Servletfilter在AWS上返回“代理错误”

我已经设置了一个Filter来为我的GWT Web应用程序添加爬虫支持。 我们的想法是捕获包含“ _escaped_fragment_= ”的所有请求，并为爬虫提供快照。

我使用Guice设置了Filter ，如下所示：

 filter("/*").through(CrawlerFilter.class); 

以下是CrawlerFilter类的代码（非常感谢Patrick ）：

 @Singleton public class CrawlerFilter implements Filter { private static final Logger logger = Logger.getLogger(CrawlerFilter.class.getName()); /** * Special URL token that gets passed from the crawler to the servlet * filter. This token is used in case there are already existing query * parameters. */ private static final String ESCAPED_FRAGMENT_FORMAT1 = "_escaped_fragment_="; private static final int ESCAPED_FRAGMENT_LENGTH1 = ESCAPED_FRAGMENT_FORMAT1.length(); /** * Special URL token that gets passed from the crawler to the servlet * filter. This token is used in case there are not already existing query * parameters. */ private static final String ESCAPED_FRAGMENT_FORMAT2 = "&" + ESCAPED_FRAGMENT_FORMAT1; private static final int ESCAPED_FRAGMENT_LENGTH2 = ESCAPED_FRAGMENT_FORMAT2.length(); private class SyncAllAjaxController extends NicelyResynchronizingAjaxController { private static final long serialVersionUID = 1L; @Override public boolean processSynchron(HtmlPage page, WebRequest request, boolean async) { return true; } } private WebClient webClient = null; private static final long _pumpEventLoopTimeoutMillis = 30000; private static final long _jsTimeoutMillis = 1000; private static final long _pageWaitMillis = 200; final int _maxLoopChecks = 2; public void doFilter(ServletRequest request, ServletResponse response, FilterChain filterChain) throws IOException, ServletException { // Grab the request uri and query strings. final HttpServletRequest httpRequest = (HttpServletRequest) request; final String requestURI = httpRequest.getRequestURI(); final String queryString = httpRequest.getQueryString(); final HttpServletResponse httpResponse = (HttpServletResponse) response; if ((queryString != null) && (queryString.contains(ESCAPED_FRAGMENT_FORMAT1))) { // This is a Googlebot crawler request, let's return a static // indexable html page post javascript execution, as rendered in the browser. final String domain = httpRequest.getServerName(); final int port = httpRequest.getServerPort(); // Rewrite the URL back to the original #! version // -- basically remove _escaped_fragment_ from the query. // Unescape any %XX characters as need be. final String urlStringWithHashFragment = requestURI + rewriteQueryString(queryString); final String scheme = httpRequest.getScheme(); final URL urlWithHashFragment = new URL(scheme, "127.0.0.1", port, urlStringWithHashFragment); // get from localhost final WebRequest webRequest = new WebRequest(urlWithHashFragment); // Use the headless browser to obtain an HTML snapshot. webClient = new WebClient(BrowserVersion.FIREFOX_3_6); webClient.getCache().clear(); webClient.setJavaScriptEnabled(true); webClient.setThrowExceptionOnScriptError(false); webClient.setRedirectEnabled(false); webClient.setAjaxController(new SyncAllAjaxController()); webClient.setCssErrorHandler(new SilentCssErrorHandler()); if (logger.getLevel() == Level.FINEST) logger.log(Level.FINEST, "HtmlUnit starting webClient.getPage(webRequest) where webRequest = " + webRequest.toString()); final HtmlPage page = webClient.getPage(webRequest); // Important! Give the headless browser enough time to execute // JavaScript // The exact time to wait may depend on your application. webClient.getJavaScriptEngine().pumpEventLoop(_pumpEventLoopTimeoutMillis); int waitForBackgroundJavaScript = webClient.waitForBackgroundJavaScript(_jsTimeoutMillis); int loopCount = 0; while (waitForBackgroundJavaScript > 0 && loopCount < _maxLoopChecks) { ++loopCount; waitForBackgroundJavaScript = webClient.waitForBackgroundJavaScript(_jsTimeoutMillis); if (waitForBackgroundJavaScript == 0) { if (logger.getLevel() == Level.FINEST) logger.log(Level.FINEST, "HtmlUnit exits background javascript at