allowEagerInit' flag turned off, for example.");
}
}
}
}
// Register bean as disposable.
try {
registerDisposableBeanIfNecessary(beanName, bean, mbd);
} catch (BeanDefinitionValidationException ex) {
throw new BeanCreationException(
mbd.getResourceDescription(), beanName, "Invalid destruction signature", ex);
}
return exposedObject;
}
protected Object initializeBean(String beanName, Object bean, @Nullable RootBeanDefinition mbd) {
if (System.getSecurityManager() != null) {
AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
invokeAwareMethods(beanName, bean);
return null;
}, getAccessControlContext());
} else {
invokeAwareMethods(beanName, bean);
}
Object wrappedBean = bean;
if (mbd == null || !mbd.isSynthetic()) {
wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);
}
try {
invokeInitMethods(beanName, wrappedBean, mbd);
} catch (Throwable ex) {
throw new BeanCreationException(
(mbd != null ? mbd.getResourceDescription() : null),
beanName, "Invocation of init method failed", ex);
}
if (mbd == null || !mbd.isSynthetic()) {
wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);
}
return wrappedBean;
}
下面来到重头戏，我们进入到invokeAwareMethods(String beanName, Object bean)方法，咱们可以很明显的看到该方法其实就是在判断，当前的类对象是否实现了Aware接口，并且一个一个判断。而且这里的Aware接口的注入Spring使用了set()方法注入。
private void invokeAwareMethods(String beanName, Object bean) {
if (bean instanceof Aware) {
if (bean instanceof BeanNameAware) {
((BeanNameAware) bean).setBeanName(beanName);
}
if (bean instanceof BeanClassLoaderAware) {
ClassLoader bcl = getBeanClassLoader();
if (bcl != null) {
((BeanClassLoaderAware) bean).setBeanClassLoader(bcl);
}
}
if (bean instanceof BeanFactoryAware) {
((BeanFactoryAware) bean).setBeanFactory(AbstractAutowireCapableBeanFactory.this);
}
}
}
@Override
public Object applyBeanPostProcessorsBeforeInitialization(Object existingBean, String beanName)
throws BeansException {
Object result = existingBean;
for (BeanPostProcessor processor : getBeanPostProcessors()) {
Object current = processor.postProcessBeforeInitialization(result, beanName);
if (current == null) {
return result;
}
result = current;
}
return result;
}
可以看到第7行的processor.postProcessBeforeInitialization(result, beanName);方法，我要的是postProcessBeforeInitialization()方法的实现。
当前要进入的是ApplicationContextAwareProcessor。
我们可以到在ApplicationContextAwareProcessor中的postProcessBeforeInitialization()中，将当前的对象一个一个的判断他到底是实现了那个Aware接口。
public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
if (!(bean instanceof EnvironmentAware || bean instanceof EmbeddedValueResolverAware ||
bean instanceof ResourceLoaderAware || bean instanceof ApplicationEventPublisherAware ||
bean instanceof MessageSourceAware || bean instanceof ApplicationContextAware)){
//如果发现当前对象实现的Aware接口不是Spring提供的就会直接返回
return bean;
}
AccessControlContext acc = null;
if (System.getSecurityManager() != null) {
acc = this.applicationContext.getBeanFactory().getAccessControlContext();
}
if (acc != null) {
AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
invokeAwareInterfaces(bean);
return null;
}, acc);
}
else {
invokeAwareInterfaces(bean);
}
return bean;
}
实例化当前对象实现的Aware接口。
private void invokeAwareInterfaces(Object bean) {
if (bean instanceof EnvironmentAware) {
((EnvironmentAware) bean).setEnvironment(this.applicationContext.getEnvironment());
}
if (bean instanceof EmbeddedValueResolverAware) {
((EmbeddedValueResolverAware) bean).setEmbeddedValueResolver(this.embeddedValueResolver);
}
if (bean instanceof ResourceLoaderAware) {
((ResourceLoaderAware) bean).setResourceLoader(this.applicationContext);
}
if (bean instanceof ApplicationEventPublisherAware) {
((ApplicationEventPublisherAware) bean).setApplicationEventPublisher(this.applicationContext);
}
if (bean instanceof MessageSourceAware) {
((MessageSourceAware) bean).setMessageSource(this.applicationContext);
}
if (bean instanceof ApplicationContextAware) {
((ApplicationContextAware) bean).setApplicationContext(this.applicationContext);
}
}
最后在上述代码的第18行的时候就会将当前的applicationContext设置给se()方法中。
- 下面具体的Debug就不在本文中详细的做笔记了，因为上述的流程其实已经说的十分详细了，所以在这里就不说了，下面要讲的是，ignoreDependencyInterface(Class<?> ifc);方法到底是干啥的？对于spring整体来说他有什么用？
- 是这样的之前我们写过一个类该实现了ApplicationContextAware接口，在该类中我们定义了一个ApplicationContext，意图是想要注入ApplicationContext到当前的类中，并进行使用。
@Slf4j(topic = "spring-student:")
@Component
public class Z implements ApplicationContextAware {
ApplicationContext applicationContext;
@Override
public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
this.applicationContext = applicationContext;
System.out.println("applicationContext-name:{}" + applicationContext.getClass().getSimpleName());
System.out.println("当前spring容器中已经有了,你在可以在你的Z中随意使用~~~");
}
}
- 那么在这里其实有一点需要注意的是，ApplicationContext这个Bean在springContext中其实是比较特殊的，并不像是其他较为普通的Bean，他在spring中是作为Spring-context其实也就是spring的ioc容器。
- 所以在这里有个很大的问题，你在这里类中想要依赖注入applicationContext，但假如我当前的applicationContext没有被准备好，你就拿来用是不是不行！！！
- 所以说Spring在这里对于上述的场景给开发人员提供一个Aware接口来方便程序员可以不破坏当前对于applicationContext的规则并且可以做到获取到applicationContext。
- 其实这里的实现是在refresh()方法中的prepareBeanFactory(beanFactory);见名知意，做一些beanFactory的准备工作。
- 其实本章节我们重点讨论的是在Aware接口的含义，或者说他的存在的意义：
- 获取Spring容器提供的一些特定对象，或者让你的bean具备一些特殊的能力。
- 保证你获取的这些特性对象是正确的，而不是通过依赖注入得到的(因为有些特殊的bean，直接通过依赖注入会有问题)。
