getParameter的空返回值（Tomcat Servlet）

Question

I am trying to get the value of a checkbox from a posted form data. I already have the form working because I can get the value of a file easily enough(I have omitted the file form field in the code below), but the checkbox wont return anything other than null. What am I doing wrong?

Servlet:

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    String str = request.getParameter("isTransform");

    System.out.println("parameter: " + str);
}

Html Client:

<form enctype="multipart/form-data" id="compareForm1" >
    <input type="checkbox" value="true" name="isTransform" id="isTransform1" >
</form>

I have jquery.form.js sending the actual post

var options = {
                url:          "http://localhost:8080/TestingTomcat/someClassName",
                type:         "POST",
                success:      function (html){
                    $("#placeholder").html(html);
                    change_active("comparison_page");
                }
        };

        $("#compareForm1").submit(function () {
            $(this).ajaxSubmit(options);

            return false;
        });

Actual Post data:

POSTDATA =-----------------------------153501500631101
Content-Disposition: form-data; name="isTransform"

true
-----------------------------153501500631101
Content-Disposition: form-data; name="isTransform"

true
-----------------------------153501500631101--

And the result I get with the button clicked or unclicked is:

parameter: null

Answer 1

Parameters post from 'multipart/form-data' form can not be get from getParameter method. You should use 3rd-party library to handle the multipart data for parse the content of req.getInputStream() by yourself. I think Apache Commons fileUpload will help you.