postgresqldatabasepolicy.java

把java对象映射成数据库表中的一条记录

/*
 *
 * The contents of this file are subject to the Mozilla Public License
 * Version 1.1 (the "License"); you may not use this file except in
 * compliance with the License. You may obtain a copy of the License at
 *
 * http://www.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS"
 * basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See the
 * License for the specific language governing rights and limitations under
 * the License.
 *
 * The Original Code is jRelationalFramework.
 *
 * The Initial Developer of the Original Code is is.com.
 * Portions created by is.com are Copyright (C) 2000 is.com.
 * All Rights Reserved.
 *
 * Contributor(s): Tal ([e-mail])
 * Contributor(s): ____________________________________
 *
 * Alternatively, the contents of this file may be used under the terms of
 * the GNU General Public License (the "GPL") or the GNU Lesser General
 * Public license (the "LGPL"), in which case the provisions of the GPL or
 * LGPL are applicable instead of those above.  If you wish to allow use of
 * your version of this file only under the terms of either the GPL or LGPL
 * and not to allow others to use your version of this file under the MPL,
 * indicate your decision by deleting the provisions above and replace them
 * with the notice and other provisions required by either the GPL or LGPL
 * License.  If you do not delete the provisions above, a recipient may use
 * your version of this file under either the MPL or GPL or LGPL License.
 *
 */
package com.is.jrf;


import com.is.util.sql.JDBCHelper;

import java.sql.SQLException;
import java.sql.Timestamp;


/**
 *  Instances of this class perform PostgreSQL-specific logic and return
 *  PostgreSQL-specific information.
 */
public class PostgreSQLDatabasePolicy
    implements DatabasePolicy
  {


  /**
   * This assumes there is a PostgreSQL SEQUENCE object created with name of
   * seq_<i>tableNameHere</i>
   *
   * When executed, this SQL should return a one row, one column result set
   * with an Integer in it that column.
   *
   * @param tableName a value of type 'String'
   * @return a value of type 'String'
   */
  public String sequenceSQL(String tableName)
    {
    return "SELECT NEXTVAL('seq_" + tableName + "')";
    }


  /**
   * This should return the string value (function name) to put into the SQL
   * to tell the database to insert the current timestamp.
   *
   * @return a value of type 'String'
   */
  public String timestampFunction()
    {
    return "timestamp(timestamp 'now')";
    }


  /**
   * The result of this is used in SQL.
   *
   * @param ts a value of type 'Timestamp'
   * @return a value of type 'String'
   */
  public String formatTimestamp(Timestamp ts)
    {
    return (ts == null ?
            "null" :
            "'" + ts.toString() + "'");
    }


  /**
   * The result of this is used in SQL.  This will return only the date
   * (not the time portion)
   *
   * @param sqlDate a value of type 'java.sql.Date'
   * @return a value of type 'String'
   */
  public String formatDate(java.sql.Date sqlDate)
    {
    return (sqlDate == null ?
            "null" :
            "'" + sqlDate.toString() + "'");
    }


  /**
   * This should return the the SQL to use to have the database
   * return the current timestamp.
   *
   * @return a value of type 'String'
   */
  public String currentTimestampSQL()
    {
    return "select now()";
    }


  /**
   * PostgreSQL has Sequences for generating an arbitrary integer primary key so
   * AUTO INCREMENT is not needed here.
   *
   * @return null since PostgreSQL doesn't support the auto-increment method
   */
  public String autoIncrementIdentifier()
    {
    return null;
    }


  /**
   * This method throws an exception since it should never be called.
   *
   * @param tableName a value of type 'String'
   * @param columnName a value of type 'String'
   * @param aJDBCHelper a value of type 'JDBCHelper'
   * @return a value of type 'Long'
   */
  public Long findAutoIncrementId(String tableName,
                                  String columnName,
                                  JDBCHelper aJDBCHelper)
    {
    throw new DatabaseException("This method should never be called.");
    }


  /**
   * This is called when creating a table that has a SEQUENCED_PRIMARY_KEY.
   * If the sequence already exists, it is dropped before being created.
   *
   * @param domain a value of type 'AbstractDomain'
   * @param aJDBCHelper a value of type 'JDBCHelper'
   */
  public void createSequence(AbstractDomain domain,
                             JDBCHelper aJDBCHelper)
          throws SQLException
    {
//      try
//          {
//          aJDBCHelper.executeUpdate("DROP SEQUENCE seq_"
//                                    + domain.getTableName());
//          }
//      catch (SQLException e)
//          {
//          // Ignore this exception since sequence may not be there.
//          }
//      catch (Exception e)
//          {
//          throw new DatabaseException(e);
//          }

    try
        {
        aJDBCHelper.executeUpdate(
            "CREATE SEQUENCE seq_" + domain.getTableName() +
            " INCREMENT 1 START 1 ");
        }
    catch (SQLException e)
        {
        throw e;
        }
    catch (Exception e)
        {
        throw new DatabaseException(e);
        }

    }


  /**
   * Return a string with a name-value pair that represents an SQL outer
   * join in PostgreSQL.  Since we always put the main table on the left, we put
   * the (+) after the right side so that any extra null rows will be
   * generated for the right-hand table.
   *
   * @param mainTableColumn a value of type 'String'
   * @param joinTableColumn a value of type 'String'
   * @return a value of type 'String'
   */
  public String outerWhereJoin(String mainTableColumn,
                               String joinTableColumn)
    {
    return mainTableColumn + " = " + joinTableColumn + " ";
    }

  /**
   * This method used when building SQL for creating a table.
   *
   * @return a value of type 'String'
   */
  public String timestampColumnType()
    {
    return "TIMESTAMP";
    }


  } // PostgreSQLDatabasePolicy