loop counter " + loopCount); break; } synchronized (page) { if (logger.getLevel() == Level.FINEST) logger.log(Level.FINEST, "HtmlUnit waits for background javascript at loop counter " + loopCount); try { page.wait(_pageWaitMillis); } catch (InterruptedException e) { logger.log(Level.SEVERE, "HtmlUnit ERROR on page.wait at loop counter " + loopCount); e.printStackTrace(); } } } webClient.getAjaxController().processSynchron(page, webRequest, false); if (webClient.getJavaScriptEngine().isScriptRunning()) { logger.log(Level.WARNING, "HtmlUnit webClient.getJavaScriptEngine().shutdownJavaScriptExecutor()"); webClient.getJavaScriptEngine().shutdownJavaScriptExecutor(); } // Return the static snapshot. final String staticSnapshotHtml = page.asXml(); httpResponse.setContentType("text/html;charset=UTF-8"); final PrintWriter out = httpResponse.getWriter(); out.println("
"); out.println("
This is a non-interactive snapshot for crawlers. Follow this link for the interactive application.
"); out.println("
"); out.println(staticSnapshotHtml); // Close web client. webClient.closeAllWindows(); out.println(""); out.flush(); out.close(); if (logger.getLevel() == Level.FINEST) logger.log(Level.FINEST, "HtmlUnit completed webClient.getPage(webRequest) where webRequest = " + webRequest.toString()); } else { if (requestURI.contains(".nocache.")) { // Ensure the gwt nocache bootstrapping file is never cached. // References: // https://stackoverflow.com/questions/4274053/how-to-clear-cache-in-gwt // http://seewah.blogspot.com/2009/02/gwt-tips-2-nocachejs-getting-cached-in.html // final Date now = new Date(); httpResponse.setDateHeader("Date", now.getTime()); httpResponse.setDateHeader("Expires", now.getTime() - 86400000L); // One day old. httpResponse.setHeader("Pragma", "no-cache"); httpResponse.setHeader("Cache-control", "no-cache, no-store, must-revalidate"); } filterChain.doFilter(request, response); } } /** * Maps from the query string that contains _escaped_fragment_ to one that * doesn't, but is instead followed by a hash fragment. It also unescapes * any characters that were escaped by the crawler. If the query string does * not contain _escaped_fragment_, it is not modified. * * @param queryString * @return A modified query string followed by a hash fragment if * applicable. The non-modified query string otherwise. * @throws UnsupportedEncodingException */ private static String rewriteQueryString(String queryString) throws UnsupportedEncodingException { // Seek the escaped fragment. int index = queryString.indexOf(ESCAPED_FRAGMENT_FORMAT2); int length = ESCAPED_FRAGMENT_LENGTH2; if (index == -1) { index = queryString.indexOf(ESCAPED_FRAGMENT_FORMAT1); length = ESCAPED_FRAGMENT_LENGTH1; } if (index != -1) { // Found the escaped fragment, so build back the original decoded // one. final StringBuilder queryStringSb = new StringBuilder(); // Add url parameters if any. if (index > 0) { queryStringSb.append("?"); queryStringSb.append(queryString.substring(0, index)); } // Add the hash fragment as a replacement for the escaped fragment. queryStringSb.append("#!"); // Add the decoded token. final String token2Decode = queryString.substring(index + length, queryString.length()); final String tokenDecoded = URLDecoder.decode(token2Decode, "UTF-8"); queryStringSb.append(tokenDecoded); return queryStringSb.toString(); } return queryString; } @Override public void destroy() { if (webClient != null) webClient.closeAllWindows(); } @Override public void init(FilterConfig config) throws ServletException { } } 

它使用HtmlUnit来创建快照。

然而; 当我尝试使用常规浏览器访问快照时发生错误。 我输入的URL是以下forms：

 http://www.myapp.com/?_escaped_fragment_=myobject%3Bid%3D507ac730e4b0e2b7a73b1b81 

但Filter的处理会导致以下错误：

 Proxy Error The proxy server received an invalid response from an upstream server. The proxy server could not handle the request GET /. Reason: Error reading from remote server Apache/2.2.22 (Amazon) Server at www.myapp.com Port 80 

任何帮助，将不胜感激。