Java servlet throw http 500 error on purpose

I am developing a java servlet. I am using glassfish server 4.

End users are sending me information through URL parametars, something like this:

http://myIP:8080/TestProject/TestServlet?param1=test1&param2=test2&param3=test3

I am getting the values from param1, param2 and param3 and i want to write them in my database. If I get a SQL exception while writing the informations in my db i want to throw "500 Internal Server Error" to let them know that i have some technical problems and to resend their request. I want to know is there a default way to do this, set some status, display text ...?

Here is the code:

@WebServlet(urlPatterns = {"/TestServlet"}, initParams = {
    @WebInitParam(name = "param1", value = ""),
    @WebInitParam(name = "param2", value = ""),
    @WebInitParam(name = "param3", value = "")})
public class TestServlet extends HttpServlet {

    String param1;
    String param2;
    String param3;
    boolean dbOK;

    /**
     * Processes requests for both HTTP
     * <code>GET</code> and
     * <code>POST</code> methods.
     *
     * @param request servlet request
     * @param response servlet response
     * @throws ServletException if a servlet-specific error occurs
     * @throws IOException if an I/O error occurs
     */
    protected void processRequest(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        //Get parametars from the request
        param1 = request.getParameter("param1");
        param2 = request.getParameter("param2");
        param3 = request.getParameter("param3");
        //Input in db
        dbOK = Database.saveParams(param1,param2,param3);

        //Print response
        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out = response.getWriter();
        try {
            /* TODO output your page here. You may use following sample code. */
            out.println("<!DOCTYPE html>");
            out.println("<html>");
            out.println("<head>");
            out.println("<title>T-Mobile Interface</title>");            
            out.println("</head>");
            out.println("<body>");
            out.println("<h1> dbOK=" + dbOK + "</h1>");
            out.println("</body>");
            out.println("</html>");
        } finally {            
            out.close();
        }
    }

    // <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code.">
    /**
     * Handles the HTTP
     * <code>GET</code> method.
     *
     * @param request servlet request
     * @param response servlet response
     * @throws ServletException if a servlet-specific error occurs
     * @throws IOException if an I/O error occurs
     */
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        processRequest(request, response);
    }

    /**
     * Handles the HTTP
     * <code>POST</code> method.
     *
     * @param request servlet request
     * @param response servlet response
     * @throws ServletException if a servlet-specific error occurs
     * @throws IOException if an I/O error occurs
     */
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        processRequest(request, response);
    }

    /**
     * Returns a short description of the servlet.
     *
     * @return a String containing servlet description
     */
    @Override
    public String getServletInfo() {
        return "Short description";
    }// </editor-fold>
}

Solution

You should be able to do that with response.sendError(int)

EDIT: Was meant to say that the parameter is the error code you want to send, so in your case 500.