package org.apache.torque.oid;
   
   /* ====================================================================
    * The Apache Software License, Version 1.1
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   *       "This product includes software developed by the
   *        Apache Software Foundation (http://www.apache.org/)."
   *    Alternately, this acknowledgment may appear in the software itself,
   *    if and wherever such third-party acknowledgments normally appear.
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   * This software consists of voluntary contributions made by many
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  import java.math.BigDecimal;
  import java.sql.Connection;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  
  import org.apache.torque.adapter.DB;
  
  import com.workingdogs.village.QueryDataSet;
  import com.workingdogs.village.Record;
  import com.workingdogs.village.Value;
  
  /***
   * This generator works with databases that have an sql syntax for
   * getting an id prior to inserting a row into the database.
   *
   * @author <a href="mailto:jmcnally@collab.net">John D. McNally</a>
   * @version $Id: SequenceIdGenerator.java,v 1.10 2003/08/25 16:33:22 henning Exp $
   */
  public class SequenceIdGenerator implements IdGenerator
  {
      /*** The log. */
      private static Log log = LogFactory.getLog(SequenceIdGenerator.class);
  
      /*** the adapter that knows the correct sql syntax */
      private DB dbAdapter;
  
      /***
       * Creates an IdGenerator which will work with the specified database.
       *
       * @param adapter the adapter that knows the correct sql syntax.
       */
      public SequenceIdGenerator(DB adapter)
      {
          dbAdapter = adapter;
      }
  
      /***
       * Retrieves an id as an int.
       *
       * @param connection A Connection.
       * @param keyInfo an Object that contains additional info.
       * @return An int with the value for the id.
      * @exception Exception Database error.
      */
     public int getIdAsInt(Connection connection, Object keyInfo)
         throws Exception
     {
         return getIdAsVillageValue(connection, keyInfo).asInt();
     }
 
     /***
      * Retrieves an id as an long.
      *
      * @param connection A Connection.
      * @param keyInfo an Object that contains additional info.
      * @return A long with the value for the id.
      * @exception Exception Database error.
      */
     public long getIdAsLong(Connection connection, Object keyInfo)
         throws Exception
     {
         return getIdAsVillageValue(connection, keyInfo).asLong();
     }
 
     /***
      * Retrieves an id as a BigDecimal.
      *
      * @param connection A Connection.
      * @param keyInfo an Object that contains additional info.
      * @return A BigDecimal id
      * @exception Exception Database error.
      */
     public BigDecimal getIdAsBigDecimal(Connection connection, Object keyInfo)
         throws Exception
     {
         return getIdAsVillageValue(connection, keyInfo).asBigDecimal();
     }
 
     /***
      * Retrieves an id as an String.
      *
      * @param connection A Connection.
      * @param keyInfo an Object that contains additional info.
      * @return A String id
      * @exception Exception Database error.
      */
     public String getIdAsString(Connection connection, Object keyInfo)
         throws Exception
     {
         return getIdAsVillageValue(connection, keyInfo).asString();
     }
 
     /***
      * A flag to determine the timing of the id generation
      *
      * @return a <code>boolean</code> value
      */
     public boolean isPriorToInsert()
     {
         return true;
     }
 
     /***
      * A flag to determine the timing of the id generation
      *
      * @return a <code>boolean</code> value
      */
     public boolean isPostInsert()
     {
         return false;
     }
 
     /***
      * A flag to determine whether a Connection is required to
      * generate an id.
      *
      * @return a <code>boolean</code> value
      */
     public boolean isConnectionRequired()
     {
         return true;
     }
 
     /***
      * Retrieves an id as a Village Value.
      *
      * @param connection A Connection.
      * @param keyInfo an Object that contains additional info.
      * @return A Village Value id.
      * @exception Exception Database error.
      */
     private Value getIdAsVillageValue(Connection connection, Object keyInfo)
         throws Exception
     {
         String idSql = dbAdapter.getIDMethodSQL(keyInfo);
         if (log.isDebugEnabled())
         {
             log.debug(idSql);
         }
 
         // Execute the query.
         QueryDataSet qds = new QueryDataSet(connection, idSql);
         Record rec;
         try
         {
             qds.fetchRecords(1);
             rec = qds.getRecord(0);  // Records are 0 based.
         }
         finally
         {
             if (qds != null)
             {
                 qds.close();
             }
         }
         return rec.getValue(1); // Values are 1 based.
     }
 }