naviservlet.java

mapxtreme for java 的开发实例

      {
        // initialize client's map-state and create servlet session
        createNewClientSession(req);
      }

      //------------------------------------------------------------------------
      // obtain the client MAPJ object from servlet session
      //------------------------------------------------------------------------
      if ((clientSession = req.getSession(false)) == null)
      {
        throw new ServletException("CLIENT SESSION NOT OBTAINED.");
      }
      else if ((mapj=(MapJ)clientSession.getAttribute(NaviServlet.m_sessionNameForMapJ)) == null)
      {
        throw new ServletException("MAPJ NOT OBTAINED FROM SESSION.");
      }

      //------------------------------------------------------------------------
      // handle ZOOM-IN / ZOOM-OUT / PAN request
      //------------------------------------------------------------------------
      if (httpParam_requestType != null)
      {
        //----------------------------------------------------------------------
        // in all cases we apply a PAN operation
        //----------------------------------------------------------------------
        DoublePoint dp = mapj.transformScreenToNumeric
        (
          new DoublePoint
          (
            Double.parseDouble(httpParam_clickX),
            Double.parseDouble(httpParam_clickY)
          )
        );
        mapj.setCenter(dp);

        //----------------------------------------------------------------------
        // if we need to further ZOOM-IN
        //----------------------------------------------------------------------
        if (httpParam_requestType.equalsIgnoreCase(NaviServlet.m_requestZoomIn))
        {
          mapj.setZoom(mapj.getZoom()/2);
        }

        //----------------------------------------------------------------------
        // if we need to further ZOOM-OUt
        //----------------------------------------------------------------------
        else if (httpParam_requestType.equalsIgnoreCase(NaviServlet.m_requestZoomOut))
        {
          mapj.setZoom(mapj.getZoom()*2);
        }
      }

      //------------------------------------------------------------------------
      // now that the map-state has been setup / modified according to the
      // client request type, we need to formulate our response and send it
      // back to the client.
      //------------------------------------------------------------------------

      // create a GIF image of the map in a web-accessable directory
      String mapImageFilename = createNextMapImage(mapj);

      System.out.println("");
      System.out.println("mapImageFilename ["+mapImageFilename+"]");

      // create IMAGE URL that client will use to get image
      String protocol = req.getScheme();
      String serverName = req.getServerName();
      String serverPort = String.valueOf(req.getServerPort());
      String contextPath = req.getContextPath();

      System.out.println("");
      System.out.println("protocol    ["+protocol+"]");
      System.out.println("serverName  ["+serverName+"]");
      System.out.println("serverPort  ["+serverPort+"]");
      System.out.println("contextPath ["+contextPath+"]");

      String imageURL =
      protocol+"://"+serverName+":"+serverPort+contextPath+"/images/"+mapImageFilename+"?refresh="+Math.random();

      System.out.println("");
      System.out.println("imageURL    ["+imageURL+"]");

      // create server URL that client will contact in subsequent request
      System.out.println("URL before sessionID: ["+req.getRequestURL()+"]");
      String thisServletURL = resp.encodeURL(req.getRequestURL().toString());
      System.out.println("URL after sessionID: ["+thisServletURL+"]");

      // create return HTML for return to client
      System.out.println("createResponseHtml");

      // maintain button selected state between requests
      String panChecked = "Checked";
      String zoomInChecked = "";
      String zoomOutChecked = "";

      if (httpParam_requestType != null) // can happen on init request
      {
        if (httpParam_requestType.equalsIgnoreCase(NaviServlet.m_requestZoomIn))
        {
          zoomInChecked = "checked";
        }
        else if (httpParam_requestType.equalsIgnoreCase(NaviServlet.m_requestZoomOut))
        {
          zoomOutChecked = "checked";
        }
        else
        {
          panChecked = "checked";
        }
      }

      resp.setContentType("text/html");
      PrintWriter toClient = resp.getWriter();

