RE: Concepts in working with multipart request

[SCHACHTER,MICHAEL (HP-NewJersey,ex2)]

Jonathan,      > Hello all.  > I wanted to know if I am able to use the MultipartRequestWrapper object by itself.   > That is, can I store MultipartRequestWrapper objects in a bean.    I would definately not recommend it.  The MultipartRequestWrapper object is something that should be used internally to Struts, to work around some existing issues between normal and multipart requests.  Also, that class is definately going to change to extend javax.servlet.http.HttpServletRequestWrapper when Struts adopts the Servlet 2.3 spec.    > My purpose is to temporarily store a binary and its file name in a bean until  > the final form page when the user  submits   the whole "kit and kaboodle".    Instead of doing this, you'd probably just want to stick to using an ActionForm bean that has a FormFile property.  The FormFile interface should suit your needs well, as it has a getFileName() method and methods to retrieve the data written to a temporary file after uploading:   public class MultipageForm extends ActionForm {      private FormFile theFile;        public void setTheFile(FormFile file) {           this.theFile = file;       }      public FormFile getTheFile() {           return theFile;      } }    > Part of the problem is that I dont understand what is going on. It looks like the request keeps the following:  > "name" property representing the form field name  > "value" property representing the String path of the file you uploaded  > some binary Stream data representing the file    Again, don't pay much attention to the MultipartRequestWrapper class, concentrate on creating an ActionForm bean that has a org.apache.struts.upload.FormFile property representing your file, and normal String properties representing your form data, just as you would normally create a non multipart form.    > I realy have no idea, and I am looking around for answers but am coming up empty.  > Can someone sum up what is happening here, what the request contains, what values the request  > works with, and what   are the requirements.    Martin Cooper summed this up nicely in another thread about uploading, but I'll go over it anyway:   1) Request comes in, Struts goes to populate the form (BeanUtils.populate()) discovers that the     content type of the request is "multipart/form-data" 2) Struts goes to populate the form, and creates a MultipartRequestHandler instance to handle     the multipart request.  MultipartRequestHandler is an interface, the implementation can change     at will and can be specified as an init-param for ActionServlet, or as an ActionServlet property     in struts-config.xml      2a) In the implementation that comes with Struts, the multipart form data is read as follows:       Read the data,         if it's a string parameter, grab it's value and put it in a Hashtable for later use         if it's a file, read the file with a BufferedInputStream and store the data in a temporary         file, then wrap it in a FormFile implementation (org.apache.struts.upload.DiskFile)         and hand it back to BeanUtils (next step)  3) BeanUtils.populate() uses the interface methods in MultipartRequestHandler to grab the properties     that were retrieved from the normal multipart request, the populates your ActionForm bean with the     relevant data. 4) The Action is executed, and code in there manipulates the file according to whatever you want to     do with it, for example, say we wanted to take the previous form bean (above) and use it in the action:     public class UploadAction extends Action {     public ActionForward perform(ActionMapping mapping,                                  ActionForm form,                                  HttpServletRequest request,                                  HttpServletResponse response) {            FormFile theFile = ((MultipageForm) form).getTheFile();            String filename = theFile.getFileName();            //and so on... }   Hope this helps, also consult that long thread called "uploading files requires immediate serialization?", Martin Cooper does a damn good job of answering questions about this.  Thanks again Martin...   - Mike