Spring bean 源碼 --- BeanFactory

1、 Bean 的生命週期

 * <ol>
 * <li>BeanNameAware's {@code setBeanName}
 * <li>BeanClassLoaderAware's {@code setBeanClassLoader}
 * <li>BeanFactoryAware's {@code setBeanFactory}
 * <li>EnvironmentAware's {@code setEnvironment}
 * <li>EmbeddedValueResolverAware's {@code setEmbeddedValueResolver}
 * <li>ResourceLoaderAware's {@code setResourceLoader}
 * (only applicable when running in an application context)
 * <li>ApplicationEventPublisherAware's {@code setApplicationEventPublisher}
 * (only applicable when running in an application context)
 * <li>MessageSourceAware's {@code setMessageSource}
 * (only applicable when running in an application context)
 * <li>ApplicationContextAware's {@code setApplicationContext}
 * (only applicable when running in an application context)
 * <li>ServletContextAware's {@code setServletContext}
 * (only applicable when running in a web application context)
 * <li>{@code postProcessBeforeInitialization} methods of BeanPostProcessors
 * <li>InitializingBean's {@code afterPropertiesSet}
 * <li>a custom init-method definition
 * <li>{@code postProcessAfterInitialization} methods of BeanPostProcessors
 * </ol>
 *
 * <p>On shutdown of a bean factory, the following lifecycle methods apply:
 * <ol>
 * <li>{@code postProcessBeforeDestruction} methods of DestructionAwareBeanPostProcessors
 * <li>DisposableBean's {@code destroy}
 * <li>a custom destroy-method definition
 * </ol>

 這個是Bean 運行的生命週期。

   ?  這個不太明白，後續補上。

/**
	 * Used to dereference a {@link FactoryBean} instance and distinguish it from
	 * beans <i>created</i> by the FactoryBean. For example, if the bean named
	 * {@code myJndiObject} is a FactoryBean, getting {@code &myJndiObject}
	 * will return the factory, not the instance returned by the factory.
	 */

String FACTORY_BEAN_PREFIX = "&";

  ？通過name 進行實例化對象。

Object getBean(String name) throws BeansException;

？ 這個方法添加指定實例化bean的類型。

<T> T getBean(String name, Class<T> requiredType) throws BeansException;

？這個通過指定實例化的構造函數參數。

Object getBean(String name, Object... args) throws BeansException;

？通過類型進行匹配進行實例化，這個無參構造函數進行實例化。

<T> T getBean(Class<T> requiredType) throws BeansException;

？通過匹配的類型，構造函數進行實例化。

<T> T getBean(Class<T> requiredType, Object... args) throws BeansException;

？構造一個類型提供器。

<T> ObjectProvider<T> getBeanProvider(Class<T> requiredType);

  這個看下其實現,發現內部也是進行實例化，進行了一層的封裝，暫不清楚爲啥會在進行封裝一個這個類。

@Override
	public <T> ObjectProvider<T> getBeanProvider(Class<T> requiredType) {
		return new ObjectProvider<T>() {
			@Override
			public T getObject() throws BeansException {
				return getBean(requiredType);
			}
			@Override
			public T getObject(Object... args) throws BeansException {
				return getBean(requiredType, args);
			}
			@Override
			@Nullable
			public T getIfAvailable() throws BeansException {
				try {
					return getBean(requiredType);
				}
				catch (NoUniqueBeanDefinitionException ex) {
					throw ex;
				}
				catch (NoSuchBeanDefinitionException ex) {
					return null;
				}
			}
			@Override
			@Nullable
			public T getIfUnique() throws BeansException {
				try {
					return getBean(requiredType);
				}
				catch (NoSuchBeanDefinitionException ex) {
					return null;
				}
			}
		};
	}

  看ObjectProvider 類 

/**
 * A variant of {@link ObjectFactory} designed specifically for injection points,
 * allowing for programmatic optionality and lenient not-unique handling.
 */

  在這個類中提供了這個方法

@Override
	default Iterator<T> iterator() {
		return stream().iterator();
	}

說明通過這類可以遍歷處理多個實例。而BeanFactory 的其他方法都是返回一個實例對象。這裏加載多個相同類的實例provider。

從註釋可以發現這個是5.1 增加的方法。