使用PDFBox和Java Filter Servlet在下载PDF文件之前向其添加头

我试图在向客户端显示之前向PDF文件添加标题。我有一个过滤器servlet，它将在应用程序请求保存之前拦截请求/响应。我已经在一个独立的PDF上测试了我的PDFBox类，这很有效。我在使用过滤器Servlet时遇到困难。我尝试了HttpServletRequestWrapper，但无法获得eh inputstream。它似乎是空的。这是我的过滤代码：

public class AddFOUOFilterServlet implements Filter {
/** The log. */
private static Log log = LogFactory.getLog(AddFOUOFilterServlet.class);

private String loginUrl = null;

/**
 * @desc - This function initializes the global variables.
 * @param filterConfig - FilterConfig settings that come from the web.xml
 */
public void init(FilterConfig filterConfig) throws ServletException {
    log.debug("Inside AddFOUOFilterServlet init ");
    ServletContext context = filterConfig.getServletContext();
} 

/**
 * @desc - the method called by the server before each server request
 * @param req - the servlet request
 * @param res - the servlet response
 * @param chain - a FilterChain object that lists all filters to be called by the server
 * @throws IOException, ServletException
 */
public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException { 
    //log.debug("Inside doFilter");

    // cast the HTTP request and response objects and get the url path info
    HttpServletRequest request = (HttpServletRequest)req; 
    HttpServletResponse response = (HttpServletResponse)res;  
    HttpServletRequestWrapper requestWrapper = new HttpServletRequestWrapper(request);
    InputStream is = request.getInputStream();
        log.debug("is.available() "+is.available());
        byte[] buf = new byte[1024];
        while((is.read(buf))>0) {
            log.debug("Reading the InputStream from the wrapper ");
    }
    if (request.getParameter("DocumentName") != null && request.getParameter("BlobID") != null)
    {
        log.debug("Processing the PDF URIs... ");
    try 
    {   
            AddFOUOToReport addfouo = new AddFOUOToReport();
            OutputStream os = null;
            os = addfouo.doIt(is, "For Official Use Only");
            chain.doFilter(requestWrapper, res);
    }
    catch (IOException ex)
    {
        log.error("AddFOUOToReport Filter error: " + ex.getMessage());
        response.sendRedirect(loginUrl); 
    } catch (COSVisitorException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    } else {
        chain.doFilter(req, res);
    }

}

public void destroy() {log.info("Inside destroy");  }

}

Web.xml条目：

    <!-- BEGIN AddFOUOFilter Changes  -->
<filter>
    <filter-name>AddFOUO Filter</filter-name>
    <filter-class>com.jmar.bo.controller.AddFOUOFilterServlet</filter-class>
</filter>
<filter-mapping>
    <filter-name>AddFOUO Filter</filter-name>
    <url-pattern>/cdz/*</url-pattern>
</filter-mapping>
<filter-mapping>
    <filter-name>AddFOUO Filter</filter-name>
    <url-pattern>/cdzServlet?getBlob*</url-pattern>
</filter-mapping>
<filter-mapping>
    <filter-name>AddFOUO Filter</filter-name>
    <url-pattern>/*</url-pattern>
</filter-mapping>
<!-- END AddFOUOFilter Changes -->

AddFOUO过滤器
com.jmar.bo.controller.AddFOUOFilterServlet
AddFOUO过滤器
/cdz/*
AddFOUO过滤器
/cdzServlet？getBlob*
AddFOUO过滤器
/*

---

没有唯一的模式来捕获此事件，这就是我使用as/*as模式的原因。

如果

InputStream

为空，则表示浏览器没有发送PDF

---

我猜PDF不是来自浏览器，而是来自服务器…

感谢您的快速回复，这是正确的PDF来自服务器。这看起来像是在文件准备好之前过滤器触发。不，您正在从

请求

读取

输入流

，这是浏览器发送的。这不是正确的方法。我尝试了响应对象包装器，但没有getInputstream。如果我使用的是过滤器servlet，那么对该过滤器的请求应该具有文件权限？你对正确的方法有什么建议吗？感谢您的时间。请参阅“为自定义请求和响应编程”一节。