【Spring Framework 深入】—— IoC容器初始化 -> BeanDefinition的注册

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IoC容器初始化的最后一步，想容器中注册完成解析得到的BeanDefinition。
方法调用流程图：
这里写图片描述

入口函数

DefaultBeanDefinitionDocumentReader.java

BeanDefinitionReaderUtils.javapublic static void registerBeanDefinition(            BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry)            throws BeanDefinitionStoreException {        // Register bean definition under primary name.        String beanName = definitionHolder.getBeanName();        registry.registerBeanDefinition(beanName, definitionHolder.getBeanDefinition());        // Register aliases for bean name, if any.        String[] aliases = definitionHolder.getAliases();        if (aliases != null) {            for (String alias : aliases) {                registry.registerAlias(beanName, alias);            }        }    }

可以看到委托给了registry.registerBeanDefinition()，BeanDefinitionRegistry 是一个接口，定义了注册BeanDefinition的行为。这里的registry实际上是容器本身DefaultListableBeanFactory。

DefaultListableBeanFactory.javaprivate final Map<String, BeanDefinition> beanDefinitionMap = new ConcurrentHashMap<String, BeanDefinition>(256);//---------------------------------------------------------------------// Implementation of BeanDefinitionRegistry interface//---------------------------------------------------------------------    @Override    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 ex) {                throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName,                        "Validation of bean definition failed", ex);            }        }        BeanDefinition oldBeanDefinition;        oldBeanDefinition = this.beanDefinitionMap.get(beanName);        //若存在旧值，则要考虑是否允许覆盖        if (oldBeanDefinition != null) {            if (!isAllowBeanDefinitionOverriding()) {                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)) {                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);        }        //不存在旧值        else {            //Check whether this factory's bean creation phase already started,             //i.e. whether any bean has been marked as created in the meantime.            //检查factory's bean creation phase是否已经开始，若是，则需要同步            if (hasBeanCreationStarted()) {                // Cannot modify startup-time collection elements anymore (for stable iteration)                synchronized (this.beanDefinitionMap) {                    //注册过程                    this.beanDefinitionMap.put(beanName, beanDefinition);                    List<String> updatedDefinitions = new ArrayList<String>(this.beanDefinitionNames.size() + 1);                    updatedDefinitions.addAll(this.beanDefinitionNames);                    updatedDefinitions.add(beanName);                    this.beanDefinitionNames = updatedDefinitions;                    if (this.manualSingletonNames.contains(beanName)) {                        Set<String> updatedSingletons = new LinkedHashSet<String>(this.manualSingletonNames);                        updatedSingletons.remove(beanName);                        this.manualSingletonNames = updatedSingletons;                    }                }            }            else {                // Still in startup registration phase                //注册过程                this.beanDefinitionMap.put(beanName, beanDefinition);                this.beanDefinitionNames.add(beanName);                this.manualSingletonNames.remove(beanName);            }            this.frozenBeanDefinitionNames = null;        }        if (oldBeanDefinition != null || containsSingleton(beanName)) {            resetBeanDefinition(beanName);        }    }

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