Tomcat请求处理流程

Tomcat+Struts1.x默认的ReqeustProcessor的请求处理流程

Tomcat+Struts+Spring2.5.x提供的DelegatingRequestProcessor的请求处理流程

Struts1.x默认的RequestProcessor得到Action的方法：processActionCreate

processActionCreate(HttpServletRequest request, HttpServletResponse response, ActionMapping mapping)：

    /**     * <p>Return an <code>Action</code> instance that will be used to process     * the current request, creating a new one if necessary.</p>     *     * @param request  The servlet request we are processing     * @param response The servlet response we are creating     * @param mapping  The mapping we are using     * @return An <code>Action</code> instance that will be used to process     *         the current request.     * @throws IOException if an input/output error occurs     */    protected Action processActionCreate(HttpServletRequest request,        HttpServletResponse response, ActionMapping mapping)        throws IOException {        // Acquire the Action instance we will be using (if there is one)        String className = mapping.getType();        if (log.isDebugEnabled()) {            log.debug(" Looking for Action instance for class " + className);        }        // If there were a mapping property indicating whether        // an Action were a singleton or not ([true]),        // could we just instantiate and return a new instance here?        Action instance;        synchronized (actions) {            // Return any existing Action instance of this class            instance = (Action) actions.get(className);            if (instance != null) {                if (log.isTraceEnabled()) {                    log.trace("  Returning existing Action instance");                }                return (instance);            }            // Create and return a new Action instance            if (log.isTraceEnabled()) {                log.trace("  Creating new Action instance");            }            try {                instance = (Action) RequestUtils.applicationInstance(className);                // Maybe we should propagate this exception                // instead of returning null.            } catch (Exception e) {                log.error(getInternal().getMessage("actionCreate",                        mapping.getPath()), e);                response.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR,                    getInternal().getMessage("actionCreate", mapping.getPath()));                return (null);            }            actions.put(className, instance);        }        if (instance.getServlet() == null) {            instance.setServlet(this.servlet);        }        return (instance);    }

Spring的DelegatingRequestProcessor得到Action的方法：

processActionCreate(HttpServletRequest request, HttpServletResponse response, ActionMapping mapping)：

/** * Override the base class method to return the delegate action. * @see #getDelegateAction */protected Action processActionCreate(HttpServletRequest request, HttpServletResponse response, ActionMapping mapping)throws IOException {                //先试图从Sping的Action容器中获取对应的Action，如果没有找到，再调用Strut提供的RequestProcessor的processActionCreate方法得到对应的Action。Action action = getDelegateAction(mapping);if (action != null) {return action;}//如果没有找到，再调用Strut提供的RequestProcessor的processActionCreate方法得到对应的Action。return super.processActionCreate(request, response, mapping);}

/** * Return the delegate <code>Action</code> for the given mapping. * <p>The default implementation determines a bean name from the * given <code>ActionMapping</code> and looks up the corresponding * bean in the <code>WebApplicationContext</code>. * @param mapping the Struts <code>ActionMapping</code> * @return the delegate <code>Action</code>, or <code>null</code> if none found * @throws BeansException if thrown by <code>WebApplicationContext</code> methods * @see #determineActionBeanName */protected Action getDelegateAction(ActionMapping mapping) throws BeansException {String beanName = determineActionBeanName(mapping);if (!getWebApplicationContext().containsBean(beanName)) {return null;}return (Action) getWebApplicationContext().getBean(beanName, Action.class);}