Question

I´m trying to catch the next two highlighted fields in a servlet where I can get the uploaded file.

The source code is just the same as which is shown in a GWT FormSubmit class Javadoc

form.setEncoding(FormPanel.ENCODING_MULTIPART);
form.setMethod(FormPanel.METHOD_POST);

// Create a panel to hold all of the form widgets.
VerticalPanel panel = new VerticalPanel();
form.setWidget(panel);

// Create a TextBox, giving it a name so that it will be submitted.
final TextBox tb = new TextBox();
tb.setName("WorkTitle");
tb.setValue("WorkTitle");

panel.add(tb);

// Create a ListBox, giving it a name and some values to be associated
// with
// its options.
ListBox lb = new ListBox();
lb.setName("listBoxFormElement");
lb.addItem("foo", "fooValue");
lb.addItem("bar", "barValue");
lb.addItem("baz", "bazValue");
panel.add(lb);

// Create a FileUpload widget.
FileUpload upload = new FileUpload();
upload.setName("uploadFormElement");
panel.add(upload);

// Add a 'submit' button.
panel.add(new Button("Submit", new ClickListener() {
    public void onClick(Widget sender) {
        form.setAction(GWT.getModuleBaseURL()+"uploadWork");
        form.submit();
    }
}));

I´m getting these parameters with this code lines in my servlet:

protected void doPost(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
    System.out.println("ENTRAA BIENNNN");
    System.out.println(" ___ELEMENTO1" + req.getAttribute("WorkTitle"));
    System.out.println(" ___ELEMENTO3" + req.getParameterValues("WorkTitle"));

But both returns me NULL.

How could I do?

TIA!

Answer 1

Most servlet containers do not decode multipart/form-data automatically, so req.getParameter (or getParameterValues or similar getters) won’t return anything.
You’ll have to use a library such as Apache Commons FileUpload, or Jetty’s MultiPartFilter to decode multipart/form-data payload.

As a side note, req.getAttribute has nothing to do with getting data out of the request; it’s used to pass data, related to a request, between server components (between the servlet container and servlets, or between a filter and a servlet, for instance)