Spring通過配置檔案描述了Bean和Bean之間的依賴關係，通過java反射例項化bean並建立彼此的依賴關係。除此之外還提供了Bean例項的快取，生命週期的管理，bean例項代理，時間釋出，資源裝載等

1 BeanFactory

1.1 簡介

屬於Spring的核心介面，提供了高階IOC的配置機制，BeanFactory是框架的基本設施，面向spring本身，BeanFactory在啟動容器時，並不會初始化配置檔案中定義的Bean，初始化發生在第一次呼叫，對於單例的Bean，BeanFactory會快取在Bean例項，所以在第二次使用時，直接從快取中獲取Bean例項

1.2 BeanFactory繼承體系

1.3 類簡介

1.3.1 BeanFactory

需要管理Bean的生命週期，初始化時需要實現如下介面

 * <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>
 

public interface BeanFactory {
	///對FactoryBean轉義，因為如果使用bean的名字檢索FactoryBean得到的物件是工廠生成的物件
	String FACTORY_BEAN_PREFIX = "&";
	//通過名稱獲取bena例項
	Object getBean(String name) throws BeansException;
	//按照類象獲得Bean，requiredType可以是父類
	<T> T getBean(String name, @Nullable Class<T> requiredType) throws BeansException;
	//按照給定的引數建立bean例項（僅在建立新例項時才應用，而不是在檢索現有例項時應用）
	Object getBean(String name, Object... args) throws BeansException;
	//根據型別獲得Bean
	<T> T getBean(Class<T> requiredType) throws BeansException;
	//按照給定的引數建立對應的Bean（僅在建立新例項時才應用，而不是在檢索現有例項時應用）
	<T> T getBean(Class<T> requiredType, Object... args) throws BeansException;
	//根據name判斷，是否含有某個Bean
	boolean containsBean(String name);
	//是否單例Bean
	boolean isSingleton(String name) throws NoSuchBeanDefinitionException;
	//是否為原型Bean
	boolean isPrototype(String name) throws NoSuchBeanDefinitionException;
	//檢查bean是否和給定的型別匹配
	boolean isTypeMatch(String name, ResolvableType typeToMatch) throws NoSuchBeanDefinitionException;
	boolean isTypeMatch(String name, @Nullable Class<?> typeToMatch) throws NoSuchBeanDefinitionException;
	//獲取Bean的Calss型別
	Class<?> getType(String name) throws NoSuchBeanDefinitionException;
	//獲取Bean別名
	String[] getAliases(String name);

}
 

1.3.2 AutowireCapableBeanFactory 

提供自動裝配bean能力的功能支援，在BeanFactory基礎上實現對已存在例項的管理，預設實現AbstractAutowireCapableBeanFactory，可以使用這個介面整合其它框架,捆綁並填充並不由Spring管理的已存在的例項，通過ApplicationContext的getAutowireCapableBeanFactory介面獲取.定義5種自動裝配策略:不注入AUTOWIRE_NO,使用bean name策略裝配AUTOWIRE_BY_NAME,使用型別裝配策略AUTOWIRE_BY_TYPE,使用構造器裝配策略AUTOWIRE_CONSTRUCTOR,自動裝配策略AUTOWIRE_AUTODETECT

1.3.3 HierarchicalBenFactory

父子級聯IOC容器介面，子容器可以訪問父容器中的Bean，但是父容器不能訪問子容器中的Bean，在同一個容器中Bean的id時唯一的，但在父子容器中子容器可以擁有一個和父容器id相同的Bean

public interface HierarchicalBeanFactory extends BeanFactory {

	/**
	 * Return the parent bean factory, or {@code null} if there is none.
	 */
	@Nullable
	BeanFactory getParentBeanFactory();

	/**
	 * Return whether the local bean factory contains a bean of the given name,
	 * ignoring beans defined in ancestor contexts.
	 * <p>This is an alternative to {@code containsBean}, ignoring a bean
	 * of the given name from an ancestor bean factory.
	 * @param name the name of the bean to query
	 * @return whether a bean with the given name is defined in the local factory
	 * @see BeanFactory#containsBean
	 */
	boolean containsLocalBean(String name);

