Q:I'm using FileUpload in an Action, but it's not working. Why?
A:Struts recognises multipart requests, and parses them automatically, presenting the request parameters to your code in the same manner as if they were regular request parameters. Since Struts has already processed the request, and made it available in your form bean, the input stream is no longer available for parsing, so attempting to do so with FileUpload will fail.
Q:But I need to parse the request myself. How can I do that?
A:Struts parses multipart a request as a part of the process of populating your form bean from that request. If, for some reason, you need to have full control over the multipart parsing, you can do so by configuring your action mapping without an associated form bean. (A better way of doing this, however, is to replace the default multipart handler with your own. See the Struts documentation for details.)
请问怎么 replace the default multipart handler with your own