Spring 源码阅读 BeanFactory(二) 之registerBeanDefinition方法

BeanFactory内部对BeanDefinition的维护

接上文

@Override
    public void registerBeanDefinition(String beanName, BeanDefinition beanDefinition)
            throws BeanDefinitionStoreException {
        //一些参数校验
        Assert.hasText(beanName, "Bean name must not be empty");
        Assert.notNull(beanDefinition, "BeanDefinition must not be null");

        if (beanDefinition instanceof AbstractBeanDefinition) {
            try {
                ((AbstractBeanDefinition) beanDefinition).validate();
            }
            catch (BeanDefinitionValidationException ex) {
                throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName,
                        "Validation of bean definition failed", ex);
            }
        }

        BeanDefinition oldBeanDefinition;
        //在beanDefinitionMap，根据beanName取得BeanDefinition
        //beanDefinitionMap的定义（Map of bean definition objects, keyed by bean name ）
        oldBeanDefinition = this.beanDefinitionMap.get(beanName);
        if (oldBeanDefinition != null) {//如果已经有该bean
            if (!isAllowBeanDefinitionOverriding()) { //（是否允许ID相同的Bean覆盖，不指定时默认为true）
                throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName,
                        "Cannot register bean definition [" + beanDefinition + "] for bean '" + beanName +
                        "': There is already [" + oldBeanDefinition + "] bound.");
            }
            else if (oldBeanDefinition.getRole() < beanDefinition.getRole()) {
                // e.g. was ROLE_APPLICATION, now overriding with ROLE_SUPPORT or ROLE_INFRASTRUCTURE
                if (this.logger.isWarnEnabled()) {
                    this.logger.warn("Overriding user-defined bean definition for bean '" + beanName +
                            "' with a framework-generated bean definition: replacing [" +
                            oldBeanDefinition + "] with [" + beanDefinition + "]");
                }
            }
            else if (!beanDefinition.equals(oldBeanDefinition)) {//新注入的bean的定义，和旧的不想等
                if (this.logger.isInfoEnabled()) {
                    this.logger.info("Overriding bean definition for bean '" + beanName +
                            "' with a different definition: replacing [" + oldBeanDefinition +
                            "] with [" + beanDefinition + "]");
                }
            }
            else {
                if (this.logger.isDebugEnabled()) {
                    this.logger.debug("Overriding bean definition for bean '" + beanName +
                            "' with an equivalent definition: replacing [" + oldBeanDefinition +
                            "] with [" + beanDefinition + "]");
                }
            }
            this.beanDefinitionMap.put(beanName, beanDefinition);
        }
        else {//否则之前没有定义过同名的Bean
            if (hasBeanCreationStarted()) {//判断BeanFactory 中Bean的创建阶段是否已经开始，这里是已经开始
                // Cannot modify startup-time collection elements anymore (for stable iteration)
                synchronized (this.beanDefinitionMap) {
                    this.beanDefinitionMap.put(beanName, beanDefinition);//先将Bean的定义维护起来
                    List updatedDefinitions = new ArrayList(this.beanDefinitionNames.size() + 1); //注意：这里是一处优化，直接生成期望大小的List
                    updatedDefinitions.addAll(this.beanDefinitionNames);
                    updatedDefinitions.add(beanName);
                    this.beanDefinitionNames = updatedDefinitions;//更新bean定义名字的引用
                    if (this.manualSingletonNames.contains(beanName)) {
                        Set updatedSingletons = new LinkedHashSet(this.manualSingletonNames);
                        updatedSingletons.remove(beanName);
                        this.manualSingletonNames = updatedSingletons;
                    }
                }
            }
            else {//bean的创建阶段还没有开始
                // Still in startup registration phase
                this.beanDefinitionMap.put(beanName, beanDefinition); //直接在维护列表中加入新注册的beanDefinition
                this.beanDefinitionNames.add(beanName);
                this.manualSingletonNames.remove(beanName);
            }
            this.frozenBeanDefinitionNames = null;
        }

        if (oldBeanDefinition != null || containsSingleton(beanName)) { //如果有同名的bean，重置之
            resetBeanDefinition(beanName);
        }
    }