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Spring 源碼解析之DispatcherServlet源碼解析(五)

來(lái)源：程序員人生發(fā)布時(shí)間：2016-06-14 09:25:50 閱讀次數(shù)：2921次

Spring 源碼解析之DispatcherServlet源碼解析(5)

前言

本文需要有前4篇文章的基礎(chǔ)，才能夠清晰易懂，有興趣可以先看看詳細(xì)的流程，這篇文章可以說(shuō)是第1篇文章，也能夠說(shuō)是前4篇文章的的匯總，Spring的全部要求流程都是圍繞著DispatcherServlet進(jìn)行的

類結(jié)構(gòu)圖

Renderings

根據(jù)類的結(jié)構(gòu)來(lái)講DispatcherServlet本身也是繼承了HttpServlet的，所有的要求都是根據(jù)這1個(gè)Servlet來(lái)進(jìn)行轉(zhuǎn)發(fā)的,同時(shí)解釋了為何需要在web.xml進(jìn)行以下配置，由于Spring是基于1個(gè)Servlet來(lái)展開的，固然不需要Servlet也能夠使用Spring

<servlet>  
    <servlet-name>appServlet</servlet-name>  
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>  
    <init-param>  
        <param-name>contextConfigLocation</param-name>  
        <param-value>classpath:spring/spring-servlet.xml</param-value>  
    </init-param>  
    <load-on-startup>1</load-on-startup>  
</servlet>  
<servlet-mapping>  
    <servlet-name>appServlet</servlet-name>  
    <url-pattern>/</url-pattern>  
</servlet-mapping>

1 DispatcherServlet初始化

1.1 DispatcherServlet初始化加載的幾個(gè)bean

protected void initStrategies(ApplicationContext context) {
    //初始化文件上傳處理類
        initMultipartResolver(context);
    //初始化本地化Resolver
        initLocaleResolver(context);
    //初始化主題Resolver
        initThemeResolver(context);
    //初始化1些個(gè)與處理的HandlerMappings
        initHandlerMappings(context);
    //
        initHandlerAdapters(context);
    //初始化異常處理的handler
        initHandlerExceptionResolvers(context);
    //初始化要求路徑轉(zhuǎn)換為ViewName 的Translator
        initRequestToViewNameTranslator(context);
  //初始化ViewResolvers 這個(gè)就是針對(duì)視圖處理的Resolvers 比如jsp處理Resolvers 或freemarker處理Resolvers
        initViewResolvers(context);
    //初始化 主要管理flashmap，比如RedirectAttributes 的屬性會(huì)放到這個(gè)里面，默許使用的是SessionFlashMapManager
        initFlashMapManager(context);
    }

1.2 初始化流程圖

Renderings

1.2.1 HttpServletBean源碼解析

HttpServletBean本身來(lái)講是1個(gè)普通的servlet而已,主要做1些資源的初始化

public abstract class HttpServletBean extends HttpServlet
        implements EnvironmentCapable, EnvironmentAware {

    protected final Log logger = LogFactory.getLog(getClass());

    /**
     * Set of required properties (Strings) that must be supplied as
     * config parameters to this servlet.
     */
    private final Set<String> requiredProperties = new HashSet<String>();

    private ConfigurableEnvironment environment;


    /**
     * Subclasses can invoke this method to specify that this property
     * (which must match a JavaBean property they expose) is mandatory,
     * and must be supplied as a config parameter. This should be called
     * from the constructor of a subclass.
     * <p>This method is only relevant in case of traditional initialization
     * driven by a ServletConfig instance.
     * @param property name of the required property
     */
    protected final void addRequiredProperty(String property) {
        this.requiredProperties.add(property);
    }

    /**
     * Map config parameters onto bean properties of this servlet, and
     * invoke subclass initialization.
     * @throws ServletException if bean properties are invalid (or required
     * properties are missing), or if subclass initialization fails.
     */
    @Override
    public final void init() throws ServletException {
        if (logger.isDebugEnabled()) {
            logger.debug("Initializing servlet '" + getServletName() + "'");
        }

