/*
* Copyright (c) 1998-2011 Caucho Technology -- all rights reserved
*
* This file is part of Resin(R) Open Source
*
* Each copy or derived work must preserve the copyright notice and this
* notice unmodified.
*
* Resin Open Source 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.
*
* Resin Open Source 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, or any warranty
* of NON-INFRINGEMENT. See the GNU General Public License for more
* details.
*
* You should have received a copy of the GNU General Public License
* along with Resin Open Source; if not, write to the
* Free Software Foundation, Inc.
* 59 Temple Place, Suite 330
* Boston, MA 02111-1307 USA
*
* @author Scott Ferguson
*/
package com.caucho.amber.expr;
import com.caucho.amber.query.FromItem;
import com.caucho.amber.query.QueryParser;
import com.caucho.amber.table.LinkColumns;
import com.caucho.amber.table.AmberTable;
import com.caucho.util.CharBuffer;
/**
* Represents a member query expression
*/
public class EmptyExpr extends AbstractAmberExpr {
private AmberExpr _collectionExpr;
private String _tableName;
public EmptyExpr(AmberExpr collectionExpr)
{
_collectionExpr = collectionExpr;
}
/**
* Returns true as a boolean expression.
*/
public boolean isBoolean()
{
return true;
}
/**
* Binds the expression as a select item.
*/
public AmberExpr bindSelect(QueryParser parser)
{
_tableName = parser.createTableName();
return this;
}
/**
* Returns true if the expression uses the from item.
*/
public boolean usesFrom(FromItem from, int type, boolean isNot)
{
return (_collectionExpr.usesFrom(from, type));
}
/**
* Returns true if the expression uses the from item.
*/
public AmberExpr replaceJoin(JoinExpr join)
{
_collectionExpr = _collectionExpr.replaceJoin(join);
return this;
}
/**
* Generates the where expression.
*/
public void generateWhere(CharBuffer cb)
{
generateInternalWhere(cb, true);
}
/**
* Generates the (update) where expression.
*/
public void generateUpdateWhere(CharBuffer cb)
{
generateInternalWhere(cb, false);
}
/**
* Generates the having expression.
*/
public void generateHaving(CharBuffer cb)
{
generateWhere(cb);
}
//
// private
private void generateInternalWhere(CharBuffer cb,
boolean select)
{
OneToManyExpr oneToMany = null;
// ManyToMany is implemented as a
// ManyToOne[embeddeding OneToMany]
if (_collectionExpr instanceof ManyToOneExpr) {
PathExpr expr = ((ManyToOneExpr) _collectionExpr).getParent();
if (expr instanceof OneToManyExpr)
oneToMany = (OneToManyExpr) expr;
} else if (_collectionExpr instanceof OneToManyExpr) {
oneToMany = (OneToManyExpr) _collectionExpr;
}
else
throw new UnsupportedOperationException();
LinkColumns join = oneToMany.getLinkColumns();
AmberTable table = join.getSourceTable();
cb.append("EXISTS(SELECT ");
if (table.getIdColumns().size() > 0)
cb.append(table.getIdColumns().get(0).getName());
else
cb.append('*');
cb.append(" FROM " + table.getName() + " " + _tableName);
cb.append(" WHERE ");
String targetTable = oneToMany.getParent().getChildFromItem().getName();
cb.append(join.generateJoin(_tableName, targetTable));
cb.append(')');
}
}