Catalina主要包括Connector和Container，StandardContext就是一个Container，它主要负责对进入的用户请求进行处理。实际来说，不是由它来进行处理，而是交给内部的valve处理。 一个context表示了一个外部应用，它包含多个wrapper，每个wrapper表示一个servlet定义。
/** * Standard implementation of the <b>Context</b> interface. Each * child container must be a Wrapper implementation to process the * requests directed to a particular servlet. * * @author Craig R. McClanahan * @author Remy Maucherat * @version $Revision: 1.112 $ $Date: 2002/09/09 14:39:37 $ */ public class StandardContext extends ContainerBase implements Context { // ----------------------------------------------------------- Constructors /** * Create a new StandardContext component with the default basic Valve. */ public StandardContext() { super(); pipeline.setBasic(new StandardContextValve()); namingResources.setContainer(this); }项目启动时，启动Connector和Context，让各种功能就绪。
/** * Start this Context component. * * @exception LifecycleException if a startup error occurs */ public synchronized void start() throws LifecycleException { if (started) throw new LifecycleException (sm.getString("containerBase.alreadyStarted", logName())); if (debug >= 1) log("Starting"); // Notify our interested LifecycleListeners lifecycle.fireLifecycleEvent(BEFORE_START_EVENT, null); if (debug >= 1) log("Processing start(), current available=" + getAvailable()); setAvailable(false); setConfigured(false); boolean ok = true; // Add missing components as necessary if (getResources() == null) { // (1) Required by Loader if (debug >= 1) log("Configuring default Resources"); try { if ((docBase != null) && (docBase.endsWith(".war"))) setResources(new WARDirContext()); else setResources(new FileDirContext()); } catch (IllegalArgumentException e) { log("Error initializing resources: " + e.getMessage()); ok = false; } } if (ok && (resources instanceof ProxyDirContext)) { DirContext dirContext = ((ProxyDirContext) resources).getDirContext(); if ((dirContext != null) && (dirContext instanceof BaseDirContext)) { ((BaseDirContext) dirContext).setDocBase(getBasePath()); ((BaseDirContext) dirContext).allocate(); } } //类加载器 if (getLoader() == null) { // (2) Required by Manager if (getPrivileged()) { if (debug >= 1) log("Configuring privileged default Loader"); setLoader(new WebappLoader(this.getClass().getClassLoader())); } else { if (debug >= 1) log("Configuring non-privileged default Loader"); setLoader(new WebappLoader(getParentClassLoader())); } } //manager管理session if (getManager() == null) { // (3) After prerequisites if (debug >= 1) log("Configuring default Manager"); setManager(new StandardManager()); } // Initialize character set mapper getCharsetMapper(); // Post work directory postWorkDirectory(); // Reading the "catalina.useNaming" environment variable String useNamingProperty = System.getProperty("catalina.useNaming"); if ((useNamingProperty != null) && (useNamingProperty.equals("false"))) { useNaming = false; } if (ok && isUseNaming()) { if (namingContextListener == null) { namingContextListener = new NamingContextListener(); namingContextListener.setDebug(getDebug()); namingContextListener.setName(getNamingContextName()); addLifecycleListener(namingContextListener); } } // Binding thread 这个功能是什么呢？ ClassLoader oldCCL = bindThread(); // Standard container startup if (debug >= 1) log("Processing standard container startup"); if (ok) { try { addDefaultMapper(this.mapperClass); started = true; // Start our subordinate components, if any //启动loader和logger if ((loader != null) && (loader instanceof Lifecycle)) ((Lifecycle) loader).start(); if ((logger != null) && (logger instanceof Lifecycle)) ((Lifecycle) logger).start(); // Unbinding thread unbindThread(oldCCL); // Binding thread oldCCL = bindThread(); if ((cluster != null) && (cluster instanceof Lifecycle)) ((Lifecycle) cluster).start(); //启动realm if ((realm != null) && (realm