        // Set bean properties from init parameters.
        try {
      //使用Servlet配置的初始化參數(shù)創(chuàng)建1個(gè)PropertyValues對(duì)象,PropertyValues對(duì)象是名值對(duì)的集合, 子類也能夠指定哪些屬性是必須的  
            PropertyValues pvs = new ServletConfigPropertyValues(getServletConfig(), this.requiredProperties);
      //把當(dāng)前的Servlet當(dāng)作1個(gè)Bean, 把Bean的屬性和屬性的存取方法信息放入BeanWrapper對(duì)象  
            BeanWrapper bw = PropertyAccessorFactory.forBeanPropertyAccess(this);
      //注冊(cè)1個(gè)可以在資源和路徑之間進(jìn)行轉(zhuǎn)化的客戶化編輯器，這些資源是這個(gè)Web利用的內(nèi)部資源，例如，1個(gè)文件，1個(gè)圖片等等  
            ResourceLoader resourceLoader = new ServletContextResourceLoader(getServletContext());
            bw.registerCustomEditor(Resource.class, new ResourceEditor(resourceLoader, getEnvironment()));
       //提供給子類機(jī)會(huì)增加更多的客戶化的編輯器，或?qū)eanWrapper進(jìn)行更多的初始化  
            initBeanWrapper(bw);
      //把初始化制定的參數(shù)值賦值到Servlet的屬性中，第2個(gè)參數(shù)true表明疏忽位置屬性  
            bw.setPropertyValues(pvs, true);
        }
        catch (BeansException ex) {
            logger.error("Failed to set bean properties on servlet '" + getServletName() + "'", ex);
            throw ex;
        }

        // Let subclasses do whatever initialization they like.
    //提供給子類的的初始化方法 目前是FrameworkServlet 進(jìn)行了實(shí)現(xiàn)
        initServletBean();

        if (logger.isDebugEnabled()) {
            logger.debug("Servlet '" + getServletName() + "' configured successfully");
        }
    }

    /**
     * Initialize the BeanWrapper for this HttpServletBean,
     * possibly with custom editors.
     * <p>This default implementation is empty.
     * @param bw the BeanWrapper to initialize
     * @throws BeansException if thrown by BeanWrapper methods
     * @see org.springframework.beans.BeanWrapper#registerCustomEditor
     */
    protected void initBeanWrapper(BeanWrapper bw) throws BeansException {
    }


    /**
     * Overridden method that simply returns {@code null} when no
     * ServletConfig set yet.
     * @see #getServletConfig()
     */
    @Override
    public final String getServletName() {
        return (getServletConfig() != null ? getServletConfig().getServletName() : null);
    }

    /**
     * Overridden method that simply returns {@code null} when no
     * ServletConfig set yet.
     * @see #getServletConfig()
     */
    @Override
    public final ServletContext getServletContext() {
        return (getServletConfig() != null ? getServletConfig().getServletContext() : null);
    }


    /**
     * Subclasses may override this to perform custom initialization.
     * All bean properties of this servlet will have been set before this
     * method is invoked.
     * <p>This default implementation is empty.
     * @throws ServletException if subclass initialization fails
     */
    protected void initServletBean() throws ServletException {
    }

    /**
     * {@inheritDoc}
     * @throws IllegalArgumentException if environment is not assignable to
     * {@code ConfigurableEnvironment}.
     */
    @Override
    public void setEnvironment(Environment environment) {
        Assert.isInstanceOf(ConfigurableEnvironment.class, environment);
        this.environment = (ConfigurableEnvironment) environment;
    }

    /**
     * {@inheritDoc}
     * <p>If {@code null}, a new environment will be initialized via
     * {@link #createEnvironment()}.
     */
    @Override
    public ConfigurableEnvironment getEnvironment() {
        if (this.environment == null) {
            this.environment = this.createEnvironment();
        }
        return this.environment;
    }

    /**
     * Create and return a new {@link StandardServletEnvironment}. Subclasses may override
     * in order to configure the environment or specialize the environment type returned.
     */
    protected ConfigurableEnvironment createEnvironment() {
        return new StandardServletEnvironment();
    }


    /**
     * PropertyValues implementation created from ServletConfig init parameters.
     */
   //主要是用來(lái)添加初始化參數(shù)的
    private static class ServletConfigPropertyValues extends MutablePropertyValues {

