Metacat

/**

 *   '$Author: jones $'

 *     '$Date: 2001-05-21 13:51:10 -0700 (Mon, 21 May 2001) $'

 * '$Revision: 743 $'

 *

 * 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

 */

package edu.ucsb.nceas.metacat;

import java.sql.*;

import java.util.*;

import java.lang.Thread; 

import java.net.*;

public class RelationHandler implements Runnable

{

  private Thread btThread = null;

  private Connection conn = null;

  private DocumentImpl xmldoc = null;

  MetaCatUtil util = new MetaCatUtil();

  /** 

   * Constructor for this class.  finds all of the relations to a single xml

   * document and writes them to the database.  This includes transitive

   * relations.

   * @param xmldoc the xml document to index.

   */

  public RelationHandler(DocumentImpl xmldoc, Connection conn)

  {

    //this.conn = conn;

    try

    {

      conn = MetacatReplication.getDBConnection("RelationHandler." +

                                                "relationHandler");

    }

    catch(Exception e)

    {

      MetaCatUtil.debugMessage("unable to get db connection in " + 

                         "relationhandler: " + e.getMessage());

    }

    this.xmldoc = xmldoc;

    if(xmldoc.getDoctype().equals(util.getOption("packagedoctype")))

    { //make sure this doctype is a package document then run the thread

      btThread = new Thread(this);

      btThread.setPriority(Thread.MIN_PRIORITY);

      btThread.start();

    }

  }

  /**

   * The thread handler

   */ 

  public void run()

  {

    MetaCatUtil.debugMessage("Running relation handler!");

    Connection dbconn = null;

    String docid = xmldoc.getDocID();

    String packagetype = xmldoc.getDoctype();

    // deletes all of the relations with a docid of @docid.

    deleteRelations(docid);

    //pseudo-code algorithm

    //for each new relation r in xml_nodes

    //  put r into xml_relation

    //  compare r to each relation already in xml_relation

    //  if r isrelatedto a row in xml_relation

    //    add a new row to xml_relation that represents this new relation

    try

    {

      dbconn = MetacatReplication.getDBConnection("RelationHandler." +

                                                  "run");

      PreparedStatement pstmt = dbconn.prepareStatement(

                                QuerySpecification.printPackageSQL(docid));

      pstmt.execute();

      //get the new relations out of xml_nodes

      ResultSet rs = pstmt.getResultSet();

      boolean hasmorerows = rs.next();

      while(hasmorerows)

      {

        String subject = rs.getString(1);

        String relationship = rs.getString(2);

        String object = rs.getString(3);

        String subjectDoctype = null;

        String paramDocid = null;

        URL subjectMurl = null;

        //get the current relations information

        String subDocid = null;

        String objDocid = null;

        String subDoctype = null;

        String objDoctype = null;

        try

        {

          URL subMurl = new URL(subject);

          if(subMurl.getQuery() != null)

          {

            Hashtable subMurlParams = util.parseQuery(subMurl.getQuery());

            subDocid = (String)subMurlParams.get("docid");

            if(subMurl.getProtocol().equals("metacat"))

            {

              DocumentImpl subDoc = new DocumentImpl(dbconn, subDocid);

              subDoctype = subDoc.getDoctype();

            }

          }

          else

          {

            subDocid = subject;

          }

        }

        catch(MalformedURLException murle)

        { //assume this is just a docid not a url

          subDocid = subject;

        }

        try

        {

          URL objMurl = new URL(object); 

          if(objMurl.getQuery() != null)

          {

            Hashtable objMurlParams = util.parseQuery(objMurl.getQuery());

            objDocid = (String)objMurlParams.get("docid");

            if(objMurl.getProtocol().equals("metacat"))

            {

              DocumentImpl objDoc = new DocumentImpl(dbconn, objDocid);

              objDoctype = objDoc.getDoctype();

            }

          }

          else

          {

            objDocid = object;

          }

        }

        catch(MalformedURLException murle)

        { //assume this is just a docid

          objDocid = object;

        }

        //now that the comparisons are done, the new relation can be put

        //into xml_relation

        StringBuffer insertStmt = new StringBuffer();

        insertStmt.append("insert into xml_relation (docid, packagetype, ");

        insertStmt.append("subject, subdoctype, ");

        insertStmt.append("relationship, object, objdoctype) values ('");

        insertStmt.append(docid).append("', '");

        insertStmt.append(packagetype).append("', '");

        insertStmt.append(subject).append("', '");

        insertStmt.append(subDoctype).append("', '");

        insertStmt.append(relationship).append("', '");

        insertStmt.append(object).append("', '");

        insertStmt.append(objDoctype).append("')");

        pstmt = dbconn.prepareStatement(insertStmt.toString());

        pstmt.execute(); 

        hasmorerows = rs.next();

      }

      dbconn.commit();

      pstmt.close();

      dbconn.close();

      btThread = null;

    } 

    catch(Exception e) 

    { 

      MetaCatUtil.debugMessage("Error in relationHandler.run: " + 

                               e.getMessage());

      btThread = null;

      try 

      { 

        conn.rollback();

      } 

      catch (SQLException sqle) {}

    }

  }

  /**

   * Deletes all of the relations with a docid of 'docid'.

   * @param docid the docid to delete.

   */

  public void deleteRelations(String docid)

  {

    Connection dbconn = null;

    try

    {

      dbconn = MetacatReplication.getDBConnection("RelationHandler."+

                                                  "deleteRelations");

    }

    catch(Exception ee)

    {

      MetaCatUtil.debugMessage("error in relationHandler.deleteRelations: " +

                          ee.getMessage());

    }

    try

    {

      PreparedStatement pstmt = dbconn.prepareStatement("delete from " +

                             "xml_relation where docid like '" + docid + "'");

      pstmt.execute();

      pstmt.close();

      dbconn.close();

    }

    catch(Exception e)

    {

      MetaCatUtil.debugMessage("error in RelationHandler.deleteRelations(): " + 

                          e.getMessage());

      try 

      { 

        dbconn.rollback();

        dbconn.close();

      } 

      catch (SQLException sqle) {}

    }

  }

}