<!DOCTYPE web-app PUBLIC
 "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
 "http://java.sun.com/dtd/web-app_2_3.dtd" >

<web-app>
 <context-param>
  <param-name>contextConfigLocation</param-name>
  <param-value>
   <!--加載spring配置-->
   classpath:spring.xml
  </param-value>
 </context-param>
 <context-param>
  <param-name>webAppRootKey</param-name>
  <param-value>ServicePlatform.root</param-value>
 </context-param>

 <listener>
  <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
  <!--<listener-class>org.springframework.web.context.request.RequestContextListener</listener-class>-->
 </listener>

 <servlet>
  <servlet-name>spring-dispatcher</servlet-name>
  <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
  <init-param>
   <!--springmvc的配置文件-->
   <param-name>contextConfigLocation</param-name>
   <param-value>classpath:spring-dispatcher.xml</param-value>
  </init-param>
  <load-on-startup>0</load-on-startup>
 </servlet>
 <servlet-mapping>
  <servlet-name>spring-dispatcher</servlet-name>
  <url-pattern>/</url-pattern>
 </servlet-mapping>
</web-app>

 

public interface ServletContainerInitializer {
  void onStartup(Set<Class<?>> var1, ServletContext var2) throws ServletException;
}

@HandlesTypes(LoadServlet.class)
public class MyServletContainerInitializer implements ServletContainerInitializer {
  @Override
  public void onStartup(Set<Class<?>> set, ServletContext servletContext) throws ServletException {
    Iterator var4;
    if (set != null) {
      var4 = set.iterator();
      while (var4.hasNext()) {
        Class<?> clazz = (Class<?>) var4.next();
        if (!clazz.isInterface() && !Modifier.isAbstract(clazz.getModifiers()) && LoadServlet.class.isAssignableFrom(clazz)) {
          try {
            ((LoadServlet) clazz.newInstance()).loadOnstarp(servletContext);
          } catch (Exception e) {
            e.printStackTrace();
          }
        }
      }
    }
  }
}

public interface LoadServlet {

  void loadOnstarp(ServletContext servletContext);
}

public class LoadServletImpl implements LoadServlet {
  @Override
  public void loadOnstarp(ServletContext servletContext) {
    ServletRegistration.Dynamic initServlet = servletContext.addServlet("initServlet", "org.springframework.web.servlet.DispatcherServlet");
    initServlet.setLoadOnStartup(1);
    initServlet.addMapping("/init");
 }
}

@HandlesTypes(WebApplicationInitializer.class)
public class SpringServletContainerInitializer implements ServletContainerInitializer {
 @Override
 public void onStartup(@Nullable Set<Class<?>> webAppInitializerClasses, ServletContext servletContext)
  throws ServletException {

 List<WebApplicationInitializer> initializers = new LinkedList<>();

 if (webAppInitializerClasses != null) {
  for (Class<?> waiClass : webAppInitializerClasses) {
  // Be defensive: Some servlet containers provide us with invalid classes,
  // no matter what @HandlesTypes says...
  if (!waiClass.isInterface() && !Modifier.isAbstract(waiClass.getModifiers()) &&
   WebApplicationInitializer.class.isAssignableFrom(waiClass)) {
   try {
   initializers.add((WebApplicationInitializer)
    ReflectionUtils.accessibleConstructor(waiClass).newInstance());
   }
   catch (Throwable ex) {
   throw new ServletException("Failed to instantiate WebApplicationInitializer class", ex);
   }
  }
  }
 }

 if (initializers.isEmpty()) {
  servletContext.log("No Spring WebApplicationInitializer types detected on classpath");
  return;
 }

 servletContext.log(initializers.size() + " Spring WebApplicationInitializers detected on classpath");
 AnnotationAwareOrderComparator.sort(initializers);
 for (WebApplicationInitializer initializer : initializers) {
  initializer.onStartup(servletContext);
 }
 }

}

  //父容器
  @Override
  protected Class<?>[] getRootConfigClasses() {
    return new Class<?>[]{SpringContainer.class};
  }

  //SpringMVC配置子容器
  @Override
  protected Class<?>[] getServletConfigClasses() {
    return new Class<?>[]{MvcContainer.class};
  }

  //獲取DispatcherServlet的映射信息
  @Override
  protected String[] getServletMappings() {
    return new String[]{"/"};
  }

 // filter配置
  @Override
  protected Filter[] getServletFilters() {
    MyFilter myFilter = new MyFilter();
    CorsFilter corsFilter = new CorsFilter();
    return new Filter[]{myFilter,corsFilter};
  }

@ComponentScan(value = "com.dark",excludeFilters = {
    @ComponentScan.Filter(type = FilterType.ANNOTATION,classes = {Controller.class})
})
public class SpringContainer {
}

@ComponentScan(value = "com.dark",includeFilters = {
    @ComponentScan.Filter(type = FilterType.ANNOTATION,classes = {Controller.class})
},useDefaultFilters = false)
public class MvcContainer {
}

 public void onStartup(ServletContext servletContext) throws ServletException {
 super.onStartup(servletContext);
 //注冊DispatcherServlet
 registerDispatcherServlet(servletContext);
 }

 public void onStartup(ServletContext servletContext) throws ServletException {
 registerContextLoaderListener(servletContext);
 }

 protected void registerContextLoaderListener(ServletContext servletContext) {

 //創(chuàng)建spring上下文，注冊了SpringContainer
 WebApplicationContext rootAppContext = createRootApplicationContext();
 if (rootAppContext != null) {
  //創(chuàng)建監(jiān)聽器
  ContextLoaderListener listener = new ContextLoaderListener(rootAppContext);
  listener.setContextInitializers(getRootApplicationContextInitializers());
  servletContext.addListener(listener);
 }
 }

 protected WebApplicationContext createRootApplicationContext() {
 Class<?>[] configClasses = getRootConfigClasses();
 if (!ObjectUtils.isEmpty(configClasses)) {
  AnnotationConfigWebApplicationContext context = new AnnotationConfigWebApplicationContext();
  context.register(configClasses);
  return context;
 }
 else {
  return null;
 }
 }

 public void contextInitialized(ServletContextEvent event) {
 initWebApplicationContext(event.getServletContext());
 }