        /**
         * Create new ServletConfigPropertyValues.
         * @param config ServletConfig we'll use to take PropertyValues from
         * @param requiredProperties set of property names we need, where
         * we can't accept default values requiredProperties 這個(gè)參數(shù)主要是指定初始化時(shí)必須添加的參數(shù)
         * @throws ServletException if any required properties are missing
         */
        public ServletConfigPropertyValues(ServletConfig config, Set<String> requiredProperties)
            throws ServletException {

            Set<String> missingProps = (requiredProperties != null && !requiredProperties.isEmpty()) ?
                    new HashSet<String>(requiredProperties) : null;

            Enumeration<String> en = config.getInitParameterNames();
            while (en.hasMoreElements()) {
                String property = en.nextElement();
                Object value = config.getInitParameter(property);
                addPropertyValue(new PropertyValue(property, value));
                if (missingProps != null) {
                    missingProps.remove(property);
                }
            }

            // Fail if we are still missing properties.
            if (missingProps != null && missingProps.size() > 0) {
                throw new ServletException(
                    "Initialization from ServletConfig for servlet '" + config.getServletName() +
                    "' failed; the following required properties were missing: " +
                    StringUtils.collectionToDelimitedString(missingProps, ", "));
            }
        }
    }

}

1.2.1 FrameworkServlet源碼解析

這里只貼初始化的需要的部份代碼，根據(jù)上面的邏輯，子類實(shí)現(xiàn)了initServletBean()這個(gè)方法進(jìn)行初始化

public abstract class FrameworkServlet extends HttpServletBean implements ApplicationContextAware {

    protected void initFrameworkServlet() throws ServletException {
    }
    //實(shí)現(xiàn)HttpServletBean 的初始化接口
    @Override
    protected final void initServletBean() throws ServletException {
        getServletContext().log("Initializing Spring FrameworkServlet '" + getServletName() + "'");
        if (this.logger.isInfoEnabled()) {
            this.logger.info("FrameworkServlet '" + getServletName() + "': initialization started");
        }
        long startTime = System.currentTimeMillis();

        try {
        //初始化webApplicationContext
            this.webApplicationContext = initWebApplicationContext();
        //這個(gè)是留給子類去實(shí)現(xiàn)的方法，暫時(shí)來(lái)講沒有具體的實(shí)現(xiàn)，主要是留給開發(fā)人員自定義1些特性的時(shí)候
        //這個(gè)時(shí)候WebApplicationContext已被初始化了，也就是1些個(gè)spring的配置文件已被初始化了
            initFrameworkServlet();
        }
        catch (ServletException ex) {
            this.logger.error("Context initialization failed", ex);
            throw ex;
        }
        catch (RuntimeException ex) {
            this.logger.error("Context initialization failed", ex);
            throw ex;
        }

        if (this.logger.isInfoEnabled()) {
            long elapsedTime = System.currentTimeMillis() - startTime;
            this.logger.info("FrameworkServlet '" + getServletName() + "': initialization completed in " +
                    elapsedTime + " ms");
        }
    }