}

1.3.4 ConfigurableBeanFactory

增強IOC容器的可定製性，定義了設定類裝載器，屬性編輯器，容器初始化後置處理器，定義的邊界很多，具體的需要檢視API

1.3.5 SingletonBeanRegistry

允許在執行期間向容器註冊單例項Bean

void registerSingleton(String beanName, Object singletonObject);

1.3.6 BeanDefinitionRegistry

配置檔案中每一個<bean>節點都可以通過一個BeanDefinition表示，該介面提供以編碼的形式向容器中註冊Bean，提供了刪除Bean的方法以及獲得BeanDefintion的方法

	void registerBeanDefinition(String beanName, BeanDefinition beanDefinition)
			throws BeanDefinitionStoreException;

	/**
	 * Remove the BeanDefinition for the given name.
	 * @param beanName the name of the bean instance to register
	 * @throws NoSuchBeanDefinitionException if there is no such bean definition
	 */
	void removeBeanDefinition(String beanName) throws NoSuchBeanDefinitionException;

	/**
	 * Return the BeanDefinition for the given bean name.
	 * @param beanName name of the bean to find a definition for
	 * @return the BeanDefinition for the given name (never {@code null})
	 * @throws NoSuchBeanDefinitionException if there is no such bean definition
	 */
	BeanDefinition getBeanDefinition(String beanName) throws NoSuchBeanDefinitionException;

1.3.7 ConfigurableListableBeanFactory

提供bean definition的解析,註冊功能,對單例Bean預載入(解決迴圈依賴問題).

1.3.7.1 設定忽略的依賴關係,註冊找到的特殊依賴

　　　　void ignoreDependencyType(Class<?> type); // 忽略型別

　　　　void ignoreDependencyInterface(Class<?> ifc); // 忽略介面

　　　　void registerResolvableDependency(Class<?> dependencyType, Object autowiredValue);

　　　 boolean isAutowireCandidate(String beanName, DependencyDescriptor descriptor) throws NoSuchBeanDefinitionException;

1.3.7.2 獲取bean定義 (可以訪問屬性值跟構造方法的引數值)

　　　　BeanDefinition getBeanDefinition(String beanName) throws NoSuchBeanDefinitionException;

1.3.7.3 鎖定配置資訊.在呼叫refresh時會使用到.

　　　　void freezeConfiguration();

　　　　boolean isConfigurationFrozen();

1.3.7.4 預載入不是懶載入的單例.用於解決迴圈依賴問題

　　　　void preInstantiateSingletons() throws BeansException;

2 ApplicationContext

2.1 簡介

ApplicationContext是由BeanFactory派生而來的，主要的實現是ClassPathXmlApplicationContext ，FileSystemXmlApplicationContext，XmlWebApplicationContext。面向的是框架開發者，幾乎所有的應用都可以使用ApplicationContext而不是BeanFactory。ClassPathXmlApplicationContext預設從類路徑下載入配置檔案，FileSystemXmlApplicationContext預設從系統檔案中載入配置檔案。XmlWebApplicationContext預設從相對於Web根目錄下載入配置檔案ApplocationContext在初始化應用上下文容器時，會初始化所有單例Bean。

2.2 繼承體系

2.3 類簡介

2.3.1 ApplicationContext

訪問應用程式元件的Bean工廠方法。繼承自ListableBeanFactory，提供如下功能：1. 以通用的方式載入檔案資源的能力。2. 將事件釋出到註冊監聽器的功能。3. 解析訊息的能力，支援國際化。4. 從父上下文繼承

public interface ApplicationContext extends EnvironmentCapable, ListableBeanFactory, HierarchicalBeanFactory,
		MessageSource, ApplicationEventPublisher, ResourcePatternResolver {

	省略部分程式碼
	//獲得父應用上下文容器
	ApplicationContext getParent();

	//獲得自動裝配Bean能力
	AutowireCapableBeanFactory getAutowireCapableBeanFactory() throws IllegalStateException;

}

2.3.2 ApplicationEventPublisher

使容器具有釋出應用上下文事件的功能，包括容器的啟動，關閉事件等，凡是實現了ApplicationListener事件監聽介面的Bean都能夠接收到容器事件並對該事件進行處理。在ApplicationContext抽象實現類AbstractApplicationContext中存在ApplicationEventMulticaster負責儲存所有的監聽器並在事件發生時通知監聽器

public interface ApplicationEventPublisher {

	//通知該應用中註冊的匹配的事件監聽器，事件有可能是框架事件也有可能是特定的應用程式事件
	default void publishEvent(ApplicationEvent event) {
		publishEvent((Object) event);
	}
	//向監聽器通知事件
	void publishEvent(Object event);

