Package squirrelrdf

Source Code of squirrelrdf.Servlet

/*
* (c) Copyright 2006 Hewlett-Packard Development Company, LP
* All rights reserved.
* [See end of file]
*/

package squirrelrdf;

import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import com.hp.hpl.jena.query.DatasetFactory;
import com.hp.hpl.jena.query.Query;
import com.hp.hpl.jena.query.QueryFactory;
import com.hp.hpl.jena.query.ResultSet;
import com.hp.hpl.jena.query.ResultSetFormatter;
import com.hp.hpl.jena.query.engine1.QueryEngine;
import com.hp.hpl.jena.rdf.model.Model;
import com.hp.hpl.jena.util.FileManager;
import com.hp.hpl.jena.vocabulary.RDF;
import com.hp.hpl.squirrelrdf.ldap.LdapMap;
import com.hp.hpl.squirrelrdf.ldap.LdapQueryEngine;
import com.hp.hpl.squirrelrdf.rdb.DbMap;
import com.hp.hpl.squirrelrdf.rdb.SQLQueryEngine;

/**
* A very simple servlet
*
* @author pldms
*
*/
public class Servlet extends HttpServlet
{
  private static final long serialVersionUID = -5436891956454723505L;

  final static Log log = LogFactory.getLog(Servlet.class);

  final static int NONE = 0;

  final static int RDB = 1;

  final static int LDAP = 2;

  Model config;

  int type;

  public void init()
  {
    String configFile = this.getInitParameter("config");

    log.info("Config file: " + configFile);

    config = FileManager.get().loadModel(
        this.getServletContext().getRealPath(configFile));

    if (config.contains(null, RDF.type, DbMap.Map))
      type = RDB;
    else if (config.contains(null, RDF.type, LdapMap.Map))
      type = LDAP;
    else
    {
      type = NONE;
      throw new RuntimeException("Unknown configuration type");
    }
  }

  public void doGet(HttpServletRequest req, HttpServletResponse resp)
  {
    doQuery(req, resp);
  }

  public void doPost(HttpServletRequest req, HttpServletResponse resp)
  {
    doQuery(req, resp);
  }

  public void doQuery(HttpServletRequest req, HttpServletResponse resp)
  {
    QueryEngine qe = null;

    try
    {
      String theQuery = req.getParameter("query");
      String stylesheet = tryParameter(req, "stylesheet", "xsl", "xslt",
          "xslt-uri");

      log.info("Query is:\n" + theQuery);
      log.info("Stylesheet: " + stylesheet);

      Query query = QueryFactory.create(theQuery);

      if (type == LDAP)
        qe = new LdapQueryEngine(query, config);
      else
        qe = new SQLQueryEngine(query, config);

      qe.setDataset(DatasetFactory.create());

      ResultSet results = qe.execSelect();
      resp.setHeader("Content-Type", "application/xml");
      ResultSetFormatter.outputAsXML(resp.getOutputStream(), results,
          stylesheet);
    }
    catch (Throwable e)
    {
      log.error("Error: ", e);
      resp.setStatus(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
    }
    finally
    {
      if (qe != null)
        qe.close();
    }

  }

  /**
   * Try to get a parameter with a variety of names
   *
   * @param req
   * @param names
   * @return null if not found, otherwise parameter value
   */
  private String tryParameter(HttpServletRequest req, String... names)
  {
    for (String name : names)
    {
      if (req.getParameter(name) != null)
        return req.getParameter(name);
    }
    return null;
  }
}

/*
* (c) Copyright 2006 Hewlett-Packard Development Company, LP
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
*    notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
*    notice, this list of conditions and the following disclaimer in the
*    documentation and/or other materials provided with the distribution.
* 3. The name of the author may not be used to endorse or promote products
*    derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/ 
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