Metacat

/*

 * Styled Layer Descriptor Factory

 * Author: Matt Perry

 * Status: testing

 * MPTODO: Use a spatial access constraints class to generate the appropriate SLD filter

 */

package edu.ucsb.nceas.metacat.spatial;

import edu.ucsb.nceas.utilities.XMLUtilities;

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 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.

   * @todo Determine filename from variables in metacat.properties.

   */

  private void handleGetOrPost(HttpServletRequest request, HttpServletResponse response)

  throws ServletException, IOException

  {

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

    // MPTODO : Eventually use dataset to determine filename

    String filename = "/var/lib/tomcat5/webapps/knb/style/skins/ebm/spatial/data_bounds_style.sld";

    String sld = getSld(filename);

    response.setContentType("text/xml");

    response.getWriter().write(sld);

    System.out.println("\n*** SldFactory request handled ***\n");

  }

  /**

   * 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. 

   * 

   * 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)

  {

	    DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();

	    try {

	       DocumentBuilder builder = factory.newDocumentBuilder();

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

	    } catch (SAXException sxe) {

	       sxe.printStackTrace();

	    } catch (ParserConfigurationException pce) {

	       pce.printStackTrace();

	    } catch (IOException ioe) {

	       ioe.printStackTrace();

	    }

	    Element root = document.getDocumentElement();

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

	    Node ruleNode = elemList.item(0);

	    // Get the list of docids  due to access contrainsts

	    // Get the list of docids  due to skin filtering of org names

	    // Get the list of docids  due to existing query (eg taxonomic)

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

	    Element filterElement = getFilterElement(document);

	    // Append the Filter to the ruleNode

	    ruleNode.appendChild(filterElement);

	    // Write new DOM as a string

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

	    return rulesString;

  }

  /**

   * Given a DOM document and a vector of docids,

   * Creates an OGC Filter node

   * 

   * @param inDoc	DOM document.

   * 

   */

  private Element getFilterElement(Document inDoc) 

  {

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

	  // MPTODO : BEGIN LOOP thru vector of docids

	  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");	  

	  Text literalText = inDoc.createTextNode("perry.1"); // i

	  literalElem.appendChild(literalText);

	  opElem.appendChild(propertyElem);

	  opElem.appendChild(literalElem);

	  filterElem.appendChild(opElem);

	  // END LOOP

	  return filterElem;	  

  }

}