}

2.3.3 MessageSource

為應用提供i18n國際化訊息訪問的功能

2.3.4 LifeCycle

主要提供了start() & stop()兩個方法，主要用於控制非同步處理過程，在具體使用時該介面需要同時被ApplicationContext和具體的Bean實現，ApplicationContext會將start/stop資訊傳遞給該容器中所有實現了該介面的Bean，達到控制和任務排程等目的

2.3.5 ConfigurableApplicationContext

擴充套件了ApplicationContext，主要新增了兩個方法refresh和close，讓容器具有重新整理，關閉應用上下文的能力。在應用上下文關閉的情況下，呼叫refresh可以啟動應用上下文，在已經啟動的情況下，呼叫refresh可以清除應用上下文的快取並重新載入配置資訊。close關閉應用上下文

	/**
	 * Load or refresh the persistent representation of the configuration,
	 * which might an XML file, properties file, or relational database schema.
	 * <p>As this is a startup method, it should destroy already created singletons
	 * if it fails, to avoid dangling resources. In other words, after invocation
	 * of that method, either all or no singletons at all should be instantiated.
	 * @throws BeansException if the bean factory could not be initialized
	 * @throws IllegalStateException if already initialized and multiple refresh
	 * attempts are not supported
	 */
	void refresh() throws BeansException, IllegalStateException;

	/**
	 * Close this application context, releasing all resources and locks that the
	 * implementation might hold. This includes destroying all cached singleton beans.
	 * <p>Note: Does <i>not</i> invoke {@code close} on a parent context;
	 * parent contexts have their own, independent lifecycle.
	 * <p>This method can be called multiple times without side effects: Subsequent
	 * {@code close} calls on an already closed context will be ignored.
	 */
	@Override
	void close();

3 BeanFactory & ApplicationContext

BeanFactory：面向的是Spring，屬於Spring的基礎設施，是Bean集合的工廠類，其中包含了各種Bean的定義，客戶端請求時將對應的Bean例項化，快取所有單例項的Bean。生成協作類之間的關鍵即解決類之間的依賴關係，還包含了Bean生命週期的控制，預設實現是DefalutListableBeanFactory。在首次使用Bean的時候會初始化Bean

ApplicationContext：面向的是Spring應用的，ApplicationContext擴充套件於BeanFactory，所以它具有BeanFactory所有的功能，除此之外ApplicationContext提供：1. 以通用的方式載入檔案資源的能力。2. 將事件釋出到註冊監聽器的功能。3. 解析訊息的能力，支援國際化。4. 從父上下文繼承的特性。在容器啟動時，會建立所有單例項的Bean。預設實現有ClassPathXmlAC，FileSystemXmlAC，WebXmlAC

4 WebApplicationContext

適用於Web應用，預設從相對於Web根目錄的路徑中載入配置檔案並完成初始化。WebApplicationContext中可以獲得ServletContext的引用。這個Web應用上下文作為屬性放在ServletContext中，一般web應用能夠訪問Spring應用上下文。可以通過WebApplicationContextUtils.getWebApplicationContext(ServletContext sc )從ServletContext中獲取Spring應用上下文（WebApplicationContext）

public interface WebApplicationContext extends ApplicationContext {

	/**
	 * Context attribute to bind root WebApplicationContext to on successful startup.
	 * <p>Note: If the startup of the root context fails, this attribute can contain
	 * an exception or error as value. Use WebApplicationContextUtils for convenient
	 * lookup of the root WebApplicationContext.
	 * @see org.springframework.web.context.support.WebApplicationContextUtils#getWebApplicationContext
	 * @see org.springframework.web.context.support.WebApplicationContextUtils#getRequiredWebApplicationContext
	 */
	String ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE = WebApplicationContext.class.getName() + ".ROOT";

	/**
	 * Scope identifier for request scope: "request".
	 * Supported in addition to the standard scopes "singleton" and "prototype".
	 */
	String SCOPE_REQUEST = "request";

