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Spring之IoC

  1. Ioc（控制反转）原理
  2. 源码分析（自底向上）
    1. DefaultSingletonBeanRegistry
    2. FactoryBeanRegistrySupport
    3. AbstractBeanFactory
  3. Bean的三层缓存
  4. BeanDefinition
    1. 获取和构建

Ioc（控制反转）原理

工厂方法+反射

Spring通过IoC容器加载外部资源

DI：在系统运行过程中，动态的向某个对象提供它所需的对象

源码分析（自底向上）

DefaultSingletonBeanRegistry

singletonObjects，只有2个方法可以向其增加

earlySingletonObjects，只有1个方法可以向其增加，代码如下

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private final Map<String, Object> singletonObjects = new ConcurrentHashMap<>(256);
private final Map<String, Object> earlySingletonObjects = new ConcurrentHashMap<>(16);

@Nullable
protected Object getSingleton(String beanName, boolean allowEarlyReference) {
    // Quick check for existing instance without full singleton lock
    Object singletonObject = this.singletonObjects.get(beanName);
    if (singletonObject == null && isSingletonCurrentlyInCreation(beanName)) {
        singletonObject = this.earlySingletonObjects.get(beanName);
        if (singletonObject == null && allowEarlyReference) {
            synchronized (this.singletonObjects) {
                // Consistent creation of early reference within full singleton lock
                singletonObject = this.singletonObjects.get(beanName);
                if (singletonObject == null) {
                    singletonObject = this.earlySingletonObjects.get(beanName);
                    if (singletonObject == null) {
                        ObjectFactory<?> singletonFactory = this.singletonFactories.get(beanName);
                        if (singletonFactory != null) {
                            singletonObject = singletonFactory.getObject();
                            this.earlySingletonObjects.put(beanName, singletonObject);  //【新创建的bean会先放到early里】
                            this.singletonFactories.remove(beanName);
                        }
                    }
                }
            }
        }
    }
    return singletonObject;
}

FactoryBeanRegistrySupport

核心方法getObjectFromFactoryBean，由FactoryBean创建的Bean单独放个缓存

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Map<String, Object> factoryBeanObjectCache = new ConcurrentHashMap<>(16);

Object getObjectFromFactoryBean(FactoryBean<?> factory, String beanName, boolean shouldPostProcess)

AbstractBeanFactory

Bean的三层缓存

主要解决循环依赖

BeanDefinition

获取和构建

主逻辑ClassPathBeanDefinitionScanner#doScan

ClassPathScanningCandidateComponentProvider#scanCandidateComponents

ClassPathBeanDefinitionScanner#postProcessBeanDefinition

AnnotationConfigUtils#processCommonDefinitionAnnotations(AnnotatedBeanDefinition, AnnotatedTypeMetadata)

最后注册到BeanDefinitionRegistry

  技术 / Java
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