springIOC源码解析(三)

上回讲到如何通过getBean方法来获取bean,这里感觉流程比较复杂,不知道以我的水平是否能讲清楚,如果有不清楚的地方欢迎讨论

Engine engine = (Engine)beanFactory.getBean("engine");

OK,不多废话追寻源码,这时候会遇到第一个问题XmlBeanFactory中没有getBean(String str)方法,经过查找在其父类AbstractBeanFactory中,

这里有两层逻辑,主要逻辑是首先检查bean是否初始化过,如果是则从以后的信息中获取;如果不是则从bean注册的信息中找到bean 对应的 BeanDefinition,然后创建新的bean

下面我先分析一下普通bean的初始化

protected  T doGetBean(
            final String name, final Class requiredType, final Object[] args, boolean typeCheckOnly)
            throws BeansException {

        final String beanName = transformedBeanName(name);
        Object bean;

        Object sharedInstance = getSingleton(beanName);
        if (sharedInstance != null && args == null) {
            ......
            bean = getObjectForBeanInstance(sharedInstance, name, beanName, null);
        }

        else {
            ......
            if (!typeCheckOnly) {
                //标记一下这个bean被创建过
                markBeanAsCreated(beanName);
            }

            try {
                final RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
                ......
                //查看这个bean是否跟其他bean有依赖关系
                String[] dependsOn = mbd.getDependsOn();
                if (dependsOn != null) {
                    for (String dependsOnBean : dependsOn) {
                        ......
                        //注册依赖bean
                        registerDependentBean(dependsOnBean, beanName);
                        getBean(dependsOnBean);
                    }
                }

                // Create bean instance.
                if (mbd.isSingleton()) {
                    sharedInstance = getSingleton(beanName, new ObjectFactory