    protected WebApplicationContext initWebApplicationContext() {
    //獲得根的Context對(duì)象，比如說(shuō)我用了Spring boot或注解的方式進(jìn)行初始化，那末這里的Context就是Spring boot或其他的context對(duì)象
        WebApplicationContext rootContext =
                WebApplicationContextUtils.getWebApplicationContext(getServletContext());
        WebApplicationContext wac = null;
    //如果當(dāng)前的webApplicationContext 不等于null
        if (this.webApplicationContext != null) {
            // A context instance was injected at construction time -> use it
            wac = this.webApplicationContext;
      //如果context對(duì)象是ConfigurableWebApplicationContext
            if (wac instanceof ConfigurableWebApplicationContext) {
                ConfigurableWebApplicationContext cwac = (ConfigurableWebApplicationContext) wac;
        //如果ConfigurableWebApplicationContext 不是存活狀態(tài)
                if (!cwac.isActive()) {
                    // The context has not yet been refreshed -> provide services such as
                    // setting the parent context, setting the application context id, etc
          //如果沒有設(shè)置過(guò)parent
                    if (cwac.getParent() == null) {
                        // The context instance was injected without an explicit parent -> set
                        // the root application context (if any; may be null) as the parent
                        cwac.setParent(rootContext);
                    }
          //
                    configureAndRefreshWebApplicationContext(cwac);
                }
            }
        }
        if (wac == null) {
            // No context instance was injected at construction time -> see if one
            // has been registered in the servlet context. If one exists, it is assumed
            // that the parent context (if any) has already been set and that the
            // user has performed any initialization such as setting the context id
      //查詢當(dāng)前的Context，下述有詳細(xì)講授
            wac = findWebApplicationContext();
        }
    //如果沒有找到那末就通過(guò)rootContext 去創(chuàng)建1個(gè)Context對(duì)象
        if (wac == null) {
            // No context instance is defined for this servlet -> create a local one
            wac = createWebApplicationContext(rootContext);
        }
    //如果允許通過(guò)事件通知，那末就直接初始化。通過(guò)事件的通知可以反向的說(shuō)明onRefresh()這個(gè)方法是可以被重復(fù)調(diào)用的，具體分析看下面
        if (!this.refreshEventReceived) {
            // Either the context is not a ConfigurableApplicationContext with refresh
            // support or the context injected at construction time had already been
            // refreshed -> trigger initial onRefresh manually here.
            onRefresh(wac);
        }
    // Publish the context as a servlet context attribute.
  //如果允許publish Context的話那末就把spring context放入到spring的ServletContext中
        if (this.publishContext) {
            String attrName = getServletContextAttributeName();
            getServletContext().setAttribute(attrName, wac);
            if (this.logger.isDebugEnabled()) {
                this.logger.debug("Published WebApplicationContext of servlet '" + getServletName() +
                        "' as ServletContext attribute with name [" + attrName + "]");
            }
        }

        return wac;
    }
  //創(chuàng)建and refresh WebApplicationContext
  protected void configureAndRefreshWebApplicationContext(ConfigurableWebApplicationContext wac) {
    //判斷id
        if (ObjectUtils.identityToString(wac).equals(wac.getId())) {
            // The application context id is still set to its original default value
            // -> assign a more useful id based on available information
            if (this.contextId != null) {
                wac.setId(this.contextId);
            }
            else {
                // Generate default id...
                wac.setId(ConfigurableWebApplicationContext.APPLICATION_CONTEXT_ID_PREFIX +
                        ObjectUtils.getDisplayString(getServletContext().getContextPath()) + "/" + getServletName());
            }
        }

        wac.setServletContext(getServletContext());
        wac.setServletConfig(getServletConfig());
        wac.setNamespace(getNamespace());
    //添加針對(duì)ContextRefreshListener事件的監(jiān)聽
    //ApplicationListener decorator that filters events from a specified event source, invoking its delegate listener for matching ApplicationEvent objects only.
    //看了1下英文，大概是用了decorator（裝潢）模式，具體源碼里面，也只是做了1個(gè)簡(jiǎn)單的裝潢模式，這個(gè)類接受所有的ApplicationEvent事件
        wac.addApplicationListener(new SourceFilteringListener(wac, new ContextRefreshListener()));

