Spring DefaultListableBeanFactory

Spring的各类Ioc容器中DefaultListableBeanFactory算是最重要的一个之一，能与BeanFactory媲美；

DefalutListableBeanFactory中定义了容器的重要属性，其实就是那几个重要的Map

/** Map from serialized id to factory instance */
	private static final Map<String, Reference<DefaultListableBeanFactory>> serializableFactories =
			new ConcurrentHashMap<String, Reference<DefaultListableBeanFactory>>();

/** Map from dependency type to corresponding autowired value */
	private final Map<Class<?>, Object> resolvableDependencies = new HashMap<Class<?>, Object>();

/** Map of bean definition objects, keyed by bean name */
	private final Map<String, BeanDefinition> beanDefinitionMap = new ConcurrentHashMap<String, BeanDefinition>();

/** Map of singleton bean names keyed by bean class */
	private final Map<Class<?>, String[]> singletonBeanNamesByType = new ConcurrentHashMap<Class<?>, String[]>();

/** Map of non-singleton bean names keyed by bean class */
	private final Map<Class<?>, String[]> nonSingletonBeanNamesByType = new ConcurrentHashMap<Class<?>, String[]>();

还有一个重要的方法，它是实现BeanDifinition注册的；

//---------------------------------------------------------------------
	// Implementation of BeanDefinitionRegistry interface
	//---------------------------------------------------------------------

	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);
			}
		}

		synchronized (this.beanDefinitionMap) {
			Object oldBeanDefinition = this.beanDefinitionMap.get(beanName);
			if (oldBeanDefinition != null) {
				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 {
				this.beanDefinitionNames.add(beanName);
				this.frozenBeanDefinitionNames = null;
			}
			this.beanDefinitionMap.put(beanName, beanDefinition);

			resetBeanDefinition(beanName);
		}
	}

不过一般项目中不会直接使用这个Ioc容器，而是使用ApplicationContext的相关子类；ApplicationContext的子类通过持有（也继承）一个BeanFactory间接的成为一个Ioc容器；并且提供比DefaultListabelBeanFactory更多的功能；持有的方式如下：

@Override
	protected final void refreshBeanFactory() throws BeansException {
		if (hasBeanFactory()) {
			destroyBeans();
			closeBeanFactory();
		}
		try {
			DefaultListableBeanFactory beanFactory = createBeanFactory();
			beanFactory.setSerializationId(getId());
			customizeBeanFactory(beanFactory);
			loadBeanDefinitions(beanFactory);
			synchronized (this.beanFactoryMonitor) {
				this.beanFactory = beanFactory;
			}
		}
		catch (IOException ex) {
			throw new ApplicationContextException("I/O error parsing bean definition source for " + getDisplayName(), ex);
		}
	}

上面的这段代码是AbstractRefreshableApplicationContext的重写方法；AbstractRefreshableApplicationContext持有的是DefaultListableBeanFactory的引用；