naviservlet.java

mapxtreme for java 的开发实例

package mxtj45;

////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////
// declare imports
////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////

// J2SE 1.3.1 imports
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Enumeration;

// J2EE 1.3.1 imports
import javax.servlet.*;
import javax.servlet.http.*;

// mxtj45. imports
import java.awt.*;
import com.mapinfo.mapj.*;
import com.mapinfo.mapxtreme.client.*;
import com.mapinfo.util.*;
import com.mapinfo.xmlprot.mxtj.*;

////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////
// top-level public class
////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////
/**
 * simple servlet that performs zoom / pan operations on an MDF file defined
 * map, such that all map images are stored on the webserver as GIF files in a
 * publicly accessible context directory, and client state is maintained in
 * a servlet session with session ID values being conveyed via URL rewriting.
 *
 * @author John Dove, MapInfo Technical Support Department, 2002
 */
public class NaviServlet extends HttpServlet
{
  //////////////////////////////////////////////////////////////////////////////
  //////////////////////////////////////////////////////////////////////////////
  // fields
  //////////////////////////////////////////////////////////////////////////////
  //////////////////////////////////////////////////////////////////////////////

  //----------------------------------------------------------------------------
  // static fields loaded as servlet initialization parameters
  //----------------------------------------------------------------------------

  /**
   * absolute path of MDF file to load into all MapJ object.
   */
  // REQUIRED IN WEB.XML
  static private String m_mdfFileToLoad;

  /**
   * url of the MapXtremeJava 4.5 servlet that is used for remote rendering.
   */
  // REQUIRED IN WEB.XML
  static private String m_urlOfMapXtremeServlet;

  /**
   * directory to create GIF files in on webserver machine.  These GIF images
   * will be referred to by URL links within the HTML documents returned to
   * clients.
   */
  // REQUIRED IN WEB.XML
  static private String m_imageDirectory;

  /**
   * flag that indicates if all the servlet initialization parameters were
   * loaded upon servlet startup.
   */
  static boolean m_allInitParamsLoaded;

  //----------------------------------------------------------------------------
  // names of HTTP parameters that can be sent by client
  //----------------------------------------------------------------------------

  /**
   * identifier for the http param that denotes the "type" of request sent by
   * a client.
   */
  static private String m_param_requestType = "action";

  /**
   * holds X-axis value of mouse click made by client on the map.
   */
  static private String m_param_screenClickX = "map.x";

  /**
   * holds Y-axis value of mouse click made by client on the map.
   */
  static private String m_param_screenClickY = "map.y";

  /**
   * http param value that denotes zoom-in operation.
   */
  static private String m_requestZoomIn = "zin";

  /**
   * http param value that denotes zoom-out operation.
   */
  static private String m_requestZoomOut = "zout";

  /**
   * http param value that denotes pan operation.
   */
  static private String m_requestPan = "pan";


  //----------------------------------------------------------------------------
  // static fields with names for session stored objects
  //----------------------------------------------------------------------------
  /**
   * name assigned to MapJ object when stored to session.
   */
  static private String m_sessionNameForMapJ = "mapj";

  /**
   * will be accessed via a synchronized code block to provide unique
   * incrementing long values on a per client-request basis
   */
  static private long sequenceNumber;  // defaults to zero

  //////////////////////////////////////////////////////////////////////////////
  //////////////////////////////////////////////////////////////////////////////
  // methods
  //////////////////////////////////////////////////////////////////////////////
  //////////////////////////////////////////////////////////////////////////////
  public void init() throws ServletException
  {
    System.out.println("NAVI SERVLET INITIALIZING...");

    // assume that all initialization parameters will NOT be loaded
    NaviServlet.m_allInitParamsLoaded = false;

    //--------------------------------------------------------------------------
    // read the following initialization parameters, which should all be defined
    // in the deployment descriptor (web.xml) file of the web application that
    // this servlet is a part of.
    //
    // 1. mdfFileToLoad
    // 2. urlOfMapXtremeServlet
    //
    // if any of these parameters are NOT obtained, we will throw an exception.
    //--------------------------------------------------------------------------
    m_mdfFileToLoad = this.getInitParameter("mdfFileToLoad");
    m_urlOfMapXtremeServlet = this.getInitParameter("urlOfMapXtremeServlet");
    m_imageDirectory = this.getInitParameter("imageDirectory");

    System.out.println("");
    System.out.println("SERVLET INIT PARAMETERS:");
    System.out.println("  mdfFileToLoad = ["+m_mdfFileToLoad+"]");
    System.out.println("  urlOfMapXtremeServlet = ["+m_urlOfMapXtremeServlet+"]");
    System.out.println("  imageDirectory = ["+m_imageDirectory+"]");
    System.out.println("");

    if (m_mdfFileToLoad == null)
    {
      throw new ServletException("init param [mdfFileToLoad] was null.");
    }
    else if (m_urlOfMapXtremeServlet == null)
    {
      throw new ServletException("init param [urlOfMapXtremeServlet] was null.");
    }
    else if (m_imageDirectory == null)
    {
      throw new ServletException("init param [imageDirectory] was null.");
    }

    // if we made it here, it means all the needed init params were obtained
    NaviServlet.m_allInitParamsLoaded = true;
  }

  /**
   * handles HTTP GET requests.  This method will execute in a separate thread
   * within the servlet container's JVM.
   *
   * @param req an HttpServletRequest object that contains the request the
   *        client has made of the servlet
   * @param resp an HttpServletResponse object that contains the response the
   *        servlet sends to the client
   * @throw java.io.IOException if an input or output error is detected when
   *        the servlet handles the GET request
   * @throw ServletException if the request for the GET could not be handled
   *
   */
  protected void doGet(HttpServletRequest req, HttpServletResponse resp)
  throws ServletException,java.io.IOException
  {
    this.doPost(req,resp);
  }

  /**
   * handles HTTP POST requests.  This method will execute in a separate thread
   * within the servlet container's JVM.
   *
   * @param req an HttpServletRequest object that contains the request the
   *        client has made of the servlet
   * @param resp an HttpServletResponse object that contains the response the
   *        servlet sends to the client
   * @throw java.io.IOException if an input or output error is detected when
   *        the servlet handles the request
   * @throw ServletException - if the request for the POST could not be handled
   */
  protected void doPost(HttpServletRequest req,HttpServletResponse resp)
  throws ServletException,java.io.IOException
  {
    String httpParam_requestType = null;  // http param sent by client
    String httpParam_clickX = null;       // http param sent by client
    String httpParam_clickY = null;       // http param sent by client
    HttpSession clientSession = null;     // client's session object
    MapJ mapj = null;                     // client's map-state object


    try
    {
      // throw exception if NOT all servlet init params were loaded on startup.
      // since this is the case, NO response will be sent back to the client.
      if (!NaviServlet.m_allInitParamsLoaded)
      {
        throw new ServletException("SOME SERVLET INIT PARAMS ARE MISSING.");
      }

      // read http parameters sent by client
      httpParam_requestType = req.getParameter(NaviServlet.m_param_requestType);
      httpParam_clickX = req.getParameter(NaviServlet.m_param_screenClickX);
      httpParam_clickY = req.getParameter(NaviServlet.m_param_screenClickY);

      //------------------------------------------------------------------------
      // if NO request type http param was sent, we will assume this is the
      // client's FIRST request to this servlet
      //------------------------------------------------------------------------
      if (httpParam_requestType == null)