Metacat

/**

 *   '$Author: jones $'

 *     '$Date: 2001-07-20 11:23:06 -0700 (Fri, 20 Jul 2001) $'

 * '$Revision: 800 $'

 *

 * 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.net.*;

public class RelationHandler //implements Runnable

{

  private Thread btThread = null;

  private Connection conn = null;

  private String docid = 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 docid the ID of the XML document to index.

   */

  public RelationHandler(String docid, Connection conn)

  {

    this.conn = conn;

    this.docid = docid;

    putRelations();

  }

  /**

   * insert the relations specified in the triples into xml_relation table

   */ 

  public void putRelations() {

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

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

      DocumentImpl xmldoc = new DocumentImpl(conn,docid,false);

      //DocumentImpl xmldoc = new DocumentImpl(conn);

      //xmldoc.getDocumentInfo(docid);

      String packagetype = xmldoc.getDoctype();

      // first delete the relations for this package document if any

      deleteRelations(docid);

      // put the new relations

      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);

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

        pstmt.execute(); 

        hasmorerows = rs.next();

      }

      pstmt.close();

      conn.commit();

    } catch(Exception e) { 

      MetaCatUtil.debugMessage("Error in RelationHandler.run(): " + 

                               e.getMessage());

      System.out.println("Error in RelationHandler.run(): " + 

                               e.getMessage());

      try { 

        conn.rollback();

      } catch (SQLException sqle) {

        System.out.println("Error in RelationHandler.run(): " + 

                           sqle.getMessage());

      }

    }

  }

  /**

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

   * @param docid the docid to delete.

   */

  public void deleteRelations(String docid) throws SQLException

  {

    try {

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

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

      pstmt.execute();

      pstmt.close();

    } catch(SQLException e) {

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

                          e.getMessage());

      System.out.println("error in RelationHandler.deleteRelations(): " + 

                          e.getMessage());

      throw e;

    }

  }

}