instanceof Lifecycle)) ((Lifecycle) realm).start(); if ((resources != null) && (resources instanceof Lifecycle)) ((Lifecycle) resources).start(); // Start our Mappers, if any Mapper mappers[] = findMappers(); for (int i = 0; i < mappers.length; i++) { if (mappers[i] instanceof Lifecycle) ((Lifecycle) mappers[i]).start(); } // Start our child containers, if any 一般指wrapper Container children[] = findChildren(); for (int i = 0; i < children.length; i++) { if (children[i] instanceof Lifecycle) ((Lifecycle) children[i]).start(); } // Start the Valves in our pipeline (including the basic), // if any if (pipeline instanceof Lifecycle) ((Lifecycle) pipeline).start(); // Notify our interested LifecycleListeners lifecycle.fireLifecycleEvent(START_EVENT, null); if ((manager != null) && (manager instanceof Lifecycle)) ((Lifecycle) manager).start(); } finally { // Unbinding thread unbindThread(oldCCL); } } if (!getConfigured()) ok = false; // We put the resources into the servlet context if (ok) getServletContext().setAttribute (Globals.RESOURCES_ATTR, getResources()); // Binding thread oldCCL = bindThread(); // Create context attributes that will be required if (ok) { if (debug >= 1) log("Posting standard context attributes"); postWelcomeFiles(); } // Configure and call application event listeners and filters if (ok) { if (!listenerStart()) ok = false; } if (ok) { if (!filterStart()) ok = false; } // Load and initialize all "load on startup" servlets if (ok) loadOnStartup(findChildren()); // Unbinding thread unbindThread(oldCCL); // Set available status depending upon startup success if (ok) { if (debug >= 1) log("Starting completed"); setAvailable(true); } else { log(sm.getString("standardContext.startFailed")); try { stop(); } catch (Throwable t) { log(sm.getString("standardContext.startCleanup"), t); } setAvailable(false); } // Notify our interested LifecycleListeners lifecycle.fireLifecycleEvent(AFTER_START_EVENT, null); } /** * ******************* 这个是干啥的捏？？？？？？************************ * Bind current thread, both for CL purposes and for JNDI ENC support * during : startup, shutdown and realoading of the context. * * @return the previous context class loader */ private ClassLoader bindThread() { ClassLoader oldContextClassLoader = Thread.currentThread().getContextClassLoader(); if (getResources() == null) return oldContextClassLoader; Thread.currentThread().setContextClassLoader (getLoader().getClassLoader()); DirContextURLStreamHandler.bind(getResources()); if (isUseNaming()) { try { ContextBindings.bindThread(this, this); } catch (NamingException e) { // Silent catch, as this is a normal case during the early // startup stages } } return oldContextClassLoader; }请求进入后，Connector调用context的invoke方法。invoke将请求交给其pipeline去处理，由pipeline中的所有valve顺序处理请求。
/** * Process the specified Request, and generate the corresponding Response, * according to the design of this particular Container. * * @param request Request to be processed * @param response Response to be produced * * @exception IOException if an input/output error occurred while * processing * @exception ServletException if a ServletException was thrown * while processing this request */ public void invoke(Request request, Response response) throws IOException, ServletException { // Wait if we are reloading while (getPaused()) { try { Thread.sleep(1000); } catch (InterruptedException e) { ; } } // Normal request processing if (swallowOutput) { try { SystemLogHandler.startCapture(); super.invoke(request, response); } finally { String log = SystemLogHandler.stopCapture(); if (log != null && log.length() > 0) { log(log); } } } else { super.invoke(request, response); } }StandardContext是比较复杂的一块，像一个大容器，包括了类加载器、session管理、wrapper管理等模块，在启动时顺序启动这些模块。在请求进入时，由这些模块互相合作处理请求。所以start()是比较复杂的，这一块我花了好多时间看，还是不特别理解，只是知道了大致的流程。
