Spring技術內幕筆記(3)——BeanDefinition在IOC容器中註冊

org.springframework.beans.factory.support.DefaultListableBeanFactory#registerBeanDefinition

 public void registerBeanDefinition(String beanName, BeanDefinition beanDefinition) throws BeanDefinitionStoreException {
        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 var7) {
                throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName, "Validation of bean definition failed", var7);
            }
        }

        BeanDefinition oldBeanDefinition;
		//對註冊過程加鎖，保證數據一致性
        synchronized(this.beanDefinitionMap) {
            oldBeanDefinition = (BeanDefinition)this.beanDefinitionMap.get(beanName);
			//判斷是否已經有同名的beandefinition已經在IOC容器中了，如果有，同時又不可以覆蓋，就報錯
            if (oldBeanDefinition != null) {
                if (!this.allowBeanDefinitionOverriding) {
                    throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName, "Cannot register bean definition [" + beanDefinition + "] for bean '" + beanName + "': There is already [" + oldBeanDefinition + "] bound.");
                }

                if (this.logger.isInfoEnabled()) {
                    this.logger.info("Overriding bean definition for bean '" + beanName + "': replacing [" + oldBeanDefinition + "] with [" + beanDefinition + "]");
                }
            } else {
			//這是註冊BeanDefinition的過程，把bean的名字存入到beanDefinitionNames中，同時存入beanDefinitionMap中
                this.beanDefinitionNames.add(beanName);
                this.frozenBeanDefinitionNames = null;
            }

            this.beanDefinitionMap.put(beanName, beanDefinition);
        }

        if (oldBeanDefinition != null || this.containsSingleton(beanName)) {
            this.resetBeanDefinition(beanName);
        }

    }