instantdbdatabasepolicy.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): Jonathan Carlson ([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.lang.reflect.Method;

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

import org.apache.log4j.Category;


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

  private static final Category LOG =
                Category.getInstance("InstantDBDatabasePolicy.class.getName()");

  /**
   * InstantDB uses AUTO INCREMENT at time of insert instead of sequences.
   *
   * @param tableName a value of type 'String'
   * @return a value of type 'String'
   */
  public String sequenceSQL(String tableName)
    {
    return null;
    }

  public void createSequence(AbstractDomain domain, JDBCHelper aJDBCHelper)
          throws SQLException
    {
    }


  /**
   * This is 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 "NOW";
    }


  /**
   * The return value should be in the format that the database recognizes
   * for a timestamp.
   *
   * @param ts a value of type 'Timestamp'
   * @return a value of type 'String'
   */
  public String formatTimestamp(Timestamp ts)
    {
    return "'" + 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 sysdate = NOW";
    }


  /**
   *  InstantDB uses auto-increment for assigning arbitrary primary key ids.
   *
   * @return a value of type 'String'
   */
  public String autoIncrementIdentifier()
    {
    return "AUTO INCREMENT";
    }


  /**
   * This method uses a proprietary InstantDB extension.  We have to use
   * reflection here since we are calling a non-standard method and we can't
   * expect the InstantDB connection class to be available at compile time.
   *
   * @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)
    {
    Class connectionClass = null;
    try
        {
        connectionClass = aJDBCHelper.getConnection().getClass();
        }
    catch (Exception e)
        {
        throw new DatabaseException(e);
        }
    Class[] parmClasses = {String.class, String.class};
    String[] parms = {tableName, columnName};
    Method method = null;
    Long id = null;
    try
        {
        method = connectionClass.getMethod("getLastValueInserted",
                                           parmClasses);
        Object obj = method.invoke(aJDBCHelper.getConnection(), parms);
        if (obj instanceof Integer)
            {
            Integer intID = (Integer) obj;
            id = new Long(intID.intValue());
            }
        else  // assume it's a Long
            {
            id = (Long) obj;
            }
        }
    catch (Exception e)
        {
        LOG.error(
            "Reflection error in "
            + "InstantDBDatabasePolicy#findAutoIncrementId(...)",
            e);
        throw new ConfigurationException(e.fillInStackTrace().toString());
        }
    return id;
    }


  /**
   * Outer WHERE joins are not supported in InstantDB, so this just returns
   * a normal join.
   *
   * @param mainTableColumn a value of type 'String'
   * @param joinTableColumn a value of type 'String'
   * @param sqlBuffer a value of type 'StringBuffer'
   * @return a value of type 'String'
   */
  public String outerWhereJoin(String mainTableColumn,
                               String joinTableColumn)
    {
    return mainTableColumn + "=" + joinTableColumn + " ";
    }


  /**
   * This method is used when building SQL to create tables.
   *
   * @return a value of type 'String'
   */
  public String timestampColumnType()
    {
    return "TIMESTAMP";
    }


  } // InstantDBDatabasePolicy