PageRoutingServlet.java

public class PageRoutingServlet extends HttpServlet {

  private Map<String, PageController> pages = Maps.newHashMap();

  @Override
  public void init(ServletConfig config) throws ServletException {
    super.init(config);

    pages.put("/page1", new PageController() {
      @Override
      public void handle(Request request, Response response) throws IOException {
        PrintWriter writer = response.getWriter();
        writer.println("Page1 Page");
        writer.flush();
      }
    });

    pages.put("/page2", new PageController() {
      @Override
      public void handle(Request request, Response response) throws IOException {
        PrintWriter writer = response.getWriter();
        writer.println("Page2 Page");
        writer.flush();
      }
    });

    pages.put("/showInfo", new PageController() {
      @Override
      public void handle(Request request, Response response) throws IOException {
        PrintWriter writer = response.getWriter();
        writer.println("Info Page");
        writer.flush();
      }
    });
  }

  interface Request {

    String param(String key);

  }

  interface Response {

    PrintWriter getWriter() throws IOException;

  }

  interface PageController {
    void handle(Request request, Response response) throws IOException;
  }

  @Override
  protected void service(final HttpServletRequest req, final HttpServletResponse resp) throws ServletException, IOException {

    PageController pageController = pages.get(req.getRequestURI());

    if (pageController == null) {
      resp.sendError(HttpServletResponse.SC_NOT_FOUND);
      return;
    }

    pageController.handle(
            new Request() {
              @Override
              public String param(String key) {
                return req.getParameter(key);
              }
            },
            new Response() {
              @Override
              public PrintWriter getWriter() throws IOException {
                return resp.getWriter();
              }
            }
    );

  }
  
}

web.xml

  <servlet>
    <servlet-name>routingServlet</servlet-name>
    <servlet-class>com.clouway.http.PageRoutingServlet</servlet-class>
  </servlet>

  <servlet-mapping>
    <servlet-name>routingServlet</servlet-name>
    <url-pattern>/</url-pattern>
  </servlet-mapping>