        // The wac environment's #initPropertySources will be called in any case when the context
        // is refreshed; do it eagerly here to ensure servlet property sources are in place for
        // use in any post-processing or initialization that occurs below prior to #refresh
        ConfigurableEnvironment env = wac.getEnvironment();
        if (env instanceof ConfigurableWebEnvironment) {
            ((ConfigurableWebEnvironment) env).initPropertySources(getServletContext(), getServletConfig());
        }
    //Post-process the given WebApplicationContext before it is refreshed
    //大概就是說(shuō)，在初始化handlermapping和1些本地化等調(diào)用refresh方法之前處理WebApplicationContext，這個(gè)類沒有具體實(shí)現(xiàn)，開發(fā)者可以自己去處理
        postProcessWebApplicationContext(wac);
    //spring dispatcherServlet初始化的時(shí)候可以指定初始化1些類
        applyInitializers(wac);
    //這個(gè)是重點(diǎn)方法，這里采取了事件的模式進(jìn)行通知，去調(diào)用refresh方法初始化配置
        wac.refresh();
    }
  //初始化spring context的時(shí)候 初始化1些指定需要初始化的類 這些類需要實(shí)現(xiàn)ApplicationContextInitializer 這個(gè)接口才能進(jìn)行調(diào)用
  protected void applyInitializers(ConfigurableApplicationContext wac) {
    //獲得到ServletContext中初始化的類數(shù)組參數(shù)
    //
        String globalClassNames = getServletContext().getInitParameter(ContextLoader.GLOBAL_INITIALIZER_CLASSES_PARAM);
        if (globalClassNames != null) {
      //不斷的去初始化這個(gè)類數(shù)組 以,;\t\n等作為分隔符
            for (String className : StringUtils.tokenizeToStringArray(globalClassNames, INIT_PARAM_DELIMITERS)) {
                this.contextInitializers.add(loadInitializer(className, wac));
            }
        }

        if (this.contextInitializerClasses != null) {
            for (String className : StringUtils.tokenizeToStringArray(this.contextInitializerClasses, INIT_PARAM_DELIMITERS)) {
                this.contextInitializers.add(loadInitializer(className, wac));
            }
        }
    //排序，可以指定這些類的初始化順序，通過(guò)@Order注解來(lái)實(shí)現(xiàn)排序
        AnnotationAwareOrderComparator.sort(this.contextInitializers);
    //初始化
        for (ApplicationContextInitializer<ConfigurableApplicationContext> initializer : this.contextInitializers) {
            initializer.initialize(wac);
        }
    }
  //初始化類，
  private ApplicationContextInitializer<ConfigurableApplicationContext> loadInitializer(
            String className, ConfigurableApplicationContext wac) {
        try {
      //加載這個(gè)類
            Class<?> initializerClass = ClassUtils.forName(className, wac.getClassLoader());
      //判斷是不是實(shí)現(xiàn)了接口ApplicationContextInitializer
            Class<?> initializerContextClass =
                    GenericTypeResolver.resolveTypeArgument(initializerClass, ApplicationContextInitializer.class);
            if (initializerContextClass != null && !initializerContextClass.isInstance(wac)) {
                throw new ApplicationContextException(String.format(
                        "Could not apply context initializer [%s] since its generic parameter [%s] " +
                        "is not assignable from the type of application context used by this " +
                        "framework servlet: [%s]", initializerClass.getName(), initializerContextClass.getName(),
                        wac.getClass().getName()));
            }
      //初始化對(duì)象
            return BeanUtils.instantiateClass(initializerClass, ApplicationContextInitializer.class);
        }
        catch (ClassNotFoundException ex) {
            throw new ApplicationContextException(String.format("Could not load class [%s] specified " +
                    "via 'contextInitializerClasses' init-param", className), ex);
        }
    }
}

上述代碼獲得root Context的時(shí)候可以通過(guò)以下代碼了解到獲得方式，webapp的Context對(duì)象的保存，其實(shí)不過(guò)就是把spring的context放到了ServletContext的1個(gè)屬性中而已

WebApplicationContext rootContext =
    WebApplicationContextUtils.getWebApplicationContext(getServletContext());

public abstract class WebApplicationContextUtils {
  public static WebApplicationContext getWebApplicationContext(ServletContext sc) {
        return getWebApplicationContext(sc, WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE);
    }

    /**
     * Find a custom {@code WebApplicationContext} for this web app.
     * @param sc ServletContext to find the web application context for
     * @param attrName the name of the ServletContext attribute to look for
     * @return the desired WebApplicationContext for this web app, or {@code null} if none
     */
    public static WebApplicationContext getWebApplicationContext(ServletContext sc, String attrName) {
        Assert.notNull(sc, "ServletContext must not be null");
    //通過(guò)從ServletContext 去獲得spring的context對(duì)象
        Object attr = sc.getAttribute(attrName);
        if (attr == null) {
            return null;
        }
        if (attr instanceof RuntimeException) {
            throw (RuntimeException) attr;
        }
        if (attr instanceof Error) {
            throw (Error) attr;
        }
        if (attr instanceof Exception) {
            throw new IllegalStateException((Exception) attr);
        }
        if (!(attr instanceof WebApplicationContext)) {
            throw new IllegalStateException("Context attribute is not of type WebApplicationContext: " + attr);
        }
        return (WebApplicationContext) attr;
    }
}

