spring源码（8）注册解析的BeanDefinition

对于配置文件解析完之后，我们得到了beanDefinition。下一步就是注册。 同样，注册操作委托给BeanDefinitionReaderUtils.registerBeanDefinition。

public static void registerBeanDefinition(
            BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry)
            throws BeanDefinitionStoreException {

        //使用beanName做唯一标识注册
        String beanName = definitionHolder.getBeanName();
        registry.registerBeanDefinition(beanName, definitionHolder.getBeanDefinition());
        //注册所有的别名
        String[] aliases = definitionHolder.getAliases();
        if (aliases != null) {
            for (String aliase : aliases) {
                registry.registerAlias(beanName, aliase);
            }
        }
    }
           

一、使用beanName做唯一标识注册

对于BeanDefinition的注册，spring将beanName，放入list集合beanDefinitionNames。BeanDefinition放入Map集合beanDefinitionMap中。

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;

        //对beanDefinitionMap增加同步操作
        synchronized (this.beanDefinitionMap) {
            oldBeanDefinition = this.beanDefinitionMap.get(beanName);
            if (oldBeanDefinition != null) {
                //如果配置了bean不允许被覆盖，则抛出异常
                if (!this.allowBeanDefinitionOverriding) {
                    throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName,
                            "Cannot register bean definition [" + beanDefinition + "] for bean '" + beanName +
                            "': There is already [" + oldBeanDefinition + "] bound.");
                }
                else {
                    if (this.logger.isInfoEnabled()) {
                        this.logger.info("Overriding bean definition for bean '" + beanName +
                                "': replacing [" + oldBeanDefinition + "] with [" + beanDefinition + "]");
                    }
                }
            }
            else {
                //记录BeanName
                this.beanDefinitionNames.add(beanName);
                this.frozenBeanDefinitionNames = null;
            }
            //记录beanDefinition
            this.beanDefinitionMap.put(beanName, beanDefinition);
        }

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

二、注册所有的别名

别名存放在Map集合aliasMap中

public void registerAlias(String name, String alias) {
        Assert.hasText(name, "'name' must not be empty");
        Assert.hasText(alias, "'alias' must not be empty");
        //如果alias与beanName相同，删除原有的alias
        if (alias.equals(name)) {
            this.aliasMap.remove(alias);
        }
        else {
            //若不允许覆盖，别名已经被其他bean使用，则抛出异常
            if (!allowAliasOverriding()) {
                String registeredName = this.aliasMap.get(alias);
                if (registeredName != null && !registeredName.equals(name)) {
                    throw new IllegalStateException("Cannot register alias '" + alias + "' for name '" +
                            name + "': It is already registered for name '" + registeredName + "'.");
                }
            }
            //循环检查
            checkForAliasCircle(name, alias);
            this.aliasMap.put(alias, name);
        }
    }