概述

BeanFatory作為Spring的IOC容器主要提供了注冊(cè)Bean和管理依賴(lài)這兩個(gè)功能缀蹄，它的接口包括如下函數(shù)：

BeanFactory.png

BeanFactory and ApplicationContext

實(shí)現(xiàn)

BeanFactory接口的實(shí)現(xiàn)為了實(shí)現(xiàn)注冊(cè)Bean的功能钥飞，需要使用BeanDefinitionRegistry這個(gè)接口，這三者的關(guān)系如圖：

BeanFactoryAndBeanDefinitionRegistry.png

DefaultListableBeanFactory.png

IoC容器的兩個(gè)階段

容器啟動(dòng)階段

• 加載配置
• 分析配置信息
• 裝配到BeanDefinition
• PostProcess

BeanFactoryPostProcessor是容器的擴(kuò)展機(jī)制，可在實(shí)例化階段之前對(duì)BeanDefinition中的信息進(jìn)行修改
如PropertyPlaceHolderConfigurer抠忘，把它聲明為Bean蔫耽，ApplicationContext會(huì)注冊(cè)并應(yīng)用它结耀，將bean配置中的占位符用屬性文件中的值替換

Bean實(shí)例化階段

• 實(shí)例化對(duì)象
• 裝配依賴(lài)
• 生命周期回調(diào)
• 對(duì)象的其他處理
• 注冊(cè)回調(diào)接口

Bean生命周期

1. 實(shí)例化
   BeanFactory根據(jù)BeanDefinition來(lái)進(jìn)行實(shí)例化，使用策略模式有反射和cglib兩種方式來(lái)實(shí)例化bean匙铡，返回一個(gè)包裹了bean的BeanWrapper图甜，用于第二步設(shè)置屬性
2. 設(shè)置屬性
   BeanWrapperImpl同時(shí)也是繼承了PropertyEditorRegistry，使用PropertyEditor來(lái)轉(zhuǎn)換類(lèi)型慰枕，設(shè)置屬性
3. Aware接口
   BeanFactory: BeanNameAware BeanClassLoaderAware BeanFactoryAware
   ApplicationContext: ResourceLoaderAware ApplicationEventPublisherAware MessageSourceAware ApplicationContextAware(都是ApplicationContext)
4. BeanPostProcessor

public interface BeanPostProcessor {

    /**
     * Apply this BeanPostProcessor to the given new bean instance <i>before</i> any bean
     * initialization callbacks (like InitializingBean's {@code afterPropertiesSet}
     * or a custom init-method). The bean will already be populated with property values.
     * The returned bean instance may be a wrapper around the original.
     * @param bean the new bean instance
     * @param beanName the name of the bean
     * @return the bean instance to use, either the original or a wrapped one; if
     * {@code null}, no subsequent BeanPostProcessors will be invoked
     * @throws org.springframework.beans.BeansException in case of errors
     * @see org.springframework.beans.factory.InitializingBean#afterPropertiesSet
     */
    Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException;

    /**
     * Apply this BeanPostProcessor to the given new bean instance <i>after</i> any bean
     * initialization callbacks (like InitializingBean's {@code afterPropertiesSet}
     * or a custom init-method). The bean will already be populated with property values.
     * The returned bean instance may be a wrapper around the original.
     * <p>In case of a FactoryBean, this callback will be invoked for both the FactoryBean
     * instance and the objects created by the FactoryBean (as of Spring 2.0). The
     * post-processor can decide whether to apply to either the FactoryBean or created
     * objects or both through corresponding {@code bean instanceof FactoryBean} checks.
     * <p>This callback will also be invoked after a short-circuiting triggered by a
     * {@link InstantiationAwareBeanPostProcessor#postProcessBeforeInstantiation} method,
     * in contrast to all other BeanPostProcessor callbacks.
     * @param bean the new bean instance
     * @param beanName the name of the bean
     * @return the bean instance to use, either the original or a wrapped one; if
     * {@code null}, no subsequent BeanPostProcessors will be invoked
     * @throws org.springframework.beans.BeansException in case of errors
     * @see org.springframework.beans.factory.InitializingBean#afterPropertiesSet
     * @see org.springframework.beans.factory.FactoryBean
     */
    Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException;

}

常用場(chǎng)景：1.處理Aware接口 2.生成當(dāng)前對(duì)象的代理（AOP）
ApplicationContextAwareProcessor處理ApplicationContext相關(guān)的各個(gè)Aware接口具则。

