java - Servlet 混合 header 和内容并在输出中写入相同的两次？

Question

我已经实现了行为不稳定的 servlet，有时它会在内容中混合 header 并写入相同的内容两次。

有时它返回的文件包含混合了如下内容的响应 header :

Server: Apache-Coyote/1.1
: W/"43-1353687036000"
DatCCoonntenntt--DDiissppoosittiioonn: : atatatacehnmte;n tf;i lfenlaemnea=m20=12201112211127325421_4W1_Wirnkgi_nSgc_Seern.xnlsx
sx
Content-Typ-eT: ype: applaipcatciaoti/on/toctestt-rstare
am
ConCtoententy-pTeype: appalicatcion/oon/octet-setarm
m
CCoonntent-Lnegtht h: 4199

Date: te: FriF,r i2,3  2No vNo2v0 120162: 215:25 :G4M2T 
....
File content bytes ...

And again same header and content

更新*这种情况发生在Tomcat7上*

我也在 Tomcat6 和 Jetty 上进行了测试，在这两种情况下都没有向响应内容注入(inject) HTTP-Header，但是 HTTP-Header 是错误的并返回错误的文件名，文件内容是正确的文件。我注意到 servlet 的错误返回发生在返回传输编码是分块的。

当我删除标题内容和字节的第二部分时，它是有效文件。有没有可能是同步问题？

更新这是 servlet 的完整源代码:

public class ExcelDownloadServlet extends HttpServlet
{
    private static final long serialVersionUID = 1L;
    private static final Logger LOG = Logger
            .getLogger (ExcelDownloadServlet.class);


    @Override
    protected void doGet (HttpServletRequest request,
            HttpServletResponse response) throws ServletException, IOException
    {
        try
        {
            TransactionId transactionId = getTransactionId (request);
            String fileName =
                    request.getParameter (GlobalConstants.EXCEL_FILE);
            ExcelDownloadType downloadType =
                    ExcelDownloadType
                            .valueOf (request
                                    .getParameter (GlobalConstants.EXCEL_DOWNLOAD_TYPE));
            ActionContextFactory actionContextFactory =
                    ApplicationContext.getContext ()
                            .getActionContextFactory ();
            //suppress warning. HttpServletRequest.getLocales does not support generics
            @SuppressWarnings("unchecked")
            ActionContext actionContext =
                    actionContextFactory.create (request.getSession ()
                            .getId (), Collections.<Locale> list (request
                            .getLocales ()));
            GetExcelDataResponse dataResponse =
                    new GetExcelData (transactionId, fileName, downloadType)
                            .execute (actionContext);
            writeToResponse (response, dataResponse.getFileName (),
                    dataResponse.getData ());
        }
        catch (InvalidSessionException e)
        {
            LOG.error ("Invalid session in Excel download", e);
            throw new ServletException (e);
        }
        catch (ActionException e)
        {
            LOG.error ("Could not download into excel.", e);
            throw new ServletException (e);
        }
    }

    protected TransactionId getTransactionId (HttpServletRequest request)
    {
        return RequestParameterDeserializer.<TransactionId> deserialize (
                request, GlobalConstants.TRANSACTION_ID);
    }

    protected void writeToResponse (HttpServletResponse response,
            String rawFileName, byte[] data) throws IOException
    {
        ServletOutputStream sout = null;
        try
        {            
            response.setContentType ("application/octet-stream");
            response.setContentLength (data.length);
            // removing blanks from the file name, since FF cuts file names
            // otherwise.
            String fileNameWithTime = rawFileName.replaceAll (" ", "_");
            response.setHeader ("Content-Disposition", "attachment; filename="
                    + fileNameWithTime);
            sout = response.getOutputStream ();
            sout.write (data, 0, data.length);
        }
        finally
        {
            if (sout != null)
            {
                sout.close ();
            }
        }
    }

更新*调用来自 GWT 应用程序，当生成带有所需参数的 servlet 的 URL 并在 IFrame 中设置时，然后调用 servlet 并下载文件。有什么建议吗？*

Answer 1

很久以前我也遇到过类似的问题。事实证明，关闭 ServletOutputStream 会触发请求流上的意外行为。

Servlet 不应该关闭容器提供的 OutputStream。另一个问题可能是手动设置内容长度，这是容器产生正确值的责任。

总而言之，尝试删除 out.close() 和 response.setContentLength()