      toClient.println("<form action\""+thisServletURL+"\"= method=\"post\">");
      toClient.println("<center>");
      toClient.println("<h2>NAVI</h2>");
      toClient.println("<hr>");
      toClient.println("<table border=1>");
      toClient.println("<tr><td>");
      toClient.println("<input type=\"image\" name=\"map\" src=\""+imageURL+"\" alt=\"map image\" border=1/>");
      toClient.println("</td></tr>");
      toClient.println("</table>");
      toClient.println("</center>");
      toClient.println("<br/><br/>");
      toClient.println("<center>");
      toClient.println("<input type=\"radio\" name=\"action\" value=\"pan\""  +panChecked+">Pan</input>");
      toClient.println("<input type=\"radio\" name=\"action\" value=\"zin\""  +zoomInChecked+">ZoomIn</input>");
      toClient.println("<input type=\"radio\" name=\"action\" value=\"zout\"" +zoomOutChecked+">ZoomOut</input>");
      toClient.println("</center>");
      toClient.println("</form>");
      toClient.println("<center>");
      toClient.println("<table border=1>");
      toClient.println("<tr>");
      toClient.println("<td><b>MDF:</b></td><td>"+NaviServlet.m_mdfFileToLoad+"</td>");
      toClient.println("</tr>");
      toClient.println("<tr>");
      toClient.println("<td><b>ZOOM:</b></td><td>"+mapj.getZoom()+"</td>");
      toClient.println("</tr>");
      toClient.println("</table>");
      toClient.println("</center>");

    }
    catch(Exception e)
    {
      System.out.println("MAJOR EXCEPTION - RESPONSE *NOT* SENT BACK TO CLIENT.");
      System.out.println("EXCEPTION: ["+e.getMessage()+"]");
      e.printStackTrace();
    }
  }

  /**
   * creates a new servlet session for the connecting client, and throws an
   * exception if a session cannot be created.
   *
   * @param req an HttpServletRequest object that contains the request the
   *        client has made of the servlet
   * @throw ServletException if the map image could not be created.
   */
  private void createNewClientSession(HttpServletRequest req)
  throws ServletException
  {
    // create a new session for the client and throw exception if NOT created
    HttpSession session = null;
    if ((session = req.getSession())==null)
    {
      throw new ServletException("CANNOT CREATE NEW CLIENT SESSION");
    }
    else
    {
      try
      {
        // once the session has been created, we must create an instance of the
        // mapj object to hold our client's map-state.  Once initialized, we will
        // store the MapJ object to session for subsequent use by the client.
        MapJ mapj = new MapJ();
        mapj.setDeviceBounds(new DoubleRect(0,0,320,200));
        System.out.println("MapJ object created.");
        mapj.loadMapDefinition(NaviServlet.m_mdfFileToLoad);
        System.out.println("MDF file ["+NaviServlet.m_mdfFileToLoad+"] loaded.");
        session.setAttribute(NaviServlet.m_sessionNameForMapJ, mapj);
        System.out.println("MapJ object stored to session.");
      }
      catch(Exception e)
      {
        throw new ServletException(e.getMessage());
      }
    }
  }

  /**
   * generates a new map image for the current client.
   *
   * @param mapj map-state of current client.
   * @throw ServletException if problem occurs during image creation.
   * @return the filename of the GIF file that was created.
   */
  synchronized private String createNextMapImage(MapJ mapj) throws ServletException
  {
    String returnValue = null;

    try
    {
      System.out.println("attempting to generate map image GIF file...");

      ImageRequestComposer irc =
      ImageRequestComposer.create
      (
        mapj,
        ImageRequestComposer.MAX_COLORS_TRUECOLOR,
        Color.blue,
        "image/gif"
      );

      MapXtremeImageRenderer mir =
      new MapXtremeImageRenderer(NaviServlet.m_urlOfMapXtremeServlet);
      mir.render(irc);

      returnValue = "map"+(NaviServlet.sequenceNumber++)+".gif";
      mir.toFile(NaviServlet.m_imageDirectory+"/"+returnValue);
      System.out.println("GIF file ["+NaviServlet.m_imageDirectory+
      "/"+returnValue+"] created.");
    }
    catch(Exception e)
    {
      throw new ServletException(e.getMessage());
    }

    return returnValue;
  }
}
// eof