用BeanPostProcessor處理Marker接口時(shí)（如Aware接口），其實(shí)這個(gè)接口相當(dāng)于為這個(gè)Bean添加了新的屬性具帮，接口一般包括的函數(shù)只有設(shè)置屬性和獲取屬性博肋，獲取屬性由Bean的Client調(diào)用，設(shè)置屬性的函數(shù)則由BeanPostProcessor調(diào)用來(lái)進(jìn)行設(shè)置蜂厅，所以這種Marker接口一般是在BeanPostProcessor的Before函數(shù)中處理匪凡，緊鄰著B(niǎo)ean實(shí)例化過(guò)程中的設(shè)置屬性（因?yàn)檫@也是設(shè)置屬性的一種，只不過(guò)是所有Bean統(tǒng)一設(shè)置）掘猿。

相對(duì)的病游，使用BeanPostProcessor來(lái)生成proxy時(shí)會(huì)在after函數(shù)中處理，這時(shí)候bean的初始化已經(jīng)完成稠通，可以被代理了衬衬。

4. InitializingBean和init-method
   Bean的生命周期接口和生命周期方法

5. 注冊(cè)銷(xiāo)毀回調(diào)
   以上的設(shè)置都完成之后，如果Bean實(shí)現(xiàn)了DisposableBean接口或者聲明了destroy-method屬性改橘，那么這時(shí)候容器會(huì)為這個(gè)Bean注冊(cè)一個(gè)用于銷(xiāo)毀的回調(diào)滋尉，當(dāng)關(guān)閉容器的時(shí)候，主動(dòng)調(diào)用一個(gè)函數(shù)飞主，來(lái)執(zhí)行bean的銷(xiāo)毀工作狮惜。

ConfigurableBeanFactory
/**
     * Destroy all singleton beans in this factory, including inner beans that have
     * been registered as disposable. To be called on shutdown of a factory.
     * <p>Any exception that arises during destruction should be caught
     * and logged instead of propagated to the caller of this method.
     */
    void destroySingletons();

ConfigurableApplicationContext
    /**
     * Register a shutdown hook with the JVM runtime, closing this context
     * on JVM shutdown unless it has already been closed at that time.
     * <p>This method can be called multiple times. Only one shutdown hook
     * (at max) will be registered for each context instance.
     * @see java.lang.Runtime#addShutdownHook
     * @see #close()
     */
    void registerShutdownHook();

6. 使用

ApplicationContext

• BeanFactoryPostProcessor高诺，BeabPostProcessor等特殊bean的自動(dòng)識(shí)別
• bean實(shí)例的自動(dòng)初始化
• 統(tǒng)一的資源加載策略
• 國(guó)際化的信息支持
• 容器內(nèi)事件發(fā)布

資源加載

問(wèn)題：

1. java.net.URL局限于http,ftp,file等協(xié)議，而資源可以以二進(jìn)制碾篡、字節(jié)流虱而、文件等形式存在于文件系統(tǒng)、classpath开泽、URL定位等地方
2. java.net.URL對(duì)資源的查找和定位沒(méi)有清晰的界限牡拇，返回的形式多種多樣，沒(méi)有統(tǒng)一的抽象

解決：
Resource與ResourceLoader

ClassPathResource class|classLoader#getResourceAsStream
FileSystemResource
UrlResource   UrlConnection#getInputStream
ByteArrayResource
InputStreamResource 

public interface Resource extends InputStreamSource {

    /**
     * Return whether this resource actually exists in physical form.
     * <p>This method performs a definitive existence check, whereas the
     * existence of a {@code Resource} handle only guarantees a
     * valid descriptor handle.
     */
    boolean exists();

    /**
     * Return whether the contents of this resource can be read,
     * e.g. via {@link #getInputStream()} or {@link #getFile()}.
     * <p>Will be {@code true} for typical resource descriptors;
     * note that actual content reading may still fail when attempted.
     * However, a value of {@code false} is a definitive indication
     * that the resource content cannot be read.
     * @see #getInputStream()
     */
    boolean isReadable();

    /**
     * Return whether this resource represents a handle with an open
     * stream. If true, the InputStream cannot be read multiple times,
     * and must be read and closed to avoid resource leaks.
     * <p>Will be {@code false} for typical resource descriptors.
     */
    boolean isOpen();

    /**
     * Return a URL handle for this resource.
     * @throws IOException if the resource cannot be resolved as URL,
     * i.e. if the resource is not available as descriptor
     */
    URL getURL() throws IOException;

    /**
     * Return a URI handle for this resource.
     * @throws IOException if the resource cannot be resolved as URI,
     * i.e. if the resource is not available as descriptor
     */
    URI getURI() throws IOException;

