Spring bean的生命周期

学习spring源码主框架，从源码角度开发学习Spring bean的生命周期。

spring创建bean方法

org.springframework.beans.factory.support.AbstractBeanFactory#getBean(java.lang.String, java.lang.Class )

public  T getBean(String name, Class requiredType) throws BeansException {
        //doGetBean是获取bean的真实方法
        return doGetBean(name, requiredType, null, false);
    }

真正执行spring创建bean方法doGetBean

org.springframework.beans.factory.support.AbstractBeanFactory#doGetBean

protected  T doGetBean(
            final String name, final Class requiredType, final Object[] args, boolean typeCheckOnly)
            throws BeansException {
        //获取的beanname可能是重命名后的，这个获取原始的beanname，这里做别名解析
        final String beanName = transformedBeanName(name);
        Object bean;

        //先从spring缓存池中获取bean，这里是解决循环依赖的根本
        Object sharedInstance = getSingleton(beanName);
        if (sharedInstance != null && args == null) {
            if (logger.isDebugEnabled()) {
                if (isSingletonCurrentlyInCreation(beanName)) {
                    logger.debug("Returning eagerly cached instance of singleton bean '" + beanName +
                            "' that is not fully initialized yet - a consequence of a circular reference");
                }
                else {
                    logger.debug("Returning cached instance of singleton bean '" + beanName + "'");
                }
            }
            //如果从缓存中获取到bean，进行后续处理。
            bean = getObjectForBeanInstance(sharedInstance, name, beanName, null);
        }

        else {
            //判断当前创建的bean是不是原型的，如果存在循环依赖，则抛异常
            if (isPrototypeCurrentlyInCreation(beanName)) {
                throw new BeanCurrentlyInCreationException(beanName);
            }

            //获取父工厂
            BeanFactory parentBeanFactory = getParentBeanFactory();
            //判断父工厂是否为空，以及当前容器中是否包含bean定义
            if (parentBeanFactory != null && !containsBeanDefinition(beanName)) {
                // Not found -> check parent.
                String nameToLookup = originalBeanName(name);
                //根据构造函数是否有参数，来创建不同的bean
                if (args != null) {
                    // Delegation to parent with explicit args.
                    return (T) parentBeanFactory.getBean(nameToLookup, args);
                }
                else {
                    // No args -> delegate to standard getBean method.
                    return parentBeanFactory.getBean(nameToLookup, requiredType);
                }
            }
            
            if (!typeCheckOnly) {
                markBeanAsCreated(beanName);
            }

            try {
                //合并bean定义，存在抽象父bean定义，专门给子bean做继承的
                final RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
                //检查bean定义的是否为抽象的，如果是则抛出异常
                checkMergedBeanDefinition(mbd, beanName, args);

                //获取bean初始化的前置依赖beanname
                String[] dependsOn = mbd.getDependsOn();
                if (dependsOn != null) {
                    for (String dep : dependsOn) {
                        if (isDependent(beanName, dep)) {
                            throw new BeanCreationException(mbd.getResourceDescription(), beanName,
                                    "Circular depends-on relationship between '" + beanName + "' and '" + dep + "'");
                        }
                        //解析以来的bean，并注册依赖的bean
                        registerDependentBean(dep, beanName);
                        try {
                            //递归调用获取依赖bean
                            getBean(dep);
                        }
                        catch (NoSuchBeanDefinitionException ex) {
                            throw new BeanCreationException(mbd.getResourceDescription(), beanName,
                                    "'" + beanName + "' depends on missing bean '" + dep + "'", ex);
                        }
                    }
                }

                // 创建bean的实例
                if (mbd.isSingleton()) {
                    sharedInstance = getSingleton(beanName, new ObjectFactory