tomcat源码解析--StandardContextValve

standardContext 的 基础阀 StandardContextValve

主要方法invoke()

// 判断 request 的请求路径是否符合规范
MessageBytes requestPathMB = request.getRequestPathMB();
        if ((requestPathMB.startsWithIgnoreCase("/META-INF/", 0))
            || (requestPathMB.equalsIgnoreCase("/META-INF"))
            || (requestPathMB.startsWithIgnoreCase("/WEB-INF/", 0))
            || (requestPathMB.equalsIgnoreCase("/WEB-INF"))) {
            notFound(response);
            return;
        }

        // Wait if we are reloading
        boolean reloaded = false;
//是否暂停（如果暂停肯定是在reload）
        while (context.getPaused()) {
            reloaded = true;
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                ;
            }
        }

        // Reloading will have stopped the old webappclassloader and
        // created a new one
        if (reloaded &&
                context.getLoader() != null &&
                context.getLoader().getClassLoader() != null) {
//reload时，重新设置一个classloader
            Thread.currentThread().setContextClassLoader(
                    context.getLoader().getClassLoader());
        }

        // Select the Wrapper to be used for this Request
//请求的servlet
        Wrapper wrapper = request.getWrapper();
        if (wrapper == null) {
            notFound(response);
            return;
        } else if (wrapper.isUnavailable()) {
            // May be as a result of a reload, try and find the new wrapper
            wrapper = (Wrapper) container.findChild(wrapper.getName());
            if (wrapper == null) {
                notFound(response);
                return;
            }
        }

        // Normal request processing
//得到所有的监听
        Object instances[] = context.getApplicationEventListeners();

        ServletRequestEvent event = null;

        if ((instances != null) 
                && (instances.length > 0)) {
            event = new ServletRequestEvent
                (((StandardContext) container).getServletContext(), 
                 request.getRequest());
            // create pre-service event
            for (int i = 0; i < instances.length; i++) {
                if (instances[i] == null)
                    continue;
                if (!(instances[i] instanceof ServletRequestListener))
                    continue;
//只处理其中的ServletRequestEvent
                ServletRequestListener listener =
                    (ServletRequestListener) instances[i];
                try {
//触发监听的事件
                  listener.requestInitialized(event);
                } catch (Throwable t) {
                    container.getLogger().error(sm.getString("standardContext.requestListener.requestInit",
                                     instances[i].getClass().getName()), t);
                    ServletRequest sreq = request.getRequest();
                    sreq.setAttribute(Globals.EXCEPTION_ATTR,t);
                    return;
                }
            }
        }
//在context 的基础阀 中 调用pipeline中load的所有wrapper的value
        wrapper.getPipeline().getFirst().invoke(request, response)

        if ((instances !=null ) &&
                (instances.length > 0)) {
            // create post-service event
            for (int i = 0; i < instances.length; i++) {
                if (instances[i] == null)
                    continue;
                if (!(instances[i] instanceof ServletRequestListener))
                    continue;
                ServletRequestListener listener =
                    (ServletRequestListener) instances[i];
                try {
//servlet 调用结束之后，触发的销毁事件
                    listener.requestDestroyed(event);
                } catch (Throwable t) {
                    container.getLogger().error(sm.getString("standardContext.requestListener.requestDestroy",
                                     instances[i].getClass().getName()), t);
                    ServletRequest sreq = request.getRequest();
                    sreq.setAttribute(Globals.EXCEPTION_ATTR,t);
                }
            }
        }