Spring Ioc創建之BeanFactory創建源碼分析

在上篇博客介紹了Ioc容器創建的大概過程，但BeanFactory創建的具體細節沒有說明，好！接下來就讓我們來看下BeanFactory創建的具體細節
首先我們來回顧一下前面內容中介紹過的類AbstractApplicationContext中的方法refresh內部出現的一行代碼
ConfigurableListableBeanFactory beanFactory = this.obtainFreshBeanFactory();
接下來進入到方法obtainFreshBeanFactory中去看看具體實現（該方法的實現也是在類AbstractApplicationContext中）

   protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
        this.refreshBeanFactory();
        ConfigurableListableBeanFactory beanFactory = this.getBeanFactory();
        if(this.logger.isDebugEnabled()) {
            this.logger.debug("Bean factory for " + this.getDisplayName() + ": " + beanFactory);
        }

        return beanFactory;
    }

對於上面的代碼，Emphasis是在方法refreshBeanFactory上，那好！接下來來方法refreshBeanFactory

protected abstract void refreshBeanFactory() throws BeansException, IllegalStateException;

類AbstractApplicationContext中的方法refreshBeanFactory（）是個抽象方法，所以需要到繼承了AbstractApplicationContext類的子類中才有該方法的具體實現

從上圖得知有兩個類·AbstractRefreshableApplicationContext和GenericApplicationContext實現了抽象方法refreshBeanFactory（）
接下來我們就進入到類·AbstractRefreshableApplicationContext,看看方法的具體實現，代碼如下：

protected final void refreshBeanFactory() throws BeansException {

       //如果存在BeanFactory對象，銷燬該對象，並重新創建BeanFactory
        if(this.hasBeanFactory()) {
            this.destroyBeans();
            this.closeBeanFactory();
        }

        try {
            DefaultListableBeanFactory beanFactory = this.createBeanFactory();
            beanFactory.setSerializationId(this.getId());
            this.customizeBeanFactory(beanFactory);

            //解析和登記Bean對象
            this.loadBeanDefinitions(beanFactory);

            Object var2 = this.beanFactoryMonitor;
            synchronized(this.beanFactoryMonitor) {
                this.beanFactory = beanFactory;
            }
        } catch (IOException var5) {
            throw new ApplicationContextException("I/O error parsing bean definition source for " + this.getDisplayName(), var5);
        }
    }

看上面的代碼中，我們看到創建了一個DefaultListableBeanFactory對象beanFactory, 具體過程見下面的代碼

protected DefaultListableBeanFactory createBeanFactory() {
        return new DefaultListableBeanFactory(this.getInternalParentBeanFactory());
    }

兩位有一個方法loadBeanDefinitions(beanFactory)也需要作爲重點分析下,在類AbstractRefreshableApplicationContext中該方法是個*抽象方法：

protected abstract void loadBeanDefinitions(DefaultListableBeanFactory var1) throws BeansException, IOException;

下面的代碼是類AbstractXmlApplicationContext中的該方法loadBeanDefinitions(beanFactory)的實現代碼

  protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) throws BeansException, IOException {
        XmlBeanDefinitionReader beanDefinitionReader = new XmlBeanDefinitionReader(beanFactory);
        beanDefinitionReader.setEnvironment(this.getEnvironment());
        beanDefinitionReader.setResourceLoader(this);
        beanDefinitionReader.setEntityResolver(new ResourceEntityResolver(this));
        this.initBeanDefinitionReader(beanDefinitionReader);
        this.loadBeanDefinitions(beanDefinitionReader);
    }

在上面的代碼中看到下面所示兩個重要操作：

• new XmlBeanDefinitionReader(beanFactory)
• loadBeanDefinitions(beanDefinitionReader)

綜上所述：BeanFactory創建的詳細過程看下面的序列圖：