 */
 public WebApplicationContext initWebApplicationContext(ServletContext servletContext) {
 long startTime = System.currentTimeMillis();
 try {
  // Store context in local instance variable, to guarantee that
  // it is available on ServletContext shutdown.
  if (this.context == null) {
  this.context = createWebApplicationContext(servletContext);
  }
  if (this.context instanceof ConfigurableWebApplicationContext) {
  ConfigurableWebApplicationContext cwac = (ConfigurableWebApplicationContext) this.context;
  if (!cwac.isActive()) {
   // The context has not yet been refreshed -> provide services such as
   // setting the parent context, setting the application context id, etc
   if (cwac.getParent() == null) {
   // The context instance was injected without an explicit parent ->
   // determine parent for root web application context, if any.
   ApplicationContext parent = loadParentContext(servletContext);
   cwac.setParent(parent);
   }
   configureAndRefreshWebApplicationContext(cwac, servletContext);
  }
  }
  servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, this.context);

  ClassLoader ccl = Thread.currentThread().getContextClassLoader();
  if (ccl == ContextLoader.class.getClassLoader()) {
  currentContext = this.context;
  }
  else if (ccl != null) {
  currentContextPerThread.put(ccl, this.context);
  }

  return this.context;
 }
 }

 protected void registerDispatcherServlet(ServletContext servletContext) {
 String servletName = getServletName();
 Assert.hasLength(servletName, "getServletName() must not return null or empty");

 //創(chuàng)建springmvc的上下文，注冊了MvcContainer類
 WebApplicationContext servletAppContext = createServletApplicationContext();
 Assert.notNull(servletAppContext, "createServletApplicationContext() must not return null");

 //創(chuàng)建DispatcherServlet
 FrameworkServlet dispatcherServlet = createDispatcherServlet(servletAppContext);
 Assert.notNull(dispatcherServlet, "createDispatcherServlet(WebApplicationContext) must not return null");
 dispatcherServlet.setContextInitializers(getServletApplicationContextInitializers());

 ServletRegistration.Dynamic registration = servletContext.addServlet(servletName, dispatcherServlet);
 if (registration == null) {
  throw new IllegalStateException("Failed to register servlet with name '" + servletName + "'. " +
   "Check if there is another servlet registered under the same name.");
 }

 /*
 * 如果該元素的值為負數或者沒有設置，則容器會當Servlet被請求時再加載。
  如果值為正整數或者0時，表示容器在應用啟動時就加載并初始化這個servlet，
  值越小，servlet的優(yōu)先級越高，就越先被加載
 * */
 registration.setLoadOnStartup(1);
 registration.addMapping(getServletMappings());
 registration.setAsyncSupported(isAsyncSupported());

 Filter[] filters = getServletFilters();
 if (!ObjectUtils.isEmpty(filters)) {
  for (Filter filter : filters) {
  registerServletFilter(servletContext, filter);
  }
 }

 customizeRegistration(registration);
 }

 protected WebApplicationContext createServletApplicationContext() {
 AnnotationConfigWebApplicationContext context = new AnnotationConfigWebApplicationContext();
 Class<?>[] configClasses = getServletConfigClasses();
 if (!ObjectUtils.isEmpty(configClasses)) {
  context.register(configClasses);
 }
 return context;
 }

 public final void init() throws ServletException {
 ...省略
 
 // Let subclasses do whatever initialization they like.
 initServletBean();
 }

 protected final void initServletBean() throws ServletException {
 try {
  this.webApplicationContext = initWebApplicationContext();
  initFrameworkServlet();
 }
 }

 protected WebApplicationContext initWebApplicationContext() {
 //這里會從servletContext中獲取到父容器，就是通過監(jiān)聽器加載的容器
 WebApplicationContext rootContext =
  WebApplicationContextUtils.getWebApplicationContext(getServletContext());
 WebApplicationContext wac = null;

 if (this.webApplicationContext != null) {
  // A context instance was injected at construction time -> use it
  wac = this.webApplicationContext;
  if (wac instanceof ConfigurableWebApplicationContext) {
  ConfigurableWebApplicationContext cwac = (ConfigurableWebApplicationContext) wac;
  if (!cwac.isActive()) {
   if (cwac.getParent() == null) {
   cwac.setParent(rootContext);
   }
   //容器加載
   configureAndRefreshWebApplicationContext(cwac);
  }
  }
 }
 if (wac == null) {
  wac = findWebApplicationContext();
 }
 if (wac == null) {
  wac = createWebApplicationContext(rootContext);
 }

 if (!this.refreshEventReceived) {
  synchronized (this.onRefreshMonitor) {
  onRefresh(wac);
  }
 }

 if (this.publishContext) {
  // Publish the context as a servlet context attribute.
  String attrName = getServletContextAttributeName();
  getServletContext().setAttribute(attrName, wac);
 }

 return wac;
 }