Spring的@Scope注解詳細(xì)解析
@Scope是什么,有什么用?
@Scope注解主要作用是調(diào)節(jié)Ioc容器中的作用域,在Spring IoC容器中主要有以下五種作用域:
基本作用域:singleton(單例)、prototype(多例);Web 作用域(reqeust、session、globalsession),自定義作用域。
@Scope注解源碼解析
使用@Scope注解對象注入到IOC容器過程
(1) springboot 程序啟動時會對classpath路徑下的包中的類進(jìn)行掃描,將類解析成BeanDefinition,在掃描完BeanDefinition后會對其進(jìn)行注冊,便于后面創(chuàng)建Bean時使用
// org.springframework.context.annotation.ClassPathBeanDefinitionScanner#doScan
/**
* Perform a scan within the specified base packages,
* returning the registered bean definitions.
* <p>This method does <i>not</i> register an annotation config processor
* but rather leaves this up to the caller.
* @param basePackages the packages to check for annotated classes
* @return set of beans registered if any for tooling registration purposes (never {@code null})
*/
protected Set<BeanDefinitionHolder> doScan(String... basePackages) {
Assert.notEmpty(basePackages, "At least one base package must be specified");
Set<BeanDefinitionHolder> beanDefinitions = new LinkedHashSet<>();
for (String basePackage : basePackages) {
Set<BeanDefinition> candidates = findCandidateComponents(basePackage);
for (BeanDefinition candidate : candidates) {
ScopeMetadata scopeMetadata = this.scopeMetadataResolver.resolveScopeMetadata(candidate);
candidate.setScope(scopeMetadata.getScopeName());
String beanName = this.beanNameGenerator.generateBeanName(candidate, this.registry);
if (candidate instanceof AbstractBeanDefinition) {
postProcessBeanDefinition((AbstractBeanDefinition) candidate, beanName);
}
if (candidate instanceof AnnotatedBeanDefinition) {
AnnotationConfigUtils.processCommonDefinitionAnnotations((AnnotatedBeanDefinition) candidate);
}
if (checkCandidate(beanName, candidate)) {
BeanDefinitionHolder definitionHolder = new BeanDefinitionHolder(candidate, beanName);
definitionHolder =
AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry);
beanDefinitions.add(definitionHolder);
registerBeanDefinition(definitionHolder, this.registry);
}
}
}
return beanDefinitions;
}(2)接著會對掃描出來的BeanDefinition處理,其中下面代碼對掃描完的Bean的作用域的代理模式進(jìn)行處理:
// org.springframework.context.annotation.AnnotationConfigUtils#applyScopedProxyMode
static BeanDefinitionHolder applyScopedProxyMode(
ScopeMetadata metadata, BeanDefinitionHolder definition, BeanDefinitionRegistry registry) {
ScopedProxyMode scopedProxyMode = metadata.getScopedProxyMode();
if (scopedProxyMode.equals(ScopedProxyMode.NO)) {
return definition;
}
boolean proxyTargetClass = scopedProxyMode.equals(ScopedProxyMode.TARGET_CLASS);
return ScopedProxyCreator.createScopedProxy(definition, registry, proxyTargetClass);
}上面代碼會判斷作用域的代碼模式,如果是ScopedProxyMode.NO,不進(jìn)行代理處理直接返回BeanDefinition,如果不是NO,再判斷是否是ScopedProxyMode.TARGET_CLASS,在后續(xù)邏輯中會根據(jù)此來決定是否創(chuàng)建目標(biāo)類的代理類。
// org.springframework.aop.scope.ScopedProxyUtils#createScopedProxy
public static BeanDefinitionHolder createScopedProxy(BeanDefinitionHolder definition,
BeanDefinitionRegistry registry, boolean proxyTargetClass) {
String originalBeanName = definition.getBeanName();
BeanDefinition targetDefinition = definition.getBeanDefinition();
String targetBeanName = getTargetBeanName(originalBeanName);
// Create a scoped proxy definition for the original bean name,
// "hiding" the target bean in an internal target definition.
