Spring DI源码跟踪小记

• 1、开始 AbstractBeanFactory.getBean()

public Object getBean(String name) throws BeansException {
    return this.doGetBean(name, (Class)null, (Object[])null, false);
}

protected <T> T doGetBean(String name, Class<T> requiredType, final Object[] args, boolean typeCheckOnly) throws BeansException {
    final String beanName = this.transformedBeanName(name);
    Object sharedInstance = this.getSingleton(beanName);
    Object bean;
    if (sharedInstance != null && args == null) {
        // ... ...
    } else {
        // ... ...
        // ... ...
        if (mbd.isSingleton()) {
            sharedInstance = this.getSingleton(beanName, new ObjectFactory<Object>() {
                public Object getObject() throws BeansException {
                    try {
                        // 创建bean
                        return AbstractBeanFactory.this.createBean(beanName, mbd, args);
                    } catch (BeansException var2) {
                        AbstractBeanFactory.this.destroySingleton(beanName);
                        throw var2;
                    }
                }
            });
            bean = this.getObjectForBeanInstance(sharedInstance, name, beanName, mbd);
        } else if (mbd.isPrototype()) {
            // ... ...
        } else {
            // ... ...
            } catch (IllegalStateException var20) {
                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", var20);
            }
        }
    }

    if (requiredType != null && bean != null && !requiredType.isAssignableFrom(bean.getClass())) {
        // ... ...
    } else {
        return bean;
    }
}

• 2、AbstractAutowireCapableBeanFactory#createBean()

protected Object createBean(String beanName, RootBeanDefinition mbd, Object[] args) throws BeanCreationException {
    // ... ...

    Object beanInstance;
    // ... ...

    beanInstance = this.doCreateBean(beanName, mbd, args);
    // ... ...

    return beanInstance;
}

protected Object doCreateBean(final String beanName, final RootBeanDefinition mbd, Object[] args) {
    BeanWrapper instanceWrapper = null;
    if (mbd.isSingleton()) {
        instanceWrapper = (BeanWrapper)this.factoryBeanInstanceCache.remove(beanName);
    }

    if (instanceWrapper == null) {
        // 返回Bean包装器
        instanceWrapper = this.createBeanInstance(beanName, mbd, args);
    }

    // ... ...
    Object exposedObject = bean;

    try {
        // 根据Bean包装器填充Bean实例
        this.populateBean(beanName, mbd, instanceWrapper);
        if (exposedObject != null) {
            // 初始化bean
            exposedObject = this.initializeBean(beanName, exposedObject, mbd);
        }
    } catch (Throwable var17) {
        // ... ...
    }

    // ... ...
    try {
        this.registerDisposableBeanIfNecessary(beanName, bean, mbd);
        return exposedObject;
    } catch (BeanDefinitionValidationException var16) {
        throw new BeanCreationException(mbd.getResourceDescription(), beanName, "Invalid destruction signature", var16);
    }
}

protected BeanWrapper createBeanInstance(String beanName, RootBeanDefinition mbd, Object[] args) {
    Class beanClass = this.resolveBeanClass(mbd, beanName, new Class[0]);
    if (beanClass != null && !Modifier.isPublic(beanClass.getModifiers()) && !mbd.isNonPublicAccessAllowed()) {
        // ... ...
    } else if (mbd.getFactoryMethodName() != null) {
        return this.instantiateUsingFactoryMethod(beanName, mbd, args);
    } else {
        // 实例化Bean
        if (resolved) {
            return autowireNecessary ? this.autowireConstructor(beanName, mbd, (Constructor[])null, (Object[])null) : this.instantiateBean(beanName, mbd);
        } else {
            Constructor[] ctors = this.determineConstructorsFromBeanPostProcessors(beanClass, beanName);
            return ctors == null && mbd.getResolvedAutowireMode() != 3 && !mbd.hasConstructorArgumentValues() && ObjectUtils.isEmpty(args) ? this.instantiateBean(beanName, mbd) : this.autowireConstructor(beanName, mbd, ctors, args);
        }
    }
}

protected BeanWrapper instantiateBean(final String beanName, final RootBeanDefinition mbd) {
    try {
        Object beanInstance;
        // 实例化Bean
        if (System.getSecurityManager() != null) {
            beanInstance = AccessController.doPrivileged(new PrivilegedAction<Object>() {
                public Object run() {
                    return AbstractAutowireCapableBeanFactory.this.getInstantiationStrategy().instantiate(mbd, beanName, AbstractAutowireCapableBeanFactory.this);
                }
            }, this.getAccessControlContext());
        } else {
            beanInstance = this.getInstantiationStrategy().instantiate(mbd, beanName, this);
        }
        // 返回Bean包装器
        BeanWrapper bw = new BeanWrapperImpl(beanInstance);
        this.initBeanWrapper(bw);
        return bw;
    } catch (Throwable var6) {
        throw new BeanCreationException(mbd.getResourceDescription(), beanName, "Instantiation of bean failed", var6);
    }
}

总结：
1、调用 AbstractBeanFactory获取Bean
2、跳到 AbstractAutowireCapableBeanFactory.createBean()
3、调用 createBeanInstance 创建Bean包装器 BeanWrapper
4、再使用BeanWrapper填充Bean
5、再使用initializeBean 初始化Bean 然后返回

最后

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