filterdispatcher.java

FilterDispatcher源码,些源码是struts2的核心源码.

     * retrieve the servlet context from other sources.
     *
     * @return the servlet context.
     */
    protected ServletContext getServletContext() {
        return filterConfig.getServletContext();
    }

    /**
     * Expose the FilterConfig instance.
     *
     * @return Our FilterConfit instance
     */
    protected FilterConfig getFilterConfig() {
        return filterConfig;
    }

    /**
     * Wrap and return the given request, if needed, so as to to transparently
     * handle multipart data as a wrapped class around the given request.
     *
     * @param request Our ServletRequest object
     * @param response Our ServerResponse object
     * @return Wrapped HttpServletRequest object
     * @throws ServletException on any error
     */
    protected HttpServletRequest prepareDispatcherAndWrapRequest(HttpServletRequest request, HttpServletResponse response) throws ServletException {

        Dispatcher du = Dispatcher.getInstance();

        // Prepare and wrap the request if the cleanup filter hasn't already, cleanup filter should be
        // configured first before struts2 dispatcher filter, hence when its cleanup filter's turn,
        // static instance of Dispatcher should be null.
        if (du == null) {

            Dispatcher.setInstance(dispatcher);

            // prepare the request no matter what - this ensures that the proper character encoding
            // is used before invoking the mapper (see WW-9127)
            dispatcher.prepare(request, response);
        } else {
            dispatcher = du;
        }
        
        try {
            // Wrap request first, just in case it is multipart/form-data
            // parameters might not be accessible through before encoding (ww-1278)
            request = dispatcher.wrapRequest(request, getServletContext());
        } catch (IOException e) {
            String message = "Could not wrap servlet request with MultipartRequestWrapper!";
            LOG.error(message, e);
            throw new ServletException(message, e);
        }

        return request;
    }

    /**
     * Create a string array from a comma-delimited list of packages.
     *
     * @param packages A comma-delimited String listing packages
     * @return A string array of packages
     */
    protected String[] parse(String packages) {
        if (packages == null) {
            return null;
        }
        List<String> pathPrefixes = new ArrayList<String>();

        StringTokenizer st = new StringTokenizer(packages, ", \n\t");
        while (st.hasMoreTokens()) {
            String pathPrefix = st.nextToken().replace('.', '/');
            if (!pathPrefix.endsWith("/")) {
                pathPrefix += "/";
            }
            pathPrefixes.add(pathPrefix);
        }

        return pathPrefixes.toArray(new String[pathPrefixes.size()]);
    }


    /**
     * Process an action or handle a request a static resource.
     * <p/>
     * The filter tries to match the request to an action mapping.
     * If mapping is found, the action processes is delegated to the dispatcher's serviceAction method.
     * If action processing fails, doFilter will try to create an error page via the dispatcher.
     * <p/>
     * Otherwise, if the request is for a static resource,
     * the resource is copied directly to the response, with the appropriate caching headers set.
     * <p/>
     * If the request does not match an action mapping, or a static resource page, 
     * then it passes through.
     *
     * @see javax.servlet.Filter#doFilter(javax.servlet.ServletRequest, javax.servlet.ServletResponse, javax.servlet.FilterChain)
     */
    public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException {


        HttpServletRequest request = (HttpServletRequest) req;
        HttpServletResponse response = (HttpServletResponse) res;
        ServletContext servletContext = getServletContext();

        String timerKey = "FilterDispatcher_doFilter: ";
        try {
            UtilTimerStack.push(timerKey);
            request = prepareDispatcherAndWrapRequest(request, response);
            ActionMapping mapping;
            try {
                mapping = actionMapper.getMapping(request, dispatcher.getConfigurationManager());
            } catch (Exception ex) {
                LOG.error("error getting ActionMapping", ex);
                dispatcher.sendError(request, response, servletContext, HttpServletResponse.SC_INTERNAL_SERVER_ERROR, ex);
                return;
            }

            if (mapping == null) {
                // there is no action in this request, should we look for a static resource?
                String resourcePath = RequestUtils.getServletPath(request);

                if ("".equals(resourcePath) && null != request.getPathInfo()) {
                    resourcePath = request.getPathInfo();
                }

                if (serveStatic && resourcePath.startsWith("/struts")) {
                    String name = resourcePath.substring("/struts".length());
                    findStaticResource(name, request, response);
                } else {
                    // this is a normal request, let it pass through
                    chain.doFilter(request, response);
                }
                // The framework did its job here
                return;
            }

            dispatcher.serviceAction(request, response, servletContext, mapping);

