JSP：已为此响应调用 getOutputStream()

我正在使用此代码从 FTP 下载文件。 我在 tomcat 日志中遇到异常，如下所示，我能够执行我的任务，但我的日志大小增加了很多。

Code:

   if (file.exists())
   {
       if (file.canRead())
       {
          // IE6 & SSL PDF Bug
          // http://forums.sun.com/thread.jspa?threadID=526451&start=15&tstart=0

           mimeType = new javax.activation.MimetypesFileTypeMap().getContentType(file);
           response.setHeader("Cache-Control","private");
           response.setHeader("Pragma","expires");
           response.setHeader("Content-Disposition", "inline; filename=\"" + org.apache.commons.io.FilenameUtils.getName(file.getAbsolutePath()) + "\"");
           response.setContentType(mimeType);
           response.setContentLength((new Long(file.length())).intValue());
           byte[] buffer = new byte[(int)org.apache.commons.io.FileUtils.ONE_KB * 64];
           output=response.getOutputStream();
           bos = new java.io.BufferedOutputStream(output, buffer.length);
           bis = new java.io.BufferedInputStream(new java.io.FileInputStream(file));
           while (bis.read(buffer) != -1)
           {
               bos.write(buffer);
           }
           bos.flush();
       }
       else{System.out.println("Cannot read from file");}
   }
   else{System.out.println("File dosen't exist");}

错误信息

    Jan 18, 2014 6:11:31 AM org.apache.catalina.core.StandardWrapperValve invoke
SEVERE: Servlet.service() for servlet jsp threw exception
 java.lang.IllegalStateException: getOutputStream() has already been called for this response
at org.apache.catalina.connector.Response.getWriter(Response.java:611)
at org.apache.catalina.connector.ResponseFacade.getWriter(ResponseFacade.java:198)
at org.apache.jasper.runtime.JspWriterImpl.initOut(JspWriterImpl.java:125)
at org.apache.jasper.runtime.JspWriterImpl.flushBuffer(JspWriterImpl.java:118)
at org.apache.jasper.runtime.PageContextImpl.release(PageContextImpl.java:188)
at org.apache.jasper.runtime.JspFactoryImpl.internalReleasePageContext(JspFactoryImpl.java:118)
at org.apache.jasper.runtime.JspFactoryImpl.releasePageContext(JspFactoryImpl.java:77)

我看到有关向 servlet 添加代码以及关闭输出流的帖子，但这些都不起作用。请协助。

你不应该在 JSP 中这样做，但你应该使用 Servlet（即使 jsp 页面更实用）

但是，如果您仍然想使用 jsp 页面，请使用以下指令：

<%@page language="java" trimDirectiveWhitespaces="true"%>

除了问题之外，因为您使用的是 commons-io：

if (file.exists())
{
    if (file.canRead())
    {
       // IE6 & SSL PDF Bug
       // http://forums.sun.com/thread.jspa?threadID=526451&start=15&tstart=0

        mimeType = new javax.activation.MimetypesFileTypeMap().getContentType(file);
        response.setHeader("Cache-Control","private");
        response.setHeader("Pragma","expires");
        response.setHeader("Content-Disposition", "inline; filename=\"" + org.apache.commons.io.FilenameUtils.getName(file.getAbsolutePath()) + "\"");
        response.setContentType(mimeType);
        response.setHeader("Content-Length", String.valueOf(file.length()));

        OutputStream output = response.getOutputStream();
        FileUtils.copyFile(file, output);
        output.close();
    }
    else{System.out.println("Cannot read from file");}
}
else{System.out.println("File dosen't exist");}