问题描述
如何判断用户在从Java Servlet下载过程中是否被取消？似乎对我来说，IE，输出流println（）阻塞。使用的命中取消，但是有没有办法时间这样或这样的事情？
How can you tell if the user hit cancel during a download from a Java servlet? What seem to happen for me with IE, the output stream println() blocks. The used hit cancel, but is there a way to time this out or anything like that?
推荐答案
包裹 OutputStream＃write（）， #flush（）和 #close（） try-catch 阻止 IOException 。如果被捕获，那么通常意味着最终用户已经中止请求。
Wrap OutputStream#write(), #flush() and #close() in a try-catch block on IOException. If caught, then it usually means that the enduser has aborted the request.
为了进一步了解，您还可以捕获更多的servlet容器特定异常，如在Tomcat和克隆（这是 IOException 的子类），但这将使您的webapp代码不能与其他servlet容器。
To get a step further, you could also catch on a more servletcontainer-specific exception like ClientAbortException on Tomcat and clones (which is a subclass of IOException), but this will make your webapp code unportable to other servletcontainers.
更新：要回覆屏蔽问题，您可以致电 flush（）在写入单个数据块之后。这将使实际将数据发送给客户端，并在底层套接字关闭时导致 IOException 。
Update: to come back on the blocking issue, you'd like to call flush() after writing a single block of data. This will actually send the data to the client and cause IOException when the underlying socket is closed.
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