How to retrieve a parameter in a java servlet

Question

I have searched multiple places but couldn't quite find what I need. I am new to servlets and html and pretty sure I am missing something simple.

I have one servlet servletA in it's doGet, I do the following:

response.setContentType("text/html");

PrintWriter out = response.getWriter();
StringBuilder sb = new StringBuilder();
sb.append("<html><head></head><body>");
sb.append("<div><select name=\"thisparameter\">");
ArrayList<A> list = helper.getList(); 
sb.append("<option value=\"select\">Select an option</option>");
for (int i=0; i<list.size(); i++) {
   A a = list.get(i);
   sb.append("<option value="+ a.getYear()+">" + a.getName() + "</option>");
}
sb.append("</select>");
sb.append("<form action=\"servletB\" method=\"GET\">\n" +
"    <button type=\"submit\">Go</button>\n" +
"</form></div>");

sb.append("</body>");
sb.append("</html>");
out.println(sb.toString());
out.close();

In servletB's doGet()

PrintWriter out = response.getWriter();
StringBuilder sb = ServletHelper.getHeaderHtml();

response.setContentType("text/html");

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

The string thisparameter is always null. I tried with POST and got the same result. I would really like to use only servlets and not a combination with JSP. Any help would be highly appreciated. Thank you.

score 0 · Accepted Answer · answered Jul 31 '16 at 16:54

Your select needs to be inside the form to be able to be submitted to the servlet. To make it happen, change your code like so.

PrintWriter out = response.getWriter();
StringBuilder sb = new StringBuilder();
sb.append("<html><head></head><body>");
sb.append("<form action=\"servletB\" method=\"GET\">");
sb.append("<div><select name=\"thisparameter\">");
ArrayList<A> list = helper.getList(); 
sb.append("<option value=\"select\">Select an option</option>");
for (int i=0; i<list.size(); i++) {
   A a = list.get(i);
   sb.append("<option value="+ a.getYear()+">" + a.getName() + "</option>");
}
sb.append("</select>");
sb.append("<button type=\"submit\">Go</button>\n" +
"</form></div>");

sb.append("</body>");
sb.append("</html>");
out.println(sb.toString());
out.close();

@user2237511 If it works for you, can you mark the answer as accepted? — Pradeep Pati, Jul 31 '16 at 16:59
yeah I was meaning to, it was too soon to accept kept telling me to try after some time :) — user2237511, Jul 31 '16 at 17:16

How to retrieve a parameter in a java servlet

1 Answers1