Spring循环依赖那些事儿（含Spring详细流程图）

Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'taskPunchEvent': Injection of resource dependencies failed; nested exception is org.springframework.beans.factory.BeanCurrentlyInCreationException: Error creating bean with name 'playContentService': Bean with name 'playContentService' has been injected into other beans [toVoConvertor] 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.  at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor.postProcessProperties(CommonAnnotationBeanPostProcessor.java:325)  at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1404)  at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:592)  at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:515)  at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:320)  at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222)  at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:318)  at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:199)  at org.springframework.beans.factory.config.DependencyDescriptor.resolveCandidate(DependencyDescriptor.java:277)  at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1255)  at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1175)  at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:595)  ... 40 moreCaused by: org.springframework.beans.factory.BeanCurrentlyInCreationException: Error creating bean with name 'playContentService': Bean with name 'playContentService' has been injected into other beans [toVoConvertor] 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.  at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:622)  at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:515)  at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:320)  at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222)  at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:318)  at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:204)  at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.resolveBeanByName(AbstractAutowireCapableBeanFactory.java:452)  at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor.autowireResource(CommonAnnotationBeanPostProcessor.java:527)  at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor.getResource(CommonAnnotationBeanPostProcessor.java:497)  at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor$ResourceElement.getResourceToInject(CommonAnnotationBeanPostProcessor.java:637)  at org.springframework.beans.factory.annotation.InjectionMetadata$InjectedElement.inject(InjectionMetadata.java:180)  at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:90)  at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor.postProcessProperties(CommonAnnotationBeanPostProcessor.java:322)  ... 51 more

Spring创建Bean - #DefaultListableBeanFactory#preInstantiateSingletons
@Overridepublic void preInstantiateSingletons() throws BeansException {        //......        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)) {                //FactoryBean接口处理                ......            }            else {                //正常Bean的加载入口                getBean(beanName);            }        }    }        //......}

//构造器循环依赖示例
public class StudentA {     private StudentB studentB ; 
    public StudentA(StudentB studentB) {        this.studentB = studentB;    }}
public class StudentB {     private StudentA studentA ;        public StudentB(StudentA studentA) {        this.studentA = studentA;    }}

@Overridepublic PropertyValues postProcessProperties(PropertyValues pvs, Object bean, String beanName) {    InjectionMetadata metadata = findAutowiringMetadata(beanName, bean.getClass(), pvs);    try {        //属性注入        metadata.inject(bean, beanName, pvs);    }    catch (BeanCreationException ex) {        throw ex;    }    catch (Throwable ex) {        throw new BeanCreationException(beanName, "Injection of autowired dependencies failed", ex);    }    return pvs;}

protected Object doCreateBean(final String beanName, final RootBeanDefinition mbd, final Object[] args) {        BeanWrapper instanceWrapper = null;
    if (instanceWrapper == null) {        //创建Bean        instanceWrapper = createBeanInstance(beanName, mbd, args);    }            .....        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));    }
    //填充Bean依赖与Bean的初始化    Object exposedObject = bean;    try {        //填充依赖的bean实例        populateBean(beanName, mbd, instanceWrapper);        //初始化---注意！注意！注意！此方法中可能调用 BeanPostProcessor        //的applyBeanPostProcessorsAfterInitialization时可能会返回代理对象，如果代理途径与创建时代理方式不同则也会产生不同代理对象        //从而产生循环依赖中对象不一致情况        exposedObject = initializeBean(beanName, exposedObject, mbd);    }
    //如果存在循环依赖，则保证最开始创建的Bean需要是循环依赖 getEarlyBeanReference触发生成的bean    //因为getEarlyBeanReference 可能返回的是代理类，因为singleton必须全局唯一    if (earlySingletonExposure) {        Object earlySingletonReference = getSingleton(beanName, false);        //只有真正存在循环依赖时，才会触发 getEarlyBeanReference调用产生EarlyBean        //未存在循环依赖，则getEarlyBeanReference不触发，earlySingletonReference为null，返回exposedObject即可        if (earlySingletonReference != null) {            if (exposedObject == bean) {                exposedObject = earlySingletonReference;            }            else if (!this.allowRawInjectionDespiteWrapping && hasDependentBean(beanName)) {                ......                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.");                }            }        }    }    return exposedObject;}

protected Object getSingleton(String beanName, boolean allowEarlyReference) {    //一级缓存(单例池)获取Bean    Object singletonObject = this.singletonObjects.get(beanName);    if (singletonObject == null && isSingletonCurrentlyInCreation(beanName)) {        synchronized (this.singletonObjects) {            //二级缓存获取(提前暴露不完全)Bean            singletonObject = this.earlySingletonObjects.get(beanName);            if (singletonObject == null && allowEarlyReference) {                ObjectFactory<?> singletonFactory = this.singletonFactories.get(beanName);                if (singletonFactory != null) {                    //三级缓存Bean的创建工厂获取bean(可提前被代理)                    singletonObject = singletonFactory.getObject();                    this.earlySingletonObjects.put(beanName, singletonObject);                    this.singletonFactories.remove(beanName);                }            }        }    }    return singletonObject;}

