4.1.2Spring源码解析——getBean方法细节之getObjectForBeanInstance(2)

 这里直接上代码,进行相关分析关于getBean方法的整体解析可以看这里getBean方法解析

//name:getBean方法传入的name,beanName:处理过后的name,mbd:null
    protected Object getObjectForBeanInstance(
            Object beanInstance, String name, String beanName, RootBeanDefinition mbd) {
        // Don't let calling code try to dereference the factory if the bean isn't a factory.
        //如果要获取的bean是FactoryBean的引用,并且缓存的对象不是FactoryBean类型。意思就是要获取的bean实现了FactoryBean(属于工厂),但是获取的实例又不是FactoryBean类型的抛错。bean是否是工厂是由它是否实现FactoryBean接口决定的
        if (BeanFactoryUtils.isFactoryDereference(name) && !(beanInstance instanceof FactoryBean)) {
            throw new BeanIsNotAFactoryException(transformedBeanName(name), beanInstance.getClass());
        }
        // 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.
        //如果创建实例不是FactoryBean实例,或者是factoryBean的引用
        if (!(beanInstance instanceof FactoryBean) || BeanFactoryUtils.isFactoryDereference(name)) {
            return beanInstance;
        }
        Object object = null;
        //根据处理过的beanName获取FactoryBean,上面方法传进来的mbd为null
        if (mbd == null) {
            object = getCachedObjectForFactoryBean(beanName);
        }
        //如果获取到的FactoryBean为空,说明这个bean没有实现FactoryBean接口
        if (object == null) {
            // Return bean instance from factory.
            FactoryBean factory = (FactoryBean) beanInstance;
            // Caches object obtained from FactoryBean if it is a singleton.
            //如果bean已经加载过,则获取合并过后的RootBeanDefinition
            if (mbd == null && containsBeanDefinition(beanName)) {
                    //-----------------------------------------合并父类和子类bean------------------------------------------------------//
                mbd = getMergedLocalBeanDefinition(beanName);
                 //-----------------------------------------------------------------------------------------------//
            }
            boolean synthetic = (mbd != null && mbd.isSynthetic());
            object = getObjectFromFactoryBean(factory, beanName, !synthetic);
        }
        return object;
    }

//合并父类和子类bean 的方法

//第一步
 protected RootBeanDefinition getMergedLocalBeanDefinition(String beanName) throws BeansException {
        // Quick check on the concurrent map first, with minimal locking.
        //根据beanName检查是否存在已经合并过的bean
        RootBeanDefinition mbd = this.mergedBeanDefinitions.get(beanName);
        if (mbd != null) {
            return mbd;
        }
        return getMergedBeanDefinition(beanName, getBeanDefinition(beanName));
    }
//第二步
protected RootBeanDefinition getMergedBeanDefinition(String beanName, BeanDefinition bd)
            throws BeanDefinitionStoreException {

        return getMergedBeanDefinition(beanName, bd, null);
    }

//第三步
//containingBd null
    protected RootBeanDefinition getMergedBeanDefinition(
            String beanName, BeanDefinition bd, BeanDefinition containingBd)
            throws BeanDefinitionStoreException {

        synchronized (this.mergedBeanDefinitions) {
            RootBeanDefinition mbd = null;

            // Check with full lock now in order to enforce the same merged instance.
            //通过beanName检查是否已经存在合并过的BeanDefinition
            if (containingBd == null) {
                mbd = this.mergedBeanDefinitions.get(beanName);
            }
            if (mbd == null) {
                //查看是否存在父bean
                if (bd.getParentName() == null) {
                    // Use copy of given root bean definition.
                    //如果不存在父bean,并且是RootBeanDefinition类型的bean,就复制一份RootBeanDefinition并设置给mbd
                    if (bd instanceof RootBeanDefinition) {
                        mbd = ((RootBeanDefinition) bd).cloneBeanDefinition();
                    }
                    //如果不是就把bd中的值复制mbd
                    else {
                        mbd = new RootBeanDefinition(bd);
                    }
                }
                else {
                    // Child bean definition: needs to be merged with parent.
                    //如果这个bean是一个子bean,就需要跟父bean进行合并
                    BeanDefinition pbd;
                    try {
                        //处理父bean的beanName
                        String parentBeanName = transformedBeanName(bd.getParentName());
                        //如果要过去的bean的beanName于父类的不一样,就行合并
                        if (!beanName.equals(parentBeanName)) {
                            //此方法最终调用的还是getMergedBeanDefinition方法
                            pbd = getMergedBeanDefinition(parentBeanName);
                        }
                        else {
                            if (getParentBeanFactory() instanceof ConfigurableBeanFactory) {
                                pbd = ((ConfigurableBeanFactory) getParentBeanFactory()).getMergedBeanDefinition(parentBeanName);
                            }
                            else {
                                throw new NoSuchBeanDefinitionException(bd.getParentName(),
                                        "Parent name '" + bd.getParentName() + "' is equal to bean name '" + beanName +
                                        "': cannot be resolved without an AbstractBeanFactory parent");
                            }
                        }
                    }
                    catch (NoSuchBeanDefinitionException ex) {
                        throw new BeanDefinitionStoreException(bd.getResourceDescription(), beanName,
                                "Could not resolve parent bean definition '" + bd.getParentName() + "'", ex);
                    }
                    // Deep copy with overridden values.
                    //复制合并之后的属性到要返回的RootBeanDefinition中
                    mbd = new RootBeanDefinition(pbd);
                    //将传入的BeanDefinition的属性复制一遍到新的RootBeanDefinition中
                    mbd.overrideFrom(bd);
                }

                // Set default singleton scope, if not configured before.
                //设置是否单利的
                if (!StringUtils.hasLength(mbd.getScope())) {
                    mbd.setScope(RootBeanDefinition.SCOPE_SINGLETON);
                }

                // A bean contained in a non-singleton bean cannot be a singleton itself.
                // Let's correct this on the fly here, since this might be the result of
                // parent-child merging for the outer bean, in which case the original inner bean
                // definition will not have inherited the merged outer bean's singleton status.
//如果外部的bean不是单利的,但是合并之后的bean是单利的那么就将合并之后的按照外部的bean的单利情况来设定
                if (containingBd != null && !containingBd.isSingleton() && mbd.isSingleton()) {
                    mbd.setScope(containingBd.getScope());
                }

                // Only cache the merged bean definition if we're already about to create an
                // instance of the bean, or at least have already created an instance before.
                //保存到缓存中
                if (containingBd == null && isCacheBeanMetadata() && isBeanEligibleForMetadataCaching(beanName)) {
                    this.mergedBeanDefinitions.put(beanName, mbd);
                }
            }

            return mbd;
        }
    }

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