Not able to use getParameter in servlet due to Multipart form data

Question

I have few text boxes and 4 to 5 Buttons in my jsp page, based on the button click and data in the form i need to perform operations.

But I am not able to use request.getParameter() in my servlet

My JSP code :

    <form action="UsageEngine" method="post" target="console" enctype="multipart/form-data">
        <input class="form-control" type="file" multiple name="filepath"    
            required>
<br> <input class="form-control" type="text"
            name="Grepfilename" placeholder="Command Line.."><br>
        <!-- <input class="form-control" type="text" name="FileToBeDownloaded" placeholder="File to be Downloaded"><br> -->
        <select class="form-control" name="env">
            <option>pinDap75a</option>
            <option>pinIap04a</option>
            <option>pinDap71a</option>
        </select><br>
        <button class="btn btn-danger" name="action" id="Irel"
            value="test" onclick="show()">Env Check</button>
        <button class="btn btn-success" name="action" value="process"
            onclick="show()">Process SFTP</button>
        <button class="btn btn-warning" name="action" id="grep" value="Grep"
            onclick="show()">Grep</button>
        <button class="btn btn-primary" name="action" id="Download"
            value="Download" onclick="show()">Init Irel</button>
        <button class="btn btn-info" name="action" id="Irel"
            value="completeIrel" onclick="show()">Complete Irel</button>
</form>

File upload is working fine. But I need to pass filename , environment details, and value of the button as well. For all these getParameter was very helpfull, but due to Multipart/form-data I am not able to use that.

upload.parseRequest(request); helps in listing down all the fields but I cannot use it for my application.

For my application it is like IF 1st button clicked{ do this function } , if s2nd Button{ do another action} like that.

Every Button tag has same name "Action" but with different value, so I read the value from the action and perform my function calls with if else conditions

COde :

 if (Action.equalsIgnoreCase("Grep")) {
            String Filenames = request.getParameter("Grepfilename");
            String[] GrepFileName = Filenames.split(",");
            try {
                for (int i = 0; i < GrepFileName.length; i++) {

                    GrepOutput.addAll(ExecEngine.ExecuteGrep(GrepFileName[i],
                            env));

                }

            } catch (JSchException e) {
                e.printStackTrace();
            } catch (SftpException e) {
                e.printStackTrace();
            } catch (InterruptedException e) {
                e.printStackTrace();
            } catch (ArrayIndexOutOfBoundsException e) {
                e.printStackTrace();
            }

            request.setAttribute("consoleOutputForSFTP", GrepOutput);
            request.getRequestDispatcher("/consoleOutput.jsp").forward(request,
                    response);
        } else if (Action.equalsIgnoreCase("Download")) {
            try {
                consoleOutputForSFTP = ExecEngine.deployIrelWrapper(env);
                request.setAttribute("consoleOutputForSFTP",
                        consoleOutputForSFTP);
                request.getRequestDispatcher("/consoleOutput.jsp").forward(
                        request, response);
            } catch (JSchException | InterruptedException e) {
                e.printStackTrace();
            }
        } else if (Action.equalsIgnoreCase("completeIrel")) {
            String GrepFileName = request.getParameter("Grepfilename");
            try {
                consoleOutputForSFTP = ExecEngine.deployFinalIrelWrapper(
                        GrepFileName, env);
                request.setAttribute("consoleOutputForSFTP",
                        consoleOutputForSFTP);
                request.getRequestDispatcher("/consoleOutput.jsp").forward(
                        request, response);
            } catch (JSchException | InterruptedException e) {
                e.printStackTrace();
            }

Answer 1

Assuming that you are using Apache Commons FileUpload to process the multipart data, you get a List<FileItem> from upload.parseRequest(request). However, FileItem has a method isFormField() to check if the field (use getFieldName() to retrieve its name) is a form field or not.

So, you have two options:

1. Iterate over the List<FileItem> until you found the appropriate paramter and its value.
2. Instead of using parseRequest(request) you could use parseParameterMap(request) with will return a Map<String,List<FileItem>> where the key should be the request parameter name from you html form. You then only need to take the value from the first element of the value's item.

Edit: Assuming that you can be parsing the multipart like this:

ServletFileUpload upload = new ServletFileUpload();
Map<String,List<FileItem>> paramMap = upload.parseParameterMap(request);

Then you can have a helper method like this which does the same as a request.getParameter(name), passing the paramMap as a parameter:

public String getParameterFromMap(String paramName, Map<String,List<FileItem>> map) {
    if ((paramName == null) || (map == null) || (map.isEmpty() == true)) {
        return null;
    }
    List<FileItem> items = map.get(paramName);
    if ((items == null) || (items.isEmpty() == true)) {
        return null;
    }
    FileItem firstItem = items.get(0);
    if ((firstItem == null) || (firstItem.isFormField() == false)) {
        return null;
    }
    return firstItem.getString();
}

Answer 2

In that case you can take a hidden variable to set the value of button clicked by javascript, and can fetch that hidden parameter value on servlet by item.getString() value.