001: /*
002: * Copyright (c) 1998-2008 Caucho Technology -- all rights reserved
003: *
004: * This file is part of Resin(R) Open Source
005: *
006: * Each copy or derived work must preserve the copyright notice and this
007: * notice unmodified.
008: *
009: * Resin Open Source is free software; you can redistribute it and/or modify
010: * it under the terms of the GNU General Public License as published by
011: * the Free Software Foundation; either version 2 of the License, or
012: * (at your option) any later version.
013: *
014: * Resin Open Source is distributed in the hope that it will be useful,
015: * but WITHOUT ANY WARRANTY; without even the implied warranty of
016: * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE, or any warranty
017: * of NON-INFRINGEMENT. See the GNU General Public License for more
018: * details.
019: *
020: * You should have received a copy of the GNU General Public License
021: * along with Resin Open Source; if not, write to the
022: * Free Software Foundation, Inc.
023: * 59 Temple Place, Suite 330
024: * Boston, MA 02111-1307 USA
025: *
026: * @author Scott Ferguson
027: */
028:
029: package com.caucho.amber.expr;
030:
031: import com.caucho.amber.query.FromItem;
032: import com.caucho.amber.query.QueryParser;
033: import com.caucho.amber.table.LinkColumns;
034:
035: /**
036: * Links two tables.
037: */
038: abstract public class JoinExpr extends AbstractAmberExpr {
039: /**
040: * Returns true for a boolean expression.
041: */
042: public boolean isBoolean() {
043: return true;
044: }
045:
046: /**
047: * Binds the expression as a select item.
048: */
049: public AmberExpr bindSelect(QueryParser parser) {
050: return this ;
051: }
052:
053: /**
054: * Binds the expression as a select item.
055: */
056: public boolean bindToFromItem() {
057: return false;
058: }
059:
060: /**
061: * Returns the target join clause.
062: */
063: public FromItem getJoinTarget() {
064: return null;
065: }
066:
067: /**
068: * Returns the parent join clause.
069: */
070: public FromItem getJoinParent() {
071: return null;
072: }
073:
074: /**
075: * Returns true if the given from item is the parent link.
076: */
077: public boolean isDependent(FromItem parent, LinkColumns link) {
078: return false;
079: }
080:
081: /**
082: * Returns the where clause once the parent is removed
083: */
084: public AmberExpr getWhere() {
085: return null;
086: }
087:
088: /**
089: * Returns the id expr with the joined expression.
090: */
091: public AmberExpr replace(KeyColumnExpr id) {
092: return id;
093: }
094:
095: /**
096: * Returns the id expr with the joined expression.
097: */
098: public AmberExpr replace(IdExpr id) {
099: return id;
100: }
101: }
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