如何从一个servlet发送一个文件的“正确”办法？ [英] How to send a file from a servlet the "right" way?

问题描述

我试图从一个http servlet发送一个文件给用户。
servlet运行一些鉴别测试（在请求上），然后发送给客户端一个文件。

这个通用工作，但现在我打开我的TOMCAT服务器重定向到https，当我尝试访问该servlet并从IE6或IE8下载文件失败，我得到这个例外：

  java.lang.IllegalStateException：提交响应后无法转发
  

（在localhost.log中）

和

  ClientAbortException：java.net.SocketException：连接重置通过peer：socket写入错误
  

（在servlet日志中）

发送的代码（简体）：

  private void sendFile（HttpServletResponse response，byte []文件，字符串clientFileName）
 {
 ServletOutputStream op = null; 
 
 setContentType（response）; 
 response.setHeader（Content-Disposition，attachment; filename = \+ clientFileName +\）; 
 //发送字节数组到输出缓冲区。 
 op = response.getOutputStream（）; 
 
 //完成所有处理后，内容长度必须设置。 
 response.setContentLength（（int）file.length）; 
 op.write（file）; 
 
 
 
 $ b 
这是从servlet发送文件的正确方法吗？最好的方法是什么？
 
 
 
感谢!!  
 
 
 更新 
 
 
 
在此链接中使用@BalusC artice中的代码：
  http://balusc.blogspot.com/2007/07/fileservlet.html  
 
 
 
这使它工作。
 
 
 
在Gmail中使用IE6-IE8时仍然不起作用，因为gmail会在这些浏览器中添加下载过滤功能。
 
 
 
 更新2  
 
 
 
这个问题似乎与Gmail + Internet Explorer 6-8有关。 
我假设Gmail正在做一个重定向（这实际上很明显，如果你点击邮件中的链接后，在页面上的网址）。 
客户端拉技术是我唯一的解决方案吗？解决方案

技术。
通过在头文件中添加 Refresh 值，我们让浏览器询问文件。

是唯一可以解决的问题，克服了gmail在按下电子邮件链接时使用重定向的问题。

在代码中，我这样做了： / p>

  response.setHeader（Refresh，3; URL = \+ url.toString（）+\ ）; 
 forwardToJSP（request，response，waitForBrowserRefreshPage.jsp）; 
  

含义 - 3秒后询问用户指定的url，然后将文件传递到文件给客户。
forwardToJSP 方法显示您将很快转发，这里是一个链接，如果失败的消息。

I'm trying to send a file to a user from an http servlet. The servlet runs some identification tests (on the request) and then sends the client a file.

This generally works but now I turned on my TOMCAT server redirects to https and when I try to access the servlet and download the file from either IE6 or IE8 it fails and I get this exception:

java.lang.IllegalStateException: Cannot forward after response has been committed

(on the localhost.log)

and

ClientAbortException:  java.net.SocketException: Connection reset by peer: socket write error

(in the servlet log)

The code that does the sending (Simplified):

private void sendFile(HttpServletResponse response, byte[] file, String clientFileName)
{
    ServletOutputStream op = null;

    setContentType(response);
    response.setHeader("Content-Disposition", "attachment; filename=\"" + clientFileName + "\"");
    // send byte array to output buffer. 
    op = response.getOutputStream();

    // Content Length must be set after all processing done.
    response.setContentLength((int) file.length);   
    op.write(file);
}

Is this the correct way to send a file from a servlet? What's the best way?

Thanks!!

UPDATE

Used the code from @BalusC artice in this link: http://balusc.blogspot.com/2007/07/fileservlet.html

This made it work.

Still doesn't work in IE6-IE8 when used from Gmail because of a filtering stage gmail adds to downloads in these browsers.

UPDATE 2

The problem seems to be with Gmail + Internet Explorer 6-8. I'm Assuming that gmail is doing a redirect (That's actually pretty obvious if you look at the url on the page after you click the link in the mail). Is Client-Pull technique my only solution?

解决方案

The solution to the problem is the "Client-Pull" technique. By adding a Refresh value to the header we make the browser ask for the file.

This is the only solution I could come up to that overcomes the fact the gmail will use redirection when pressing a link from within an email.

In the code I did this:

response.setHeader("Refresh", "3; URL=\"" + url.toString() + "\"");
forwardToJSP(request, response, "waitForBrowserRefreshPage.jsp");

Meaning - after 3 seconds ask the user for the specified url which will, in turn, deliver the file to the client. The forwardToJSP method displays the "You will be forwarded soon, here a link if it fails" message.

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