Metacat

    <UserLayer>

    <Name>metacat:data_bounds</Name>

    </UserLayer>

        <UserLayer>

        <Name>metacat:data_points</Name>

        </UserLayer>

/**

 *  '$RCSfile$'

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

 *  National Center for Ecological Analysis and Synthesis

 *

 *  Author: Matthew Perry

 *  '$Date$'

 *  '$Revision$'

 *

 *  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

import edu.ucsb.nceas.metacat.MetaCatUtil;

import java.io.FileNotFoundException;

import java.util.Vector;

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

    String filename = MetaCatUtil.getOption("certPath") + "data/styles/" + dataset;

    try {

	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();

    }

   * The sld file is specified without path and 

   * must exist within geoserver's styles folder (context/data/styles/*)

  private String getSld(String filename) throws FileNotFoundException

	    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 = "";

		    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);

	    } 

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

  private Element getFilterElement(Document inDoc, Vector docids) 

	  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);

   <p style="margin-bottom:12pt">Closely related to the WMS bypass implemetation, the SLD factory would be in charge of constructing the filter based on on the contraints mentioned above. In other words, it would construct a document specifying which docids were to appear in the map. Because it would have to generate this list of docids on every wms request, performance is a big concern. Likely we'll need to cache docid lists as session variables.</p>

  <p> There is currently a stub implementation of the SLD Factory servlet in <em>src/edu/ucsb/nceas/metacat/spatial/SldFactory.java</em>. It is functional except that it doesn't generate a dynamic list of allowable docids.  Assuming we can modify the SldFactory servlet to quickly generate a list of allowable docids based on stored session variables, applying this SLD to a WMS request is fairly easy and simply requires appending the URL of the sldfactory as an "SLD" parameter to the WMS GetMap request: </p>

   <pre> http://indus/knb/wms?REQUEST=GetMap&SERVICE=WMS....&SLD=http://indus.msi.ucsb.edu/knb/sldfactory?originalSld=data_points_style.sld</pre>

<p> where data_points_style.sld is the original style document existing in <em>{context}/data/styles/</em>. The sldfactory servlet will construct a list of allowable docids, append those to the original sld as an ogc filter, an return a (modified) SLD document. There are two possibilities for implementing this:</p>

   <ol>

   <li>

     Mapbuilder (the WMS client in charge of constructing WMS request) can be told to append this SLD parameter through the use of the WMC config document. This would work for the skins but, alone, would not ensure that every WMS request were filtered since other clients could simply ommit the SLD parameter.

   </li>

   <li> 

     An alternative, one that would ensure that EVERY wms request was filtered, would be to handle it all server side with a WMS bypass.

   </li>

   </ol>