//提供提前创建并返回代理的工厂singletonFactory.getObject()执行的是个回调//addSingletonFactory(beanName, () -> getEarlyBeanReference(beanName, mbd, bean));
protected Object getEarlyBeanReference(String beanName, RootBeanDefinition mbd, Object bean) {    Object exposedObject = bean;    if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) {        for (BeanPostProcessor bp : getBeanPostProcessors()) {            //getEarlyBeanReference是SmartInstantiationAwareBeanPostProcessor接口定义方法，            //此方法很关键(构造函数推断也在此定义)            if (bp instanceof SmartInstantiationAwareBeanPostProcessor) {                SmartInstantiationAwareBeanPostProcessor ibp = (SmartInstantiationAwareBeanPostProcessor) bp;                exposedObject = ibp.getEarlyBeanReference(exposedObject, beanName);            }        }    }    return exposedObject;}

public Object resolveDependency(DependencyDescriptor descriptor, @Nullable String requestingBeanName,                                @Nullable Set<String> autowiredBeanNames, @Nullable TypeConverter typeConverter) throws BeansException {
    descriptor.initParameterNameDiscovery(getParameterNameDiscoverer());    if (Optional.class == descriptor.getDependencyType()) {        return createOptionalDependency(descriptor, requestingBeanName);    }    ......    else {        //处理@lazy        Object result = getAutowireCandidateResolver().getLazyResolutionProxyIfNecessary(            descriptor, requestingBeanName);        if (result == null) {            result = doResolveDependency(descriptor, requestingBeanName, autowiredBeanNames, typeConverter);        }        return result;    }}
ContextAnnotationAutowireCandidateResolver#getLazyResolutionProxyIfNecessarypublic Object getLazyResolutionProxyIfNecessary(DependencyDescriptor descriptor, @Nullable String beanName) {    return (isLazy(descriptor) ? buildLazyResolutionProxy(descriptor, beanName) : null);}
ContextAnnotationAutowireCandidateResolver#isLazy//是否为@lazy，如果为@lazy则创建依赖代理protected boolean isLazy(DependencyDescriptor descriptor) {    for (Annotation ann : descriptor.getAnnotations()) {        Lazy lazy = AnnotationUtils.getAnnotation(ann, Lazy.class);        if (lazy != null && lazy.value()) {            return true;        }    }    .......}

import org.junit.Test;import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;import org.springframework.context.annotation.AnnotationConfigApplicationContext;import org.springframework.context.annotation.Bean;import org.springframework.context.annotation.ComponentScan;import org.springframework.context.annotation.Configuration;import org.springframework.context.annotation.EnableAspectJAutoProxy;import org.springframework.core.env.Environment;import org.springframework.dao.annotation.PersistenceExceptionTranslationPostProcessor;import org.springframework.stereotype.Component;import org.springframework.stereotype.Repository;import javax.annotation.Resource;/** * @author: Superizer */@Componentpublic class MainSpringCircularDependencyTester{    @Test    public void springCircularDependencyTest()    {        AnnotationConfigApplicationContext ac = new AnnotationConfigApplicationContext(SpringCircularDependencyConfig.class);        X x = ac.getBean(X.class);        System.out.println("Spring bean X =" + x.getClass().getName());        x.display();        Y y = ac.getBean(Y.class);        System.out.println("Spring bean Y =" + y.getClass().getName());        y.display();        Z z = ac.getBean(Z.class);        System.out.println("Spring bean Z =" + z.getClass().getName());        z.display();        System.out.println("******************Main********************");    }    @Configuration    @ComponentScan("com.myself.demo.spring.v5.circular.dependency")//  @EnableAspectJAutoProxy    @ConditionalOnClass(PersistenceExceptionTranslationPostProcessor.class)    static class SpringCircularDependencyConfig{        @Bean        @ConditionalOnMissingBean        @ConditionalOnProperty(prefix = "spring.dao.exceptiontranslation", name = "enabled",                matchIfMissing = true)        public static PersistenceExceptionTranslationPostProcessor        persistenceExceptionTranslationPostProcessor(Environment environment) {            PersistenceExceptionTranslationPostProcessor postProcessor = new PersistenceExceptionTranslationPostProcessor();            boolean proxyTargetClass = environment.getProperty(                    "spring.aop.proxy-target-class", Boolean.class, Boolean.TRUE);            postProcessor.setProxyTargetClass(proxyTargetClass);            return postProcessor;        }    }    abstract static class A {        public abstract A injectSources();        public abstract A self();        public void display(){            System.out.println("injectSources:" + injectSources().getClass().getName());            System.out.println("*******************************************************");        }    }    //X、Y、Z 只要循环依赖中第一个类X有注解@Repository，就会出现循环依赖异常    //执行X的singletonFactory.getObject()返回的原对象，但是后边初始化时    //执行到PersistenceExceptionTranslationPostProcessor时单独创建代理逻辑返回的是代理类    //exposedObject = initializeBean(beanName, exposedObject, mbd);    @Repository//  @Component    static class X  extends A{        @Resource        private Y y;        @Override        public Y injectSources()        {            return y;        }        @Override        public X self() {            return this;        }    }    @Component//  @Repository    static class Y extends A{        @Resource        private Z z;        @Override        public Z injectSources() {            return z;        }        @Override        public Y self()        {            return this;        }    }    @Component//  @Repository    static class Z extends A{        @Resource        private X x;        @Override        public X injectSources()        {            return x;        }        @Override        public Z self()        {            return this;        }    }}

