java - Convenient way to parse incoming multipart/form-data parameters in a Servlet

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Answer 1

multipart/form-data encoded requests are indeed not by default supported by the Servlet API prior to version 3.0. The Servlet API parses the parameters by default using application/x-www-form-urlencoded encoding. When using a different encoding, the request.getParameter() calls will all return null. When you're already on Servlet 3.0 (Glassfish 3, Tomcat 7, etc), then you can use HttpServletRequest#getParts() instead. Also see this blog for extended examples.

Prior to Servlet 3.0, a de facto standard to parse multipart/form-data requests would be using Apache Commons FileUpload. Just carefully read its User Guide and Frequently Asked Questions sections to learn how to use it. I've posted an answer with a code example before here (it also contains an example targeting Servlet 3.0).