Spring三级缓存解决循环引用-时序图

getSingleton(beanName)

将a从三级缓存删除放入二级缓存

return a的对象

instantiationStrategy : SimpleInstantiationStrategy

开始逐个处理配置类

beanFactory : DefaultListableBeanFactory

return T

return b

BeanUtils

return NULL

return instanceWrapper

BeanUtils.instantiateClass(constructorToUse)

this.beanFactory.getBean(resolvedName)

将a对象从二级缓存删除放入到一级缓存

valueResolver : BeanDefinitionValueResolver

开始处理b的依赖属性a

populateBean执行完毕

自定义Bean的构造

getBean(beanName)

doCreateBean执行完毕，返回b对象

将b放入一级缓存

getObject()执行完毕

接下来重复循环加载下一个类，也就是b，会直接从一级缓存中读取

AbstractBeanFactory

getObject执行完毕

singletonFactory.getObject()

doGetBean(name)执行完毕

return null

将a放入三级缓存

package com.spring.debug.l3.cache.bean;public class B { private String nameB; private int ageB; private A a; public B(){ System.out.println(\"======初始化B......\"); } public String getNameB() { return nameB; } public void setNameB(String nameB) { this.nameB = nameB; } public int getAgeB() { return ageB; } public void setAgeB(int ageB) { this.ageB = ageB; } public A getA() { return a; } public void setA(A a) { this.a = a; }}

构造b对象

DefaultSingletonBeanRegistry

doCreateBean执行完毕

createBean执行完毕

开始处理a的依赖属性b

getBean(beanName)执行完毕

ClassPathXmlApplicationContext

构造a对象

AbstractApplicationContext

构造A对象

refresh()

return b对象

finishBeanFactoryInitialization(beanFactory)

DEBUG数据说明

return b对象，sharedInstance接收

package com.spring.debug.l3.cache.bean;public class A { private String nameA; private int ageA; private B b; public A(){ System.out.println(\"======初始化A......\"); } public String getNameA() { return nameA; } public void setNameA(String nameA) { this.nameA = nameA; } public int getAgeA() { return ageA; } public void setAgeA(int ageA) { this.ageA = ageA; } public B getB() { return b; } public void setB(B b) { this.b = b; }}

return b对象，singletonObject接收

: ObjectFactory

beanFactory.preInstantiateSingletons()

doGetBean执行完毕

new ClassPathXmlApplicationContext()

this.beanFactory.getBean(resolvedName)执行完毕，bean接收返回b对象

return beanInstance

返回构造的对象

返回对象a

this.beanFactory.getBean(resolvedName)执行完毕

a的属性注入完毕，继续处理a

Spring版本：5.2.4.RELEASExml配置：<?xml version=\"1.0\" encoding=\"UTF-8\"?><beans xmlns=\"http://www.springframework.org/schema/beans\"       xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\"       xsi:schemaLocation=\"http://www.springframework.org/schema/beans                http://www.springframework.org/schema/beans/spring-beans.xsd\">    <bean id=\"a\" class=\"com.spring.debug.l3.cache.bean.A\">        <property name=\"b\" ref=\"b\" />    </bean>    <bean id=\"b\" class=\"com.spring.debug.l3.cache.bean.B\" >        <property name=\"a\" ref=\"a\" />    </bean></beans>测试代码        ApplicationContext applicationContext = new ClassPathXmlApplicationContext(\"spring/3L-cache-configration.xml\");        A a = (A) applicationContext.getBean(\"a\");        B b = (B) applicationContext.getBean(\"b\");

ClientSpringL3Cache

AbstractAutowireCapableBeanFactory

将b对象从三级缓存删除放入到一级缓存

return a对象，sharedInstance接收

applyPropertyValuess执行完毕

getSingleton执行完毕

addSingleton执行完毕

ctor.newInstance(argsWithDefaultValues)

return Object

从二级缓存中获取a对象并返回

至此，a、b对象已经放在一级缓存