RootBeanDefinition proxyDefinition = new RootBeanDefinition(ScopedProxyFactoryBean.class);
proxyDefinition.setDecoratedDefinition(new BeanDefinitionHolder(targetDefinition, targetBeanName));
proxyDefinition.setOriginatingBeanDefinition(targetDefinition);
proxyDefinition.setSource(definition.getSource());
proxyDefinition.setRole(targetDefinition.getRole());
proxyDefinition.getPropertyValues().add("targetBeanName", targetBeanName);
if (proxyTargetClass) {
targetDefinition.setAttribute(AutoProxyUtils.PRESERVE_TARGET_CLASS_ATTRIBUTE, Boolean.TRUE);
// ScopedProxyFactoryBean's "proxyTargetClass" default is TRUE, so we don't need to set it explicitly here.
}
else {
proxyDefinition.getPropertyValues().add("proxyTargetClass", Boolean.FALSE);
}
// Copy autowire settings from original bean definition.
proxyDefinition.setAutowireCandidate(targetDefinition.isAutowireCandidate());
proxyDefinition.setPrimary(targetDefinition.isPrimary());
if (targetDefinition instanceof AbstractBeanDefinition) {
proxyDefinition.copyQualifiersFrom((AbstractBeanDefinition) targetDefinition);
}
// The target bean should be ignored in favor of the scoped proxy.
targetDefinition.setAutowireCandidate(false);
targetDefinition.setPrimary(false);
// Register the target bean as separate bean in the factory.
registry.registerBeanDefinition(targetBeanName, targetDefinition);
// Return the scoped proxy definition as primary bean definition
// (potentially an inner bean).
return new BeanDefinitionHolder(proxyDefinition, originalBeanName, definition.getAliases());
}上面過程向BeanDefinitionRegistry中注入了兩個BeanDefinition分別是目標(biāo)類、目標(biāo)類的代理類(beanClass為ScopedProxyFactoryBean.class)。
最終返回BeanDefinitionHolder的beanName為目標(biāo)類名,beanClass為ScopedProxyFactoryBean.class的BeanDenifition。
return new BeanDefinitionHolder(proxyDefinition, originalBeanName, definition.getAliases());
其中ScopedProxyFactoryBean類實現(xiàn)了BeanFactoryAware,Aware接口由Spring在AbstractAutowireCapableBeanFactory.initializeBean(beanName, bean,mbd)方法中通過調(diào)用invokeAwareMethods(beanName, bean)方法和applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName)觸發(fā)Aware方法的調(diào)用setBeanFactory方法,該方法中會創(chuàng)建一個目前類的代理類暫存在其proxy變量中。
// org.springframework.aop.scope.ScopedProxyFactoryBean#setBeanFactory
@Override
public void setBeanFactory(BeanFactory beanFactory) {
if (!(beanFactory instanceof ConfigurableBeanFactory)) {
throw new IllegalStateException("Not running in a ConfigurableBeanFactory: " + beanFactory);
}
ConfigurableBeanFactory cbf = (ConfigurableBeanFactory) beanFactory;
this.scopedTargetSource.setBeanFactory(beanFactory);
ProxyFactory pf = new ProxyFactory();
pf.copyFrom(this);
pf.setTargetSource(this.scopedTargetSource);
Assert.notNull(this.targetBeanName, "Property 'targetBeanName' is required");
Class<?> beanType = beanFactory.getType(this.targetBeanName);
if (beanType == null) {
throw new IllegalStateException("Cannot create scoped proxy for bean '" + this.targetBeanName +
"': Target type could not be determined at the time of proxy creation.");
}
if (!isProxyTargetClass() || beanType.isInterface() || Modifier.isPrivate(beanType.getModifiers())) {
pf.setInterfaces(ClassUtils.getAllInterfacesForClass(beanType, cbf.getBeanClassLoader()));
}
// Add an introduction that implements only the methods on ScopedObject.
ScopedObject scopedObject = new DefaultScopedObject(cbf, this.scopedTargetSource.getTargetBeanName());
pf.addAdvice(new DelegatingIntroductionInterceptor(scopedObject));
// Add the AopInfrastructureBean marker to indicate that the scoped proxy
// itself is not subject to auto-proxying! Only its target bean is.
pf.addInterface(AopInfrastructureBean.class);
this.proxy = pf.getProxy(cbf.getBeanClassLoader());
}在注入目標(biāo)對象時,將會時用beanName從BeanDefinitionRegistry中取出beanclass為ScopedProxyFactoryBean.class的BeanDenifition,使用該BeanDenifition創(chuàng)建一個實例,創(chuàng)建完實例后會調(diào)用getObjectForBeanInstance方法來獲取beanInstance,如果時FactoryBean則會調(diào)用其getObject()方法。
// org.springframework.beans.factory.support.AbstractBeanFactory#doGetBean
// 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;
}
});
beanInstance = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);
}// org.springframework.beans.factory.support.AbstractBeanFactory#getObjectForBeanInstance
protected Object getObjectForBeanInstance(
Object beanInstance, String name, String beanName, @Nullable RootBeanDefinition mbd) {
// Don't let calling code try to dereference the factory if the bean isn't a factory.
