Metacat

/**

 *  '$RCSfile$'

 *  Copyright: 2000 Regents of the University of California and the

 *  National Center for Ecological Analysis and Synthesis

 *

 *  Author: Matthew Perry

 *  '$Date: 2008-07-28 16:07:10 -0700 (Mon, 28 Jul 2008) $'

 *  '$Revision: 4167 $'

 *

 *  This program is free software; you can redistribute it and/or modify

 *  it under the terms of the GNU General Public License as published by

 *  the Free Software Foundation; either version 2 of the License, or

 *  (at your option) any later version.

 *  

 *  This program is distributed in the hope that it will be useful,

 *  but WITHOUT ANY WARRANTY; without even the implied warranty of

 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 *  GNU General Public License for more details.

 *

 *  You should have received a copy of the GNU General Public License

 *  along with this program; if not, write to the Free Software

 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

 *

 *  Purpose: Servlet to generate a styled layer descriptor (SLD)

 *           with a filter to restrict features on

 *           a WMS map to given docids

 *

 *  Status: Currently this is just a working stub

 *          with some hardcoded values. Since this needs to be

 *          fired off on every map redraw, we'll need a way to make 

 *          the generation of docid list very efficient. 

 *

 *  Usage: Append the URL as an "SLD" to any WMS GetMap request

 *    ex: http://server/context/wms?...&SLD=http://server/context/sldfactory?originalSld=data_points_style

 */

package edu.ucsb.nceas.metacat.spatial;

import edu.ucsb.nceas.utilities.XMLUtilities;

import edu.ucsb.nceas.metacat.util.SystemUtil;

import javax.servlet.ServletConfig;

import javax.servlet.ServletContext;

import javax.servlet.ServletException;

import javax.servlet.ServletInputStream;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import javax.servlet.http.HttpSession;

import javax.servlet.http.HttpUtils;

import javax.servlet.ServletOutputStream;

import javax.xml.parsers.DocumentBuilder; 

import javax.xml.parsers.DocumentBuilderFactory;  

import javax.xml.parsers.FactoryConfigurationError;  

import javax.xml.parsers.ParserConfigurationException;

import org.xml.sax.SAXException;  

import org.xml.sax.SAXParseException;

import java.io.File;

import java.io.IOException;

import java.io.FileNotFoundException;

import java.util.Vector;

import org.w3c.dom.*;

/**

 * Class to generate Styled Layer Descriptors allowing geoserver to 

 * filter the feature rendering based on various contraints 

 * such as permissions, non-spatial queries and skin configuration.

 */

public class SldFactory extends HttpServlet {

  static Document document;

  static String sld;

  /** 

   * Handle "GET" method requests from HTTP clients 

   *

   * @param request Incoming servlet request.

   * @param response Servlet response.

   */

  public void doGet(HttpServletRequest request, HttpServletResponse response)

  throws ServletException, IOException

  {

    handleGetOrPost(request, response);

  }

  /** 

   * Handle "POST" method requests from HTTP clients 

   *

   * @param request Incoming servlet request.

   * @param response Servlet response.

   */

  public void doPost(HttpServletRequest request, HttpServletResponse response)

  throws ServletException, IOException

  {

    handleGetOrPost(request, response);

  }

  /**

	 * Control servlet response depending on the action parameter specified

	 * Modifies the original SLD according to various access contraints and

	 * sends it as the servlet response.

	 * 

	 * @param request

	 *            Incoming servlet request.

	 * @param response

	 *            Servlet response.

	 */

	private void handleGetOrPost(HttpServletRequest request, HttpServletResponse response)

			throws ServletException, IOException {

		String dataset = request.getParameter("originalSld");

		try {

			String certPath = SystemUtil.getContextDir();

			String filename = certPath + "/data/styles/" + dataset;

			String sld = getSld(filename);

			System.out.println(sld);

			response.setContentType("text/xml");

			response.getWriter().write(sld);

		} catch (FileNotFoundException fnf) {

			fnf.printStackTrace();

		} catch (Exception e) {

			e.printStackTrace();

		}

	}

  /**

	 * Given a filename of an existing SLD document, reads the sld and adds an

	 * ogc:Filter to exclude/include certain docids based on user's permissions.

	 * The sld file is specified without path and must exist within geoserver's

	 * styles folder (context/data/styles/*)

	 * 

	 * returns SLD document as a String.

	 * 

	 * @param filename

	 *            Filename of the base sld.

	 * @todo Implement the doc id list queries for contraints.

	 */

  private String getSld(String filename) throws FileNotFoundException

  {

	    DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();

	    Vector allowedDocids = new Vector();

	    /*

	     * TODO : 

	     *  Get the list of allowable docids due to 

	     *    access contraints (based on current logged-in user)

	     *    skin filtering (eg organization name) 

	     *    existing non-spatial query (eg taxonomic query)

	     *

	     *  These could ideally be cached as session variables to improve

	     *  speed over running expensive SQL queries on 

	     *  each map redraw.

	     *

	     * Combined, these will be a vector of allowed docids that

	     * are to be displayed on the map

	     *

	     * Below is just a hardcoded example of the above...

	     *

	     */

	    allowedDocids.add("nceas.288");

	    allowedDocids.add("nrs.720");

	    String rulesString = "";

	    try {

		    DocumentBuilder builder = factory.newDocumentBuilder();

		    document = builder.parse( new File(filename) );	       

		    Element root = document.getDocumentElement();

		    NodeList elemList = document.getElementsByTagName("Rule");

		    Node ruleNode = elemList.item(0);

		    // Get the Element/node comprising the ogc:Filter for all of the above

		    Element filterElement = getFilterElement(document,allowedDocids);

		    // Append the Filter to the ruleNode

		    ruleNode.appendChild(filterElement);

		    // Write new DOM as a string

		    rulesString = XMLUtilities.getDOMTreeAsString((Node) root, true);

	    } catch (SAXException sxe) {

	       sxe.printStackTrace();

	    } catch (ParserConfigurationException pce) {

	       pce.printStackTrace();

	    } catch (IOException ioe) {

	       ioe.printStackTrace();

	    } 

	    return rulesString;

  }

  /**

   * Given a DOM document and a vector of docids,

   * Creates an OGC Filter node

   * 

   * @param inDoc	DOM document.

   * @param docids 	Vector of documents allowed in the map.

   */

  private Element getFilterElement(Document inDoc, Vector docids) 

  {

	  Element filterElem = inDoc.createElement("ogc:Filter");

	  Element orElem = inDoc.createElement("ogc:Or");

	  String docid = "";

	  // Begin loop thru vector of allowed docids

	  for (int i = 0; i < docids.size(); i++) {

		  Element opElem = inDoc.createElement("ogc:PropertyIsEqualTo");

		  Element propertyElem = inDoc.createElement("ogc:PropertyName");

		  Text propertyText = inDoc.createTextNode("docid");

		  propertyElem.appendChild(propertyText);

		  Element literalElem = inDoc.createElement("ogc:Literal");	  

		  docid = (String)docids.elementAt(i);

		  Text literalText = inDoc.createTextNode(docid); 

		  literalElem.appendChild(literalText);

		  opElem.appendChild(propertyElem);

		  opElem.appendChild(literalElem);

		  orElem.appendChild(opElem);

		  // END LOOP

	  }

	  filterElem.appendChild(orElem);

	  return filterElem;	  

  }

}