wac = findWebApplicationContext(); 上述這塊邏輯主要是通過(guò)獲得ContextAttribute的屬性名去ServletContext中獲得Context對(duì)象

protected WebApplicationContext findWebApplicationContext() {
    String attrName = getContextAttribute();
    if (attrName == null) {
      return null;
    }
    WebApplicationContext wac =
        WebApplicationContextUtils.getWebApplicationContext(getServletContext(), attrName);
    if (wac == null) {
      throw new IllegalStateException("No WebApplicationContext found: initializer not registered?");
    }
    return wac;
}

1.2.2 FrameworkServlet 中refresh源碼解析

這里流程比較繁瑣，重點(diǎn)講述1下 wac.refresh(); 這個(gè)方法會(huì)調(diào)用AbstractApplicationContext這里類面的refresh去實(shí)現(xiàn)相應(yīng)的邏輯，這個(gè)類具體的英文解釋（implements common context functionality. Uses the Template Method design pattern）大概意思就是說(shuō)實(shí)現(xiàn)了1些公有的方法，通過(guò)Template Method這類設(shè)計(jì)模式實(shí)現(xiàn)功能，其實(shí)也就是將邏輯放到了AbstractApplicationContext中，然后子類去實(shí)現(xiàn)各種方法。邏輯已由AbstractApplicationContext定好，子類不關(guān)心邏輯

public abstract class AbstractApplicationContext extends DefaultResourceLoader
        implements ConfigurableApplicationContext, DisposableBean {
  //準(zhǔn)備刷新之前調(diào)用    
  protected void prepareRefresh() {
    //記錄開始時(shí)間
        this.startupDate = System.currentTimeMillis();
    //改變狀態(tài)
        this.closed.set(false);
        this.active.set(true);

        if (logger.isInfoEnabled()) {
            logger.info("Refreshing " + this);
        }

        // Initialize any placeholder property sources in the context environment
    //這個(gè)主要留給子類去實(shí)現(xiàn)
        initPropertySources();

        // Validate that all properties marked as required are resolvable
        // see ConfigurablePropertyResolver#setRequiredProperties
    //校驗(yàn)必須初始化的參數(shù)
        getEnvironment().validateRequiredProperties();

        // Allow for the collection of early ApplicationEvents,
        // to be published once the multicaster is available...
        this.earlyApplicationEvents = new LinkedHashSet<ApplicationEvent>();
    }
  //初始化1些beanFactory參數(shù)
  protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {
        // Tell the internal bean factory to use the context's class loader etc.
    //設(shè)置classLoader
        beanFactory.setBeanClassLoader(getClassLoader());
    //設(shè)置bean表達(dá)式解析器 spring 的el 表達(dá)式
        beanFactory.setBeanExpressionResolver(new StandardBeanExpressionResolver(beanFactory.getBeanClassLoader()));
    //使用資源編輯器來(lái)填充指定的PropertyEditorRegistry。
        beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, getEnvironment()));

        // Configure the bean factory with context callbacks.
    //負(fù)責(zé)注入ResourceLoaderAware, ApplicationEventPublisherAware, MessageSourceAware, ApplicationContextAware ApplicationContext相干特性的Bean
        beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));
        beanFactory.ignoreDependencyInterface(ResourceLoaderAware.class);
        beanFactory.ignoreDependencyInterface(ApplicationEventPublisherAware.class);
        beanFactory.ignoreDependencyInterface(MessageSourceAware.class);
        beanFactory.ignoreDependencyInterface(ApplicationContextAware.class);
        beanFactory.ignoreDependencyInterface(EnvironmentAware.class);

