/*****************************************************************************
* Copyright (C) The Apache Software Foundation. All rights reserved. *
* ------------------------------------------------------------------------- *
* This software is published under the terms of the Apache Software License *
* version 1.1, a copy of which has been included with this distribution in *
* the LICENSE file. *
*****************************************************************************/
package org.apache.cocoon.acting.ModularDatabaseAccess;
import java.sql.Connection;
import java.sql.Statement;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import org.apache.cocoon.environment.Request;
import org.apache.avalon.framework.configuration.Configuration;
import org.apache.avalon.framework.configuration.ConfigurationException;
import org.apache.avalon.framework.thread.ThreadSafe;
import java.lang.Integer;
import java.util.Map;
import java.util.HashMap;
import java.util.SortedSet;
/**
* Abstraction layer to encapsulate different DBMS behaviour for
* autoincrement columns.
*
* Here: manual mode The new value is determined by doing a "select
* max(column)+1 from table" query. With transactions and correct
* isolation levels, this should to the trick almost everywhere.
*
* Note however, that the above query does not prevent a parallel
* transaction to try to insert a row with the same ID since it
* requires only shared locks. C.f. "Phantom Problem"
*
* @author <a href="mailto:haul@apache.org">Christian Haul</a>
* @version CVS $Id: ManualAutoIncrementHelper.java,v 1.1 2002/01/03 12:31:36 giacomo Exp $
*/
public class ManualAutoIncrementHelper extends AbstractAutoIncrementHelper implements ThreadSafe {
private Map selectStatements = new HashMap();
public Object getPostValue( Configuration tableConf, Configuration columnConf, Configuration modenConf,
Connection conn, Statement stmt, Request request )
throws SQLException, ConfigurationException {
return null;
}
public boolean includeInQuery( ) { return true; }
public boolean includeAsValue( ) { return true; }
public Object getPreValue( Configuration tableConf, Configuration columnConf, Configuration modeConf,
Connection conn, Request request )
throws SQLException, ConfigurationException {
/** Set the key value using SELECT MAX(keyname)+1 **/
String tableName = tableConf.getAttribute("name","");
String selectQuery = this.getSelectQuery(tableName, columnConf);
PreparedStatement select_statement = conn.prepareStatement(selectQuery);
ResultSet set = select_statement.executeQuery();
set.next();
int maxid = set.getInt("maxid");
set.close();
select_statement.close();
if (getLogger().isDebugEnabled())
getLogger().debug("autoincrementValue " + (maxid+1));
return new Integer(maxid + 1);
}
public String getSubquery( Configuration tableConf, Configuration columnConf, Configuration modeConf )
throws ConfigurationException {
return null;
}
/**
* Set the String representation of the MaxID lookup statement. This is
* mapped to the Configuration object itself, so if it doesn't exist,
* it will be created.
*/
protected final synchronized void setSelectQuery( String tableName, Configuration entry ) throws ConfigurationException {
StringBuffer queryBuffer = new StringBuffer("SELECT max(");
queryBuffer.append(entry.getAttribute("name"));
queryBuffer.append(") AS maxid FROM ");
queryBuffer.append(tableName);
this.selectStatements.put(entry, queryBuffer.toString());
}
protected final synchronized String getSelectQuery( String tableName, Configuration entry ) throws ConfigurationException {
String result = (String) this.selectStatements.get(entry);
if (result == null) {
setSelectQuery(tableName, entry);
result = (String) this.selectStatements.get(entry);
}
return result;
}
}