001/*
002// $Id: AxisTransform.java 482 2012-01-05 23:27:27Z jhyde $
003//
004// Licensed to Julian Hyde under one or more contributor license
005// agreements. See the NOTICE file distributed with this work for
006// additional information regarding copyright ownership.
007//
008// Julian Hyde licenses this file to you under the Apache License,
009// Version 2.0 (the "License"); you may not use this file except in
010// compliance with the License. You may obtain a copy of the License at:
011//
012// http://www.apache.org/licenses/LICENSE-2.0
013//
014// Unless required by applicable law or agreed to in writing, software
015// distributed under the License is distributed on an "AS IS" BASIS,
016// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
017// See the License for the specific language governing permissions and
018// limitations under the License.
019*/
020package org.olap4j.transform;
021
022import org.olap4j.Axis;
023import org.olap4j.mdx.*;
024
025/**
026 * Abstract representation of an MDX query transform acting on
027 * a single query axis (e.g. drill-down on member, roll-up, ...)
028 *
029 * @author etdub
030 * @version $Id: AxisTransform.java 482 2012-01-05 23:27:27Z jhyde $
031 * @since Aug 7, 2008
032 *
033 */
034public abstract class AxisTransform implements MdxQueryTransform {
035
036    protected final Axis axis;
037
038    protected AxisTransform(Axis axis) {
039        this.axis = axis;
040    }
041
042    public SelectNode apply(SelectNode sn) {
043        // do a deep copy of the existing query SelectNode before
044        // modifying it:
045        SelectNode newSelectNode = sn.deepCopy();
046
047        for (AxisNode an : newSelectNode.getAxisList()) {
048            if (an.getAxis() == axis) {
049                // this is the axis we're drilling
050
051                ParseTreeNode initialAxisExp = an.getExpression();
052
053                // apply the drill operation
054                ParseTreeNode newAxisExp =
055                    processAxisExp(initialAxisExp);
056
057                // replace the expression in the axis by the new generated one
058                an.setExpression(newAxisExp);
059            }
060        }
061        return newSelectNode;
062    }
063
064    protected abstract ParseTreeNode processAxisExp(ParseTreeNode axisExp);
065
066}
067
068// End AxisTransform.java