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

Question

Is there any convenient way to read and parse data from incoming request   E g client initiate post request  URLConnection connection   new URL url  openConnection    connection setDoOutput true   connection setRequestProperty  Content-Type    multipart form-data  boundary     boundary   PrintWriter writer   null  try       OutputStream output   connection getOutputStream        writer   new PrintWriter new OutputStreamWriter output  charset   true      true   autoFlush  important         Send normal param      writer println  --    boundary       writer println  Content-Disposition  form-data  name   param          writer println  Content-Type  text plain  charset     charset       writer println        writer println param     I   m not able to get param using request getParameter  paramName    The following code  BufferedReader reader   new BufferedReader new InputStreamReader      request getInputStream        StringBuilder sb   new StringBuilder      for  String line   line   reader readLine       null        System out println line          however displays the content for me   -----------------------------29772313742745 Content-Disposition  form-data  name  name  J Doe -----------------------------29772313742745 Content-Disposition  form-data  name  email  abuse spamcop com -----------------------------29772313742745   What is the best way to parse incoming request  I don   t want to write my own parser  probably there is a  ready solution

User · Answer

Solutions   Solution A    Download http   www servlets com cos index html Invoke getParameters   on com oreilly servlet MultipartRequest   Solution B    Download http   jakarta Apache org commons fileupload  Invoke readHeaders   in  org apache commons fileupload MultipartStream   Solution C    Download http   users boone net wbrameld multipartformdata  Invoke getParameter on  com bigfoot bugar servlet http MultipartFormData   Solution D   Use Struts  Struts 1 1 handles this automatically   Reference  http   www jguru com faq view jsp EID 1045507

User · Answer

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

User · Answer

Not always there s a servlet before of an upload  I could use a filter for example   Or could be that the same controller   again a filter or also a servelt   can serve many actions  so I think that rely on that servlet configuration to use the getPart method  only for Servlet API    3 0   I don t know  I don t like    In general  I prefer independent solutions  able to live alone  and in this case  http   commons apache org proper commons-fileupload  is one of that    List lt FileItem gt  multiparts   new ServletFileUpload new DiskFileItemFactory    parseRequest request       for  FileItem item   multiparts            if   item isFormField                    your operations on file           else               String name   item getFieldName                String value   item getString                  you operations on paramters

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

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