Metacat

/**

 *  '$RCSfile$'

 *    Purpose: An abstract class that encapsulates access to any RDBMS.

 *             This allows to swap easily between databases without any

 *             modification to the application.

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

 *             National Center for Ecological Analysis and Synthesis

 *    Authors: Jivka Bojilova

 *    Release: @release@

 *

 *   '$Author$'

 *     '$Date$'

 * '$Revision$'

 *

 * 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.dbadapter;

import java.sql.*;

import edu.ucsb.nceas.metacat.MetaCatUtil;

/**

 * Java offers uniform database access through the use of JDBC.

 * But many databases still use different SQL implementations and 

 * conventions. Thus this class offers extended programming interface

 * that all subclasses should implement to gain access to different

 * databases.

 *

 * To add a new database adapter class you must create a new class 

 * DB<dbname> that extends edu.ucsb.nceas.dbadapter.DBAdapter (where

 * dbname is the name of the database or database driver you wish to

 * add to your application). DBAdapter is an abstract class, thus the

 * subclasses need to implement the abstract methods.

 */

public abstract class DBAdapter {

  /**

   * Unique ID generator

   *

   * @param conn db connection in which to generate the unique id

   * @param tableName the table which unique id to generate

   * @exception SQLException <br/> any SQLException that can be thrown 

   *            during the db operation

   * @return return the generated unique id as a long type

   */

  public abstract long getUniqueID(Connection conn, String tableName) 

                                                  throws SQLException;

  /**

   * The function name that gets the current date and time

   * from the database server

   *

   * @return return the current date and time function name

   */

  public abstract String getDateString();

  /**

   * The character that the specific database implementation uses to 

   * indicate string literals in SQL. This will usually be a single

   * qoute (').

   *

   * @return return the string delimiter

   */

  public abstract String getStringDelimiter();

  /**

   * Instantiate a class using the name of the class at runtime

   *

   * @param className the fully qualified name of the class to instantiate

   */

  static public Object createObject(String className) throws Exception {

    Object object = null;

    try {

      Class classDefinition = Class.forName(className);

      object = classDefinition.newInstance();

    } catch (InstantiationException e) {

      throw e;

    } catch (IllegalAccessException e) {

      throw e;

    } catch (ClassNotFoundException e) {

      throw e;

    }

    return object;

  }

  /**

   * the main routine used to test the DBAdapter utility.

   */

  static public void main(String[] args) {

    // Determine our db adapter class and

    // create an instance of that class

    try {

      MetaCatUtil util = new MetaCatUtil();

      String dbAdapter = util.getOption("dbAdapter");

      DBAdapter dbAdapterObj = (DBAdapter)createObject(dbAdapter);

      // test if they work correctly

      String date = dbAdapterObj.getDateString();

      Connection conn = util.openDBConnection();

      long uniqueid = dbAdapterObj.getUniqueID(conn, "xml_catalog");

      conn.close();

      conn = null;

    } catch (Exception e) {

      System.out.println(e);

    }

  }

}

/**

 *  '$RCSfile$'

 *    Purpose: A db adapter class for Oracle RDBMS.

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

 *             National Center for Ecological Analysis and Synthesis

 *    Authors: Jivka Bojilova

 *    Release: @release@

 *

 *   '$Author$'

 *     '$Date$'

 * '$Revision$'

 *

 * 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.dbadapter;

import java.sql.*;

/**

 * The Oracle db adapter implementation.

 */

public class DBOracle extends DBAdapter {

  /**

   * The Oracle unique ID generator through use of sequences

   * The name of the sequence used to generate the unique id 

   * is made from the name of the table that uses the id by 

   * appending "_id_seq" to it.

   *

   * @param conn db connection in which to generate the unique id

   * @param tableName the name of table which unique id to generate

   * @exception SQLException <br/> any SQLException that can be thrown 

   *            during the db operation

   * @return return the generated unique id as a long type

   */

  public long getUniqueID(Connection conn, String tableName) 

                                         throws SQLException {

    long uniqueid = 0;

    Statement stmt = conn.createStatement();

    stmt.execute("SELECT " + tableName + "_id_seq.nextval FROM dual");

    ResultSet rs = stmt.getResultSet();

    if ( rs.next() ) {

      uniqueid = rs.getLong(1);

    }

    stmt.close();

    //System.out.println("Unique ID: " + uniqueid);    

    return uniqueid;

  }

  /**

   * The Oracle's function name that gets the current date and time

   * from the database server: "sysdate"

   *

   * @return return the current date and time function name: "sysdate"

   */

  public String getDateString() {

    //System.out.println("Current date string: " + "sysdate");    

    return "sysdate";

  }

  /**

   * The Oracles's string delimiter character: single quote (')

   *

   * @return return the string delimiter: single quote (')

   */

  public String getStringDelimiter() {

    return "'";

  }

}