        } finally {
            try {
                ActionContextCleanUp.cleanUp(req);
            } finally {
                UtilTimerStack.pop(timerKey);
            }
        }
    }

    /**
     * Locate a static resource and copy directly to the response,
     * setting the appropriate caching headers. 
     *
     * @param name The resource name
     * @param request The request
     * @param response The response
     * @throws IOException If anything goes wrong
     */
    protected void findStaticResource(String name, HttpServletRequest request, HttpServletResponse response) throws IOException {
        if (!name.endsWith(".class")) {
            for (String pathPrefix : pathPrefixes) {
                InputStream is = findInputStream(name, pathPrefix);
                if (is != null) {
                    Calendar cal = Calendar.getInstance();
                    
                    // check for if-modified-since, prior to any other headers
                    long ifModifiedSince = 0;
                    try {
                    	ifModifiedSince = request.getDateHeader("If-Modified-Since");
                    } catch (Exception e) {
                    	LOG.warn("Invalid If-Modified-Since header value: '" + request.getHeader("If-Modified-Since") + "', ignoring");
                    }
    				long lastModifiedMillis = lastModifiedCal.getTimeInMillis();
    				long now = cal.getTimeInMillis();
                    cal.add(Calendar.DAY_OF_MONTH, 1);
                    long expires = cal.getTimeInMillis();
                    
    				if (ifModifiedSince > 0 && ifModifiedSince <= lastModifiedMillis) {
    					// not modified, content is not sent - only basic headers and status SC_NOT_MODIFIED
                        response.setDateHeader("Expires", expires);
    					response.setStatus(HttpServletResponse.SC_NOT_MODIFIED);
    					is.close();
    					return;
    				}
                	
                	// set the content-type header
                    String contentType = getContentType(name);
                    if (contentType != null) {
                        response.setContentType(contentType);
                    }

                    if (serveStaticBrowserCache) {
                    	// set heading information for caching static content
                        response.setDateHeader("Date", now);
                        response.setDateHeader("Expires", expires);
                        response.setDateHeader("Retry-After", expires);
                        response.setHeader("Cache-Control", "public");
                        response.setDateHeader("Last-Modified", lastModifiedMillis);
                    } else {
                        response.setHeader("Cache-Control", "no-cache");
                        response.setHeader("Pragma", "no-cache");
                        response.setHeader("Expires", "-1");
                    }

                    try {
                        copy(is, response.getOutputStream());
                    } finally {
                        is.close();
                    }
                    return;
                }
            }
        }

        response.sendError(HttpServletResponse.SC_NOT_FOUND);
    }

    /**
     * Determine the content type for the resource name.
     *
     * @param name The resource name
     * @return The mime type
     */
    protected String getContentType(String name) {
        // NOT using the code provided activation.jar to avoid adding yet another dependency
        // this is generally OK, since these are the main files we server up
        if (name.endsWith(".js")) {
            return "text/javascript";
        } else if (name.endsWith(".css")) {
            return "text/css";
        } else if (name.endsWith(".html")) {
            return "text/html";
        } else if (name.endsWith(".txt")) {
            return "text/plain";
        } else if (name.endsWith(".gif")) {
            return "image/gif";
        } else if (name.endsWith(".jpg") || name.endsWith(".jpeg")) {
            return "image/jpeg";
        } else if (name.endsWith(".png")) {
            return "image/png";
        } else {
            return null;
        }
    }

    /**
     * Copy bytes from the input stream to the output stream.
     *
     * @param input The input stream
     * @param output The output stream
     * @throws IOException If anything goes wrong
     */
    protected void copy(InputStream input, OutputStream output) throws IOException {
        final byte[] buffer = new byte[4096];
        int n;
        while (-1 != (n = input.read(buffer))) {
            output.write(buffer, 0, n);
        }
        output.flush(); // WW-1526
    }

    /**
     * Look for a static resource in the classpath.
     *
     * @param name The resource name
     * @param packagePrefix The package prefix to use to locate the resource
     * @return The inputstream of the resource
     * @throws IOException If there is a problem locating the resource
     */
    protected InputStream findInputStream(String name, String packagePrefix) throws IOException {
        String resourcePath;
        if (packagePrefix.endsWith("/") && name.startsWith("/")) {
            resourcePath = packagePrefix + name.substring(1);
        } else {
            resourcePath = packagePrefix + name;
        }

        resourcePath = URLDecoder.decode(resourcePath, encoding);

        return ClassLoaderUtil.getResourceAsStream(resourcePath, getClass());
    }
}