        // BeanFactory interface not registered as resolvable type in a plain factory.
        // MessageSource registered (and found for autowiring) as a bean.
    //This is intended for factory/context references that are supposed to be autowirable but are not defined as beans in the factory: e.g. a dependency of type ApplicationContext resolved to the ApplicationContext instance that the bean is living in.
    //上述英文大概意思就是定義了1個(gè)特殊的bean，但是這個(gè)bean不通過(guò) beanFactory進(jìn)行管理生命周期，beanFactory本身就是1個(gè)bean，本身管理本身就有點(diǎn)奇怪，所以這個(gè)方法是注冊(cè)1些特殊的bean，并且可以進(jìn)行注入
        beanFactory.registerResolvableDependency(BeanFactory.class, beanFactory);
        beanFactory.registerResolvableDependency(ResourceLoader.class, this);
        beanFactory.registerResolvableDependency(ApplicationEventPublisher.class, this);
        beanFactory.registerResolvableDependency(ApplicationContext.class, this);

        // Detect a LoadTimeWeaver and prepare for weaving, if found.
        if (beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) {
            beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));
            // Set a temporary ClassLoader for type matching.
            beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
        }

        // Register default environment beans.
        if (!beanFactory.containsLocalBean(ENVIRONMENT_BEAN_NAME)) {
            beanFactory.registerSingleton(ENVIRONMENT_BEAN_NAME, getEnvironment());
        }
        if (!beanFactory.containsLocalBean(SYSTEM_PROPERTIES_BEAN_NAME)) {
            beanFactory.registerSingleton(SYSTEM_PROPERTIES_BEAN_NAME, getEnvironment().getSystemProperties());
        }
        if (!beanFactory.containsLocalBean(SYSTEM_ENVIRONMENT_BEAN_NAME)) {
            beanFactory.registerSingleton(SYSTEM_ENVIRONMENT_BEAN_NAME, getEnvironment().getSystemEnvironment());
        }
    }

  @Override
    public void refresh() throws BeansException, IllegalStateException {
        synchronized (this.startupShutdownMonitor) {
            // Prepare this context for refreshing.
      //preparecontext之前履行的操作
            prepareRefresh();
      //告知子類刷新bean工廠，spring boot能夠做到改變1個(gè)類進(jìn)行熱部署，我猜可能就調(diào)用了這個(gè)刷新方法去刷新bean工廠，所以改變了1些靜態(tài)變量spring boot是不會(huì)動(dòng)態(tài)刷新的
            // Tell the subclass to refresh the internal bean factory.
            ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();

            // Prepare the bean factory for use in this context.
      //初始化1些bean工廠的參數(shù)
            prepareBeanFactory(beanFactory);

            try {
                // Allows post-processing of the bean factory in context subclasses.
        // 增加處理servletContext的類
                postProcessBeanFactory(beanFactory);

                // Invoke factory processors registered as beans in the context.
                invokeBeanFactoryPostProcessors(beanFactory);

                // Register bean processors that intercept bean creation.
                registerBeanPostProcessors(beanFactory);
        //初始化消息源
                // Initialize message source for this context.
                initMessageSource();
        //初始化消息事件
                // Initialize event multicaster for this context.
                initApplicationEventMulticaster();

                // Initialize other special beans in specific context subclasses.
                onRefresh();

                // Check for listener beans and register them.
                registerListeners();

                // Instantiate all remaining (non-lazy-init) singletons.
                finishBeanFactoryInitialization(beanFactory);
        //發(fā)送refresh事件
                // Last step: publish corresponding event.
                finishRefresh();
            }

            catch (BeansException ex) {
                if (logger.isWarnEnabled()) {
                    logger.warn("Exception encountered during context initialization - " +
                            "cancelling refresh attempt: " + ex);
                }

                // Destroy already created singletons to avoid dangling resources.
                destroyBeans();

                // Reset 'active' flag.
                cancelRefresh(ex);

                // Propagate exception to caller.
                throw ex;
            }

            finally {
                // Reset common introspection caches in Spring's core, since we
                // might not ever need metadata for singleton beans anymore...
                resetCommonCaches();
            }
        }
    }
}

AbstractApplicationContext這個(gè)類比較繁瑣，這里只大概描寫了1下大概的功能，后續(xù)文章會(huì)詳細(xì)進(jìn)行講授，這里主要是講授初始化流程

Spring 整體流程圖

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