Tomcat源码---请求处理三

一,这一章节主要讲request与response通过管道,阀门在各个容器间运行 

1,connector.getContainer().getPipeline().getFirst().invoke(request, response);

这一步是StandardEngine获取StandardPipeline被StandardEngineValve进行过滤后执行到StandardHost

 

 public final void invoke(Request request, Response response)
        throws IOException, ServletException {

        // Select the Host to be used for this Request
        Host host = request.getHost();
        if (host == null) {
            response.sendError
                (HttpServletResponse.SC_BAD_REQUEST,
                 sm.getString("standardEngine.noHost", 
                              request.getServerName()));
            return;
        }

        // Ask this Host to process this request
        //这个是StandardHost通过管道要到下一个容器去
       //Host要经过两个阀门由这里的ErrorReportValve与下一个的StandarHostValve
        host.getPipeline().getFirst().invoke(request, response);

    }

   以下到了ErrorReportValve#invoke

 

 /**
     * Invoke the next Valve in the sequence. When the invoke returns, check
     * the response state, and output an error report is necessary.
     *
     * @param request The servlet request to be processed
     * @param response The servlet response to be created
     *
     * @exception IOException if an input/output error occurs
     * @exception ServletException if a servlet error occurs
     */
    public void invoke(Request request, Response response)
        throws IOException, ServletException {

        // Perform the request
         //StandHostValve阀门的执行
        getNext().invoke(request, response);

        Throwable throwable =
            (Throwable) request.getAttribute(Globals.EXCEPTION_ATTR);

        if (response.isCommitted()) {
            return;
        }

        if (throwable != null) {

            // The response is an error
            response.setError();

            // Reset the response (if possible)
            try {
                response.reset();
            } catch (IllegalStateException e) {
                ;
            }

            response.sendError
                (HttpServletResponse.SC_INTERNAL_SERVER_ERROR);

        }

        response.setSuspended(false);

        try {
            report(request, response, throwable);
        } catch (Throwable tt) {
            ;
        }

    }

  再执行StandardHostValve#invoke

public final void invoke(Request request, Response response)
        throws IOException, ServletException {

        // Select the Context to be used for this Request
        //容器StandardContext
        Context context = request.getContext();
        if (context == null) {
            response.sendError
                (HttpServletResponse.SC_INTERNAL_SERVER_ERROR,
                 sm.getString("standardHost.noContext"));
            return;
        }

        // Bind the context CL to the current thread
        if( context.getLoader() != null ) {
            // Not started - it should check for availability first
            // This should eventually move to Engine, it's generic. 
           //把WebappClassLoader设置进线程
            Thread.currentThread().setContextClassLoader
                    (context.getLoader().getClassLoader());
        }

        // Ask this Context to process this request
       //下一个管道StandardContextValve
        context.getPipeline().getFirst().invoke(request, response);

        // Access a session (if present) to update last accessed time, based on a
        // strict interpretation of the specification
        if (Globals.STRICT_SERVLET_COMPLIANCE) {
            request.getSession(false);
        }

        // Error page processing
       //页面错误进行暂停
        response.setSuspended(false);

        Throwable t = (Throwable) request.getAttribute(Globals.EXCEPTION_ATTR);

        if (t != null) {
            throwable(request, response, t);
        } else {
        //
            status(request, response);
        }

        // Restore the context classloader
        Thread.currentThread().setContextClassLoader
            (StandardHostValve.class.getClassLoader());

    }

 执行到了StandContextValve#invoke

    /**
     * Select the appropriate child Wrapper to process this request,
     * based on the specified request URI.  If no matching Wrapper can
     * be found, return an appropriate HTTP error.
     *
     * @param request Request to be processed
     * @param response Response to be produced
     * @param valveContext Valve context used to forward to the next Valve
     *
     * @exception IOException if an input/output error occurred
     * @exception ServletException if a servlet error occurred
     */
    public final void invoke(Request request, Response response)
        throws IOException, ServletException {

        // Disallow any direct access to resources under WEB-INF or META-INF
        //不允许访问以下两个目录的资源文件
        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;
        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) {
            Thread.currentThread().setContextClassLoader(
                    context.getLoader().getClassLoader());
        }

        // Select the Wrapper to be used for this Request
        //获取StandardWrapper,这个不允许有子容器
        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
        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;
                ServletRequestListener listener =
                    (ServletRequestListener) instances[i];
                try {
                    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;
                }
            }
        }

        //StandardWrapperValve的执行,这下对servlet,filter,listener进行了处理
        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 {
                    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);
                }
            }
        }
                
    }