MirrorServlet.java

package servlets;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

/**
 * @author v.chibrikov
 */
public class MirrorServlet extends HttpServlet {

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

        String value = request.getParameter("key");
        if (value != null)
            response.getWriter().println(value);

        response.setContentType("text/html;charset=utf-8");
        response.setStatus(HttpServletResponse.SC_OK);

    }
}