Metacat

/**

 *  '$RCSfile$'

 *    Purpose: A class to asyncronously build the package relation index

 *             in the database table xml_relation.

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

 *             National Center for Ecological Analysis and Synthesis

 *    Authors: Chad Berkley

 *    Release: @release@

 *

 *   '$Author$'

 *     '$Date$'

 * '$Revision$'

 */

package edu.ucsb.nceas.metacat;

import java.sql.*;

import java.util.*;

import java.lang.Thread;

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)

  {

    try

    {

      conn = util.getConnection();

    }

    catch(Exception e)

    {

      System.out.println("error getting db connection in relationhandler");

    }

    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()

  {

    //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

    {

      String docid = xmldoc.getDocID();

      PreparedStatement pstmt = conn.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);

        metacatURL subjectMurl = new metacatURL(subject);

        String subjectDoctype = null;

        if(subjectMurl.getURLType().equals("metacat"))

        {

          DocumentImpl subDoc = new DocumentImpl(conn, 

                                                 subjectMurl.getParam(0)[1]);

          subjectDoctype = subDoc.getDoctype();

        }

        String relationship = rs.getString(2);

        String object = rs.getString(3);

        //compare r to each relation in xml_relation

        pstmt = conn.prepareStatement("select subject, subdoctype, " +

                                      "relationship, object, objdoctype " +

                                      "from xml_relation");

        pstmt.execute();

        //get each relation in xml_relation for comparison

        ResultSet relations = pstmt.getResultSet();

        boolean hasmorerelations = relations.next();

        while(hasmorerelations)

        {

          String currentSub = relations.getString(1);

          String currentSubDoctype = relations.getString(2);

          String currentRelationship = relations.getString(3);

          String currentObj = relations.getString(4);

          String currentObjDoctype = relations.getString(5);

          if(object.equals(currentObj))

          {//there is a transitive relation so add a new relation to the table

            StringBuffer insertTransRelation = new StringBuffer();

            insertTransRelation.append("insert into xml_relation (subject, ");

            insertTransRelation.append("subdoctype, relationship, object, ");

            insertTransRelation.append("objdoctype) values ('");

            insertTransRelation.append(currentSub).append("', '");

            insertTransRelation.append(currentSubDoctype).append("', ");

            insertTransRelation.append("'hasTransitiveRelationTo', '");

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

            insertTransRelation.append(subjectDoctype).append("')");

            pstmt = conn.prepareStatement(insertTransRelation.toString());

            pstmt.execute();

            insertTransRelation = new StringBuffer();

            //put the same relation in with the subject and object switched

            insertTransRelation.append("insert into xml_relation (subject, ");

            insertTransRelation.append("subdoctype, relationship, object, ");

            insertTransRelation.append("objdoctype) values ('");

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

            insertTransRelation.append(subjectDoctype).append("', ");

            insertTransRelation.append("'hasTransitiveRelationTo', '");

            insertTransRelation.append(currentSub).append("', '");

            insertTransRelation.append(currentSubDoctype).append("')");

            pstmt = conn.prepareStatement(insertTransRelation.toString());

            pstmt.execute();

          }

          hasmorerelations = relations.next();

        }

        //get the current relations information

        metacatURL subMurl = new metacatURL(subject);

        metacatURL objMurl = new metacatURL(object);

        String subDoctype = null;

        String objDoctype = null;

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

        {

          DocumentImpl subDoc = new DocumentImpl(conn, subMurl.getParam(0)[1]);

          subDoctype = subDoc.getDoctype();

        }

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

        {

          DocumentImpl objDoc = new DocumentImpl(conn, objMurl.getParam(0)[1]);

          objDoc.getDoctype();

        }

        //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 (subject, subdoctype, ");

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

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

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

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

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

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

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

        pstmt.execute(); 

        hasmorerows = rs.next();

      }

      util.returnConnection(conn);

      btThread = null;

    }

    catch(Exception e)

    {

      System.out.println("Error in relationHandler: " + e.getMessage());

      util.debugMessage("Error in relationHandler: " + e.getMessage());

      btThread = null;

    }

  }

}