Java HttpServletResponse.SC_NOT_MODIFIED屬性代碼示例

/**
 * Performs a number of checks to ensure response saneness according to the rules of RFC2616:
 * <ol>
 * <li>If the response code is {@link javax.servlet.http.HttpServletResponse#SC_NO_CONTENT} then it is illegal for the body
 * to contain anything. See http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.2.5
 * <li>If the response code is {@link javax.servlet.http.HttpServletResponse#SC_NOT_MODIFIED} then it is illegal for the body
 * to contain anything. See http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.3.5
 * </ol>
 *
 * @param request        the client HTTP request
 * @param responseStatus the responseStatus
 * @return true if the response should be 0, even if it is isn't.
 */
public static boolean shouldBodyBeZero(HttpServletRequest request, int responseStatus) {

    //Check for NO_CONTENT
    if (responseStatus == HttpServletResponse.SC_NO_CONTENT) {
        if (LOG.isDebugEnabled()) {
            LOG.debug("{} resulted in a {} response. Removing message body in accordance with RFC2616.",
                    request.getRequestURL(), HttpServletResponse.SC_NO_CONTENT);
        }
        return true;
    }

    //Check for NOT_MODIFIED
    if (responseStatus == HttpServletResponse.SC_NOT_MODIFIED) {
        if (LOG.isDebugEnabled()) {
            LOG.debug("{} resulted in a {} response. Removing message body in accordance with RFC2616.",
                    request.getRequestURL(), HttpServletResponse.SC_NOT_MODIFIED);
        }
        return true;
    }
    return false;
}
 

void checkChunking(HttpResponseImpl response) {
    // If any data has already been written to the stream, we must not
    // change the chunking mode
    if (count != 0)
        return;
    // Check the basic cases in which we chunk
    useChunking =
        (!response.isCommitted()
         && response.getContentLength() == -1
         && response.getStatus() != HttpServletResponse.SC_NOT_MODIFIED);
    if (!response.isChunkingAllowed() && useChunking) {
        // If we should chunk, but chunking is forbidden by the connector,
        // we close the connection
        response.setHeader("Connection", "close");
    }
    // Don't chunk is the connection will be closed
    useChunking = (useChunking && !response.isCloseConnection());
    if (useChunking) {
        response.setHeader("Transfer-Encoding", "chunked");
    } else if (response.isChunkingAllowed()) {
        response.removeHeader("Transfer-Encoding", "chunked");
    }
}
 

protected boolean doResponseRedirectOrNotModifiedLogic(HttpServletRequest servletRequest, HttpServletResponse servletResponse,
        HttpResponse proxyResponse, int statusCode) throws ServletException, IOException {
    // Check if the proxy response is a redirect
    // The following code is adapted from org.tigris.noodle.filters.CheckForRedirect
    if (statusCode >= HttpServletResponse.SC_MULTIPLE_CHOICES /* 300 */
            && statusCode < HttpServletResponse.SC_NOT_MODIFIED /* 304 */) {
        Header locationHeader = proxyResponse.getLastHeader(HttpHeaders.LOCATION);
        if (locationHeader == null) {
            throw new ServletException(
                    "Received status code: " + statusCode + " but no " + HttpHeaders.LOCATION + " header was found in the response");
        }
        // Modify the redirect to go to this proxy servlet rather that the proxied host
        String locStr = rewriteUrlFromResponse(servletRequest, locationHeader.getValue());

        servletResponse.sendRedirect(locStr);
        return true;
    }
    // 304 needs special handling. See:
    // http://www.ics.uci.edu/pub/ietf/http/rfc1945.html#Code304
    // We get a 304 whenever passed an 'If-Modified-Since'
    // header and the data on disk has not changed; server
    // responds w/ a 304 saying I'm not going to send the
    // body because the file has not changed.
    if (statusCode == HttpServletResponse.SC_NOT_MODIFIED) {
        servletResponse.setIntHeader(HttpHeaders.CONTENT_LENGTH, 0);
        servletResponse.setStatus(HttpServletResponse.SC_NOT_MODIFIED);
        return true;
    }
    return false;
}
 

@Override
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {

    HttpServletRequest httpRequest = (HttpServletRequest) request;
    HttpServletResponse httpResponse = (HttpServletResponse) response;

    if (!isIncluded(httpRequest) && acceptsGZipEncoding(httpRequest) && !response.isCommitted()) {
        // Client accepts zipped content
        if (log.isTraceEnabled()) {
            log.trace("{} Written with gzip compression", httpRequest.getRequestURL());
        }

        // Create a gzip stream
        final ByteArrayOutputStream compressed = new ByteArrayOutputStream();
        final GZIPOutputStream gzout = new GZIPOutputStream(compressed);

        // Handle the request
        final GZipServletResponseWrapper wrapper = new GZipServletResponseWrapper(httpResponse, gzout);
        wrapper.setDisableFlushBuffer(true);
        chain.doFilter(request, wrapper);
        wrapper.flush();

        gzout.close();

        // double check one more time before writing out
        // repsonse might have been committed due to error
        if (response.isCommitted()) {
            return;
        }

        // return on these special cases when content is empty or unchanged
        switch (wrapper.getStatus()) {
            case HttpServletResponse.SC_NO_CONTENT:
            case HttpServletResponse.SC_RESET_CONTENT:
            case HttpServletResponse.SC_NOT_MODIFIED:
                return;
            default:
        }

        // Saneness checks
        byte[] compressedBytes = compressed.toByteArray();
        boolean shouldGzippedBodyBeZero = GZipResponseUtil.shouldGzippedBodyBeZero(compressedBytes, httpRequest);
        boolean shouldBodyBeZero = GZipResponseUtil.shouldBodyBeZero(httpRequest, wrapper.getStatus());
        if (shouldGzippedBodyBeZero || shouldBodyBeZero) {
            // No reason to add GZIP headers or write body if no content was written or status code specifies no
            // content
            response.setContentLength(0);
            return;
        }

        // Write the zipped body
        GZipResponseUtil.addGzipHeader(httpResponse);

        response.setContentLength(compressedBytes.length);

        response.getOutputStream().write(compressedBytes);

    } else {
        // Client does not accept zipped content - don't bother zipping
        if (log.isTraceEnabled()) {
            log.trace("{} Written without gzip compression because the request does not accept gzip", httpRequest.getRequestURL());
        }
        chain.doFilter(request, response);
    }
}