表单向Servlet发送空查询字符串

Question

I have a JSP that has a form that looks like this:

<form method="GET" action="ManagerLogicServlet?action=salesreport" >
                <select name="monthList">
                    <option value="1">January</option>
                    <option value="2">February</option>
                    <option value="3">March</option>
                    <option value="4">April</option>
                    <option value="5">May</option>
                    <option value="6">June</option>
                    <option value="7">July</option>
                    <option value="8">August</option>
                    <option value="9">September</option>
                    <option value="10">October</option>
                    <option value="11">November</option>
                    <option value="12">December</option>
                </select>
                <input type="submit" value="Submit">
    </form>

I am trying to send over a query string with attribute action = salesreport which will be a condition that will return a sales report for the selected month (don't mind the missing default value). I submit the form over to the ManagerLogicServlet which has this code snippet:

..String action = request.getParameter("action");

    if (action.equalsIgnoreCase("salesreport")){

        forward = SALES_REPORT;
        int month = Integer.parseInt(request.getParameter("monthList"));
        String monthString = new DateFormatSymbols().getMonths()[month-1];
        request.setAttribute("monthString", monthString);
        request.setAttribute("salesReport", salesDAO.getSalesReport(month));

    } else if..

But the action attribute is set to null. Why is this?

Answer 1

Because your form is using the GET method, the parameters from the action attribute are being discarded. If you insist on using GET , then you can include an <input> tag containing the parameter you wish to pass on to the servlet. Try doing this:

<form method="GET" action="ManagerLogicServlet?action=salesreport" >
    <input type="hidden" name="action" value="salesreport">
    <select name="monthList">
        <option value="1">January</option>
        ...
    </select>
    <input type="submit" value="Submit">
</form>

The alternative would be for you to leave your code as is, but change the form's method to POST .

Answer 2

Its working fine. I tried this

HTML

    <form action="AnyServlet?action=salesreport" method="post">
        <input type="submit" value="Submit Data" />
    </form>

AnyServlet.java

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String action = request.getParameter("action");
        System.out.println("action=="+action);


        }

Output

action==salesreport

UPDATE

When i changed from "post" to "get",I am getting issue too.You can use hidden input field if you want go with "get".