	/**
	 * Scope identifier for session scope: "session".
	 * Supported in addition to the standard scopes "singleton" and "prototype".
	 */
	String SCOPE_SESSION = "session";

	/**
	 * Scope identifier for the global web application scope: "application".
	 * Supported in addition to the standard scopes "singleton" and "prototype".
	 */
	String SCOPE_APPLICATION = "application";

	/**
	 * Name of the ServletContext environment bean in the factory.
	 * @see javax.servlet.ServletContext
	 */
	String SERVLET_CONTEXT_BEAN_NAME = "servletContext";

	/**
	 * Name of the ServletContext/PortletContext init-params environment bean in the factory.
	 * <p>Note: Possibly merged with ServletConfig/PortletConfig parameters.
	 * ServletConfig parameters override ServletContext parameters of the same name.
	 * @see javax.servlet.ServletContext#getInitParameterNames()
	 * @see javax.servlet.ServletContext#getInitParameter(String)
	 * @see javax.servlet.ServletConfig#getInitParameterNames()
	 * @see javax.servlet.ServletConfig#getInitParameter(String)
	 */
	String CONTEXT_PARAMETERS_BEAN_NAME = "contextParameters";

	/**
	 * Name of the ServletContext/PortletContext attributes environment bean in the factory.
	 * @see javax.servlet.ServletContext#getAttributeNames()
	 * @see javax.servlet.ServletContext#getAttribute(String)
	 */
	String CONTEXT_ATTRIBUTES_BEAN_NAME = "contextAttributes";


	/**
	 * Return the standard Servlet API ServletContext for this application.
	 */
	@Nullable
	ServletContext getServletContext();

}

4.1 繼承體系

4.2 類簡介

4.1.1 ConfigurableWebApplicationContext

允許通過配置的方式例項化WebApplicationContext，提供了為Spring設定Web應用上下文以及設定Spring配置檔案地址的功能。配置檔案地址是相對於Web根目錄的地址

	/**
	 * Set the ServletContext for this web application context.
	 * <p>Does not cause an initialization of the context: refresh needs to be
	 * called after the setting of all configuration properties.
	 * @see #refresh()
	 */
	void setServletContext(@Nullable ServletContext servletContext);

	/**
	 * Set the config locations for this web application context in init-param style,
	 * i.e. with distinct locations separated by commas, semicolons or whitespace.
	 * <p>If not set, the implementation is supposed to use a default for the
	 * given namespace or the root web application context, as appropriate.
	 */
	void setConfigLocation(String configLocation);

	/**
	 * Set the config locations for this web application context.
	 * <p>If not set, the implementation is supposed to use a default for the
	 * given namespace or the root web application context, as appropriate.
	 */
	void setConfigLocations(String... configLocations);

4.3 Spring應用上下文和Web應用上下文的關係

WebApplicationContext 中定義了一個常量ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE，在上下文啟動時，WebApplicationContext例項以此鍵存放在ServletContext的屬性列表中，可以通如下語句獲得WebApplicationContext。

servletContext.getAttribute(WebApplicationContext,ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE).它們的關係如下

4.4 Bean在WebApplicationContext中的範圍

之前Bean的範圍有兩個：singleton & prototype，在WebApplicationContext中新增了3個：request，session，global session

4.5 WebApplicationContext初始化

WebApplicationContext需要ServletContext例項，必須在擁有Web容器的前提下才能夠完成啟動工作。可以在web.xml中配置自啟動的servlet或者web容器監聽器，就可以完成spring web應用上下文的啟動。不管是哪種配置都需要使用日誌功能。

4.5.1 配置自啟動servlet

    <!—配置自啟動servlet—>
    <listener>  
        <listener-class>org.springframework.web.context.ContextLoaderServlet</listener-class>  
    </listener>  

    <!—指定配置檔案路徑—>
    <context-param>  
        <param-name>contextConfigLocation</param-name>  
        <param-value>/WEB-INF/applicationContext.xml，/WEB-INF/applicationContextd.xml</param-value>  
    </context-param> 

4.5.2 配置web容器監聽器

    <!—配置web容器監聽器—>
    <listener>  
        <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>  
    </listener>  

    <!—指定配置檔案路徑—>
    <context-param>  
        <param-name>contextConfigLocation</param-name>  
        <param-value>classpath:spring/applicationContext.xml</param-value>  
    </context-param>