在空響應

Question

這裏服務於請求的結果的PDF是從一個服務器獲取PDF和在servlet的服務於它作爲響應的代碼：

GAELogger.logInfo(LOG, "download request. url: " + downloadURLStr); 

HTTPResponse fetchResponse = URLFetchServiceFactory.getURLFetchService().fetch(new URL(downloadURLStr)); 

byte[] pdfContent = fetchResponse.getContent(); 
Integer totalLength = pdfContent.length; 
String fileName = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss").format(new Date()); 

GAELogger.logInfo(LOG, "writing. total: " + totalLength.toString()); 

response.reset(); 
response.setStatus(HttpServletResponse.SC_OK); 
response.setContentType("application/pdf"); 
response.addHeader("Content-Disposition", "attachment; filename=\"" + fileName + ".pdf\""); 
response.setHeader("Content-Length", totalLength.toString()); 

ServletOutputStream outputStream = response.getOutputStream(); 
outputStream.write(pdfContent); 
outputStream.flush(); 
outputStream.close(); 

GAELogger.logInfo(LOG, "done."); 

這裏是日誌請求的服務PDF：

download request. url: http://someurl/test.pdf 
writing. total: 43497 
logInfo: done. 

，有時響應是空的和鉻給出這樣的錯誤：

雖然有時它確實服務於請求並下載了pdf。我已經嘗試了多種方案，例如：

String downloadURLStr = outputFiles.get(0).getUrl(); 
URL downloadURL = new URL(downloadURLStr); 
URLConnection connection = downloadURL.openConnection(); 

InputStream inputStream = downloadURL.openStream(); 
OutputStream outputStream = response.getOutputStream(); 
Integer totalLength = connection.getContentLength(); 

response.setContentType("application/pdf"); 
response.addHeader("Content-Disposition", "inline; filename=\"" + id + ".pdf\""); 
response.setHeader("Content-Length", totalLength.toString()); 

IOUtils.copy(inputStream, outputStream); 

IOUtils.closeQuietly(inputStream); 
IOUtils.closeQuietly(outputStream); 

這也失敗了。任何想法爲什麼？

Answer 1

我沒有很長一段時間做谷歌App Engine的東西，但當時（也許2年前）的GAE關閉線程，如果他們花了太長時間。也許你應該仔細檢查GAE的限制，如果它們導致這種奇怪的行爲。然而，這將回答爲什麼它有時工作，有時不工作。