tomcat加载web.xml

这几天看tomcat的源码，疑问很多，比如之一“ tomcat 怎么加载 web.xml”，下面是跟踪的过程，其中事件监听器有一个观察者模式，比较好。记录下来以供参考

 >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>tomcat load web.xml>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

    tomcat加载web.xml中用户的servlet到context中去，同时实例化该servlet到/WEB-INF/classes/中
    过程大致如下

    由事件接收器 接收 到CONFIGURE_START_EVENT的消息后，才会触发处理加载web.xml的动作，

            /**
              * The LifecycleEvent type for the "configure_start" event. Used by those
              * components that use a separate component to perform configuration and
              * need to signal when configuration should be performed - usually after
              * {@link #BEFORE_START_EVENT} and before {@link #START_EVENT}.
              */
             public static final String CONFIGURE_START_EVENT = "configure_start";

    那么又是谁来把该消息注册到监听器中的呢？如下，从启动过程中进行查找：

  org.apache.catalina.startup.Bootstrap.start()
   -->org.apache.catalina.startup.Catalina.start()
   ----》load()
   ------》
      getServer().init();
      Server==="org.apache.catalina.core.StandardServer"
      -----》StandardServer.initInternal()
        StandardServer.startInternal()
              ---》
                     void java.org.apache.catalina.util.LifecycleBase.fireLifecycleEvent(String type, Object data)

                             fireLifecycleEvent(CONFIGURE_START_EVENT, null);
                              ---》
                              LifecycleSupport fireLifecycleEvent(CONFIGURE_START_EVENT, null);

                                 由LifecycleSupport 来广播给所有的接收者，
                                  接收者根据需要来判断是否需要处理【此处用到观察者模式 】

                              而public class ContextConfig implements LifecycleListener
                              是所谓的接收者
                              其重写的 lifecycleEvent(LifecycleEvent event)方法中

                               if (event.getType().equals(Lifecycle.CONFIGURE_START_EVENT)) {

                                configureStart();该方法是进行加载的具体方法  

             protected synchronized void configureStart()
                  -----------------》webconfig()
                                                         ：：：：：

                webconfig()中
                            {
                                                     String resource =
                                                             "/WEB-INF/classes/" + binding.getName();
                                                     try {
                                                         URL url = sContext.getResource(resource);
                                                         processAnnotationsUrl(url, webXml,
                                                                 webXml.isMetadataComplete());
                                                     } catch (MalformedURLException e) {
                                                         log.error(sm.getString(
                                                                 "contextConfig.webinfClassesUrl",
                                                                 resource), e);
                                                     }

                            }

    ---------------》
     void java.org.apache.catalina.startup.ContextConfig.processAnnotationsUrl(URL url, WebXml fragment, boolean handlesTypesOnly)
                 ----------》
                  void java.org.apache.catalina.startup.ContextConfig.processAnnotationsJndi(URL url, WebXml fragment, boolean handlesTypesOnly)
                         ------------》
                              void java.org.apache.catalina.startup.ContextConfig.processAnnotationsStream(InputStream is, WebXml fragment, boolean handlesTypesOnly) throws ClassFormatException, IOException
                                     --------------》
                                          void java.org.apache.catalina.startup.ContextConfig.processAnnotationWebServlet(String className, AnnotationEntry ae, WebXml fragment)

                                                  ---------》
                                                   fragment.addServlet(servletDef);
                                                   fragment.addServletMapping(urlPattern, servletName);

     ------->webXml.configureContext(context);

                  public void configureContext(Context context) {
                       Wrapper wrapper = context.createWrapper();
                       context.addChild(wrapper);
                       context.addServletMapping(entry.getKey(), entry.getValue());

   >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>tomcat load web.xml>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>