tomcat解析(十五)StandardContext.start的其它内容

在StandardContext的start()方法里,除了触发相应的LifecycleEvent之外,当然还有其它的处理,下面我们来一一看看其中一些需要了解的内容;
1.如果设置了支持JNDI,下面这段代码将为此CONTEXT注册一个监听器
if (ok && isUseNaming()) { if (namingContextListener == null) { namingContextListener = new NamingContextListener(); namingContextListener.setName(getNamingContextName()); addLifecycleListener(namingContextListener); } }

2.在触发START_EVENT之前,调用本身持有的logger,cluster,realm,resources,children,pipeline的start方法启动子对象,触发START_EVENT,此事件所做的工作在上两篇已进行了初步讲解:
3.如果是集群方式的,还需要实例化一个clustered manager
4.如果是支持注释的,那还要产生一个用于处理注释的处理器
 if (ok && !getIgnoreAnnotations()) { if (annotationProcessor == null) { if (isUseNaming() && namingContextListener != null) { annotationProcessor = new DefaultAnnotationProcessor(namingContextListener.getEnvContext()); } else { annotationProcessor = new DefaultAnnotationProcessor(null); } } getServletContext().setAttribute (AnnotationProcessor.class.getName(), annotationProcessor); }

5.启动已有的listener
 // Configure and call application event listeners if (ok) { if (!listenerStart()) { log.error( "Error listenerStart"); ok = false; } } 

 listenerStart方法如下:
 /** * Configure the set of instantiated application event listeners * for this Context. Return <code>true</code> if all listeners wre * initialized successfully, or <code>false</code> otherwise. */ public boolean listenerStart() { if (log.isDebugEnabled()) log.debug("Configuring application event listeners"); // Instantiate the required listeners ClassLoader loader = getLoader().getClassLoader(); String listeners[] = findApplicationListeners(); //先找到在web.xml里配置的<linstener> Object results[] = new Object[listeners.length]; boolean ok = true; for (int i = 0; i < results.length; i++) { if (getLogger().isDebugEnabled()) getLogger().debug(" Configuring event listener class '" + listeners[i] + "'"); try { Class clazz = loader.loadClass(listeners[i]); results[i] = clazz.newInstance(); //实例化这些监听器 // Annotation processing if (!getIgnoreAnnotations()) { getAnnotationProcessor().processAnnotations(results[i]); //处理注释处构造 getAnnotationProcessor().postConstruct(results[i]); } } catch (Throwable t) { getLogger().error (sm.getString("standardContext.applicationListener", listeners[i]), t); ok = false; } } if (!ok) { getLogger().error(sm.getString("standardContext.applicationSkipped")); return (false); } // Sort listeners in two arrays ArrayList eventListeners = new ArrayList(); ArrayList lifecycleListeners = new ArrayList(); for (int i = 0; i < results.length; i++) { //对具体监听器类型进行分类 if ((results[i] instanceof ServletContextAttributeListener) || (results[i] instanceof ServletRequestAttributeListener) || (results[i] instanceof ServletRequestListener) || (results[i] instanceof HttpSessionAttributeListener)) { eventListeners.add(results[i]); } if ((results[i] instanceof ServletContextListener) || (results[i] instanceof HttpSessionListener)) { lifecycleListeners.add(results[i]); } } setApplicationEventListeners(eventListeners.toArray()); //放入到Context对应的监听器List setApplicationLifecycleListeners(lifecycleListeners.toArray()); // Send application start events if (getLogger().isDebugEnabled()) getLogger().debug("Sending application start events"); Object instances[] = getApplicationLifecycleListeners(); if (instances == null) return (ok); ServletContextEvent event = new ServletContextEvent(getServletContext()); //产生一个容器初始化事件 for (int i = 0; i < instances.length; i++) { if (instances[i] == null) continue; if (!(instances[i] instanceof ServletContextListener)) continue; ServletContextListener listener = (ServletContextListener) instances[i]; try { fireContainerEvent("beforeContextInitialized", listener); listener.contextInitialized(event); //触发监听器事件 fireContainerEvent("afterContextInitialized", listener); } catch (Throwable t) { fireContainerEvent("afterContextInitialized", listener); getLogger().error (sm.getString("standardContext.listenerStart", instances[i].getClass().getName()), t); ok = false; } } return (ok); }

6.启动实例化Servlet
   if (ok) { loadOnStartup(findChildren()); } /** * Load and initialize all servlets marked "load on startup" in the * web application deployment descriptor. * * @param children Array of wrappers for all currently defined * servlets (including those not declared load on startup) */ public void loadOnStartup(Container children[]) { // Collect "load on startup" servlets that need to be initialized TreeMap map = new TreeMap(); for (int i = 0; i < children.length; i++) { Wrapper wrapper = (Wrapper) children[i]; int loadOnStartup = wrapper.getLoadOnStartup(); if (loadOnStartup < 0) continue; Integer key = Integer.valueOf(loadOnStartup); ArrayList list = (ArrayList) map.get(key); if (list == null) { list = new ArrayList(); map.put(key, list); } list.add(wrapper); } // Load the collected "load on startup" servlets Iterator keys = map.keySet().iterator(); while (keys.hasNext()) { Integer key = (Integer) keys.next(); ArrayList list = (ArrayList) map.get(key); Iterator wrappers = list.iterator(); while (wrappers.hasNext()) { Wrapper wrapper = (Wrapper) wrappers.next(); try { wrapper.load(); //调用StandardWrapper.load() } catch (ServletException e) { getLogger().error(sm.getString("standardWrapper.loadException", getName()), StandardWrapper.getRootCause(e)); // NOTE: load errors (including a servlet that throws // UnavailableException from tht init() method) are NOT // fatal to application startup } } } } 

    StandardWrapper.load方法如下:
    /** * Load and initialize an instance of this servlet, if there is not already * at least one initialized instance. This can be used, for example, to * load servlets that are marked in the deployment descriptor to be loaded * at server startup time. * <p> * <b>IMPLEMENTATION NOTE</b>: Servlets whose classnames begin with * <code>org.apache.catalina.</code> (so-called "container" servlets) * are loaded by the same classloader that loaded this class, rather than * the classloader for the current web application. * This gives such classes access to Catalina internals, which are * prevented for classes loaded for web applications. * * @exception ServletException if the servlet init() method threw * an exception * @exception ServletException if some other loading problem occurs */ public synchronized void load() throws ServletException { instance = loadServlet(); }     
    具体请看其loadServlet源代码,主要是实例化具体的servlet类并调用其init进行初始化,如果loadOnStartup>0且不是JSP的话,还要先模拟一次请求来调用该servlet的service方法