    /**
     * Return a File handle for this resource.
     * @throws IOException if the resource cannot be resolved as absolute
     * file path, i.e. if the resource is not available in a file system
     */
    File getFile() throws IOException;

    /**
     * Determine the content length for this resource.
     * @throws IOException if the resource cannot be resolved
     * (in the file system or as some other known physical resource type)
     */
    long contentLength() throws IOException;

    /**
     * Determine the last-modified timestamp for this resource.
     * @throws IOException if the resource cannot be resolved
     * (in the file system or as some other known physical resource type)
     */
    long lastModified() throws IOException;

    /**
     * Create a resource relative to this resource.
     * @param relativePath the relative path (relative to this resource)
     * @return the resource handle for the relative resource
     * @throws IOException if the relative resource cannot be determined
     */
    Resource createRelative(String relativePath) throws IOException;

    /**
     * Determine a filename for this resource, i.e. typically the last
     * part of the path: for example, "myfile.txt".
     * <p>Returns {@code null} if this type of resource does not
     * have a filename.
     */
    String getFilename();

    /**
     * Return a description for this resource,
     * to be used for error output when working with the resource.
     * <p>Implementations are also encouraged to return this value
     * from their {@code toString} method.
     * @see Object#toString()
     */
    String getDescription();

}
public interface InputStreamSource {

    /**
     * Return an {@link InputStream}.
     * <p>It is expected that each call creates a <i>fresh</i> stream.
     * <p>This requirement is particularly important when you consider an API such
     * as JavaMail, which needs to be able to read the stream multiple times when
     * creating mail attachments. For such a use case, it is <i>required</i>
     * that each {@code getInputStream()} call returns a fresh stream.
     * @return the input stream for the underlying resource (must not be {@code null})
     * @throws IOException if the stream could not be opened
     * @see org.springframework.mail.javamail.MimeMessageHelper#addAttachment(String, InputStreamSource)
     */
    InputStream getInputStream() throws IOException;
}

public interface ResourceLoader {

    /** Pseudo URL prefix for loading from the class path: "classpath:" */
    String CLASSPATH_URL_PREFIX = ResourceUtils.CLASSPATH_URL_PREFIX;


    /**
     * Return a Resource handle for the specified resource.
     * The handle should always be a reusable resource descriptor,
     * allowing for multiple {@link Resource#getInputStream()} calls.
     * <p><ul>
     * <li>Must support fully qualified URLs, e.g. "file:C:/test.dat".
     * <li>Must support classpath pseudo-URLs, e.g. "classpath:test.dat".
     * <li>Should support relative file paths, e.g. "WEB-INF/test.dat".
     * (This will be implementation-specific, typically provided by an
     * ApplicationContext implementation.)
     * </ul>
     * <p>Note that a Resource handle does not imply an existing resource;
     * you need to invoke {@link Resource#exists} to check for existence.
     * @param location the resource location
     * @return a corresponding Resource handle
     * @see #CLASSPATH_URL_PREFIX
     * @see org.springframework.core.io.Resource#exists
     * @see org.springframework.core.io.Resource#getInputStream
     */
    Resource getResource(String location);

    /**
     * Expose the ClassLoader used by this ResourceLoader.
     * <p>Clients which need to access the ClassLoader directly can do so
     * in a uniform manner with the ResourceLoader, rather than relying
     * on the thread context ClassLoader.
     * @return the ClassLoader (only {@code null} if even the system
     * ClassLoader isn't accessible)
     * @see org.springframework.util.ClassUtils#getDefaultClassLoader()
     */
    ClassLoader getClassLoader();

}

DefaultResourceLoader#getResource

(1) 檢查路徑是否以classpath:開(kāi)頭->ClassPathResource
(2) a.通過(guò)Url來(lái)定位資源眼姐，構(gòu)造UrlResource诅迷；b.構(gòu)造ClassPathResource

FileSystemResourceLoader

修改了(2)b構(gòu)造FileSystemResource

ResourcePatternResolver

ResourceLoader的擴(kuò)展，添加了getResources
它的實(shí)現(xiàn)會(huì)委派一個(gè)ResouceLoader來(lái)加載資源

ApplicationContext

繼承了ResourcePatternResolver众旗，它的實(shí)現(xiàn)一般會(huì)繼承一個(gè)AbstractApplicationContext，這個(gè)類(lèi)會(huì)繼承DefaultReosurceLoader趟畏，而且有一個(gè)ResourcePatternResolver的對(duì)象贡歧，通過(guò)自己構(gòu)造。詳見(jiàn)Spring揭秘p91赋秀。