import org.aopalliance.intercept.MethodInterceptor;import org.aopalliance.intercept.MethodInvocation;import org.junit.Test;import org.springframework.aop.ClassFilter;import org.springframework.aop.MethodMatcher;import org.springframework.aop.Pointcut;import org.springframework.aop.framework.autoproxy.BeanNameAutoProxyCreator;import org.springframework.aop.support.AbstractExpressionPointcut;import org.springframework.aop.support.DefaultPointcutAdvisor;import org.springframework.context.annotation.AnnotationConfigApplicationContext;import org.springframework.context.annotation.Bean;import org.springframework.context.annotation.ComponentScan;import org.springframework.context.annotation.Configuration;import org.springframework.context.annotation.EnableAspectJAutoProxy;import org.springframework.stereotype.Component;import javax.annotation.Resource;import java.util.Arrays;/** * @author: Superizer * Copyright (C) 2021 * All rights reserved */@Componentpublic class MainSpringCircularDependencyV2Tester{    @Test    public void circularDependencyV2Tester()    {        AnnotationConfigApplicationContext ac = new AnnotationConfigApplicationContext(SpringCircularDependencyConfig.class);        A a = ac.getBean(A.class);        System.out.println("Spring bean A =" + a.getClass().getName());        a.display();        B y = ac.getBean(B.class);        System.out.println("Spring bean B =" + y.getClass().getName());        y.display();        C z = ac.getBean(C.class);        System.out.println("Spring bean C =" + z.getClass().getName());        z.display();        System.out.println("******************Main********************");    }    @Configuration    @ComponentScan("com.myself.demo.spring.v5.circular.dependency.v2")    @EnableAspectJAutoProxy    static class SpringCircularDependencyConfig {        @Bean        public DefaultPointcutAdvisor defaultPointcutAdvisor() {            DefaultPointcutAdvisor advisor = new DefaultPointcutAdvisor();            Pointcut pointcut = new AbstractExpressionPointcut() {                @Override                public ClassFilter getClassFilter() {                    return (tmp) -> {                        String name = tmp.getName();                        if(name.equals(A.class.getName())) {                            return true;                        }                        return false;                    };                }                @Override                public MethodMatcher getMethodMatcher() {                    return MethodMatcher.TRUE;                }            };            advisor.setPointcut(pointcut);            advisor.setAdvice(new SpringAopAroundMethod());            advisor.setOrder(0);            return advisor;        }        @Bean        public BeanNameAutoProxyCreator beanNameAutoProxyCreator() {            BeanNameAutoProxyCreator apc = new BeanNameAutoProxyCreator();            apc.setBeanNames("a");            apc.setOrder(-1);            apc.setProxyTargetClass(true);            return apc;        }    }    abstract static class G {        public abstract G injectSources();        public abstract G self();        public void display(){            System.out.println("injectSources:" + injectSources().getClass().getName());            System.out.println("*******************************************************");        }    }    @Component(value = "a")    static class A  extends G {        @Resource        private B b;        @Override        public B injectSources()        {            return b;        }        @Override        public A self() {            return this;        }    }    @Component    static class B extends G {        @Resource        private C c;        @Override        public C injectSources() {            return c;        }        @Override        public B self()        {            return this;        }    }    @Component    static class C extends G {        @Resource        private A a;        @Override        public A injectSources()        {            return a;        }        @Override        public C self()        {            return this;        }    }    static class SpringAopAroundMethod implements MethodInterceptor {        @Override        public Object invoke(MethodInvocation methodInvocation) throws Throwable {            System.out.println("Aop Before method!");            try {                Object result = methodInvocation.proceed();                System.out.println("Aop after method!");                return result;            } catch (IllegalArgumentException e) {                System.out.println("Aop throw exception!");                throw e;            }        }    }}