if (BeanFactoryUtils.isFactoryDereference(name)) {
if (beanInstance instanceof NullBean) {
return beanInstance;
}
if (!(beanInstance instanceof FactoryBean)) {
throw new BeanIsNotAFactoryException(beanName, beanInstance.getClass());
}
if (mbd != null) {
mbd.isFactoryBean = true;
}
return beanInstance;
}
// Now we have the bean instance, which may be a normal bean or a FactoryBean.
// If it's a FactoryBean, we use it to create a bean instance, unless the
// caller actually wants a reference to the factory.
if (!(beanInstance instanceof FactoryBean)) {
return beanInstance;
}
Object object = null;
if (mbd != null) {
mbd.isFactoryBean = true;
}
else {
object = getCachedObjectForFactoryBean(beanName);
}
if (object == null) {
// Return bean instance from factory.
FactoryBean<?> factory = (FactoryBean<?>) beanInstance;
// Caches object obtained from FactoryBean if it is a singleton.
if (mbd == null && containsBeanDefinition(beanName)) {
mbd = getMergedLocalBeanDefinition(beanName);
}
boolean synthetic = (mbd != null && mbd.isSynthetic());
object = getObjectFromFactoryBean(factory, beanName, !synthetic);
}
return object;
}目標(biāo)類會被解析成ScopedProxyFactoryBean,而ScopedProxyFactoryBean是FactoryBean,所以會調(diào)用ScopedProxyFactoryBean的getObject方法,而ScopedProxyFactoryBean的getObject方法返回的是其屬性proxy即創(chuàng)建的目標(biāo)類的代理類,
@Override
public Object getObject() {
if (this.proxy == null) {
throw new FactoryBeanNotInitializedException();
}
return this.proxy;
}到此這篇關(guān)于Spring的@Scope注解詳細(xì)解析的文章就介紹到這了,更多相關(guān)@Scope注解內(nèi)容請搜索腳本之家以前的文章或繼續(xù)瀏覽下面的相關(guān)文章希望大家以后多多支持腳本之家!
相關(guān)文章
Spring @async方法如何添加注解實現(xiàn)異步調(diào)用
這篇文章主要介紹了Spring @async方法如何添加注解實現(xiàn)異步調(diào)用,文中通過示例代碼介紹的非常詳細(xì),對大家的學(xué)習(xí)或者工作具有一定的參考學(xué)習(xí)價值,需要的朋友可以參考下2020-01-01
java通過模擬post方式提交表單實現(xiàn)圖片上傳功能實例
這篇文章主要介紹了java通過模擬post方式提交表單實現(xiàn)圖片上傳功能實例,涉及Java針對表單的提交操作響應(yīng)及文件傳輸?shù)南嚓P(guān)技巧,具有一定參考借鑒價值,需要的朋友可以參考下2015-11-11
Java并發(fā)編程必備之Synchronized關(guān)鍵字深入解析
本文我們深入探索了Java中的Synchronized關(guān)鍵字,包括其互斥性和可重入性的特性,文章詳細(xì)介紹了Synchronized的三種使用方式:修飾代碼塊、修飾普通方法和修飾靜態(tài)方法,感興趣的朋友一起看看吧2025-04-04
Java多線程之 FutureTask:帶有返回值的函數(shù)定義和調(diào)用方式
這篇文章主要介紹了Java多線程之 FutureTask:帶有返回值的函數(shù)定義和調(diào)用方式,具有很好的參考價值,希望對大家有所幫助。如有錯誤或未考慮完全的地方,望不吝賜教2021-07-07
Spring Boot結(jié)合IDEA自帶Maven插件如何快速切換profile
IDEA是目前 Java 開發(fā)者中使用最多的開發(fā)工具,它有著簡約的設(shè)計風(fēng)格,強(qiáng)大的集成工具,便利的快捷鍵,這篇文章主要介紹了Spring Boot結(jié)合IDEA自帶Maven插件快速切換profile,需要的朋友可以參考下2023-03-03

