java - Passing value to servlet from image -

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from jsp have

.. <form action="testmartcontroller" method="post"> <input type="hidden" value="math"> <input type="image" src="<%=request.getcontextpath()%>/css/categories/math.jpg"> </form> ..

in servlet have

... private static final string math = "web-inf/jsp/math.jsp";  protected void dopost(httpservletrequest request, httpservletresponse response) throws servletexception, ioexception {          string forward = null;          string action=request.getparameter("action");         if(action.equals("math")){         forward = math;         flag = 1;         }         requestdispatcher rd = request.getrequestdispatcher(forward);         rd.forward(request, response); } ...

when clicked image got null pointer exception. want know why not pass value should. since hidden values pass.

your input type="hidden" field missing name="action" attribute. thus, action parameter null.


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