How to get query parameters from HttpServletRequest (Tomcat 9.0)?

Question

The server recieves requests from two clients - Raspberry Pi and Android app, both send requests using HttpURLConnection. I need to pass parameters with theese requests, e.g:

http://192.168.0.10:8080/MyProject/MyServer/rpi/checktask?rpi="rpi"

doing it as:

String requestUrl = "http://192.168.0.10:8080/MyProject/MyServer/rpi";
String query = String.format("/checktask?rpi=%s",
                        URLEncoder.encode("rpi", "UTF-8"));
URL url = new URL(requestUrl + query);
conn = (HttpURLConnection) url.openConnection();
conn.setRequestMethod("GET");
conn.setDoInput(true);
conn.setRequestProperty("Accept-Charset", "UTF-8");
conn.connect();

The Servlet has annotation:

@WebServlet(name = "MyServer", urlPatterns = { "/MyServer/rpi/*", "/MyServer/app/*"})

But when Servlet gets request as above following happens:

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

String path = request.getRequestURI();     // /MyProject/MyServer/rpi/*
String query = request.getQueryString();   // null
String context = request.getContextPath(); // /MyProject
String servlet = request.getServletPath(); // /MyServer/rpi
String info = request.getPathInfo();       // /*
}

Although according to those answers: How to use @WebServlet to accept arguments (in a RESTFul way)? and How come request.getPathInfo() in service method returns null?

it should look like this:

String path = request.getRequestURI();     // /MyProject/MyServer/rpi//checktask?rpi="rpi"
String query = request.getQueryString();   // rpi="rpi"
String context = request.getContextPath(); // /MyProject
String servlet = request.getServletPath(); // /MyServer/rpi
String info = request.getPathInfo();       // /checktask?rpi="rpi"

What am I doing wrong?

Answer 1

Your URL string is

http://192.168.0.10:8080/MyProject/MyServer/rpi/checktask?rpi="rpi" 

The name of the parameter in the above String is "rpi".

The below code will give you the required value of the parameter "rpi".

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