001    package org.apache.torque.engine.database.model;
002    
003    /*
004     * Licensed to the Apache Software Foundation (ASF) under one
005     * or more contributor license agreements.  See the NOTICE file
006     * distributed with this work for additional information
007     * regarding copyright ownership.  The ASF licenses this file
008     * to you under the Apache License, Version 2.0 (the
009     * "License"); you may not use this file except in compliance
010     * 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,
015     * software distributed under the License is distributed on an
016     * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
017     * KIND, either express or implied.  See the License for the
018     * specific language governing permissions and limitations
019     * under the License.
020     */
021    
022    import java.util.List;
023    
024    /**
025     * Information about unique columns of a table.  This class assumes
026     * that in the underlying RDBMS, unique constraints and unique indices
027     * are roughly equivalent.  For example, adding a unique constraint to
028     * a column also creates an index on that column (this is known to be
029     * true for MySQL and Oracle).
030     *
031     * @author <a href="mailto:jvanzyl@apache.org">Jason van Zyl</a>
032     * @author <a href="mailto:dlr@collab.net">Daniel Rall</a>
033     * @version $Id: Unique.java,v 1.1 2007-10-21 07:57:27 abyrne Exp $
034     */
035    public class Unique extends Index
036    {
037        /**
038         * Returns <code>true</code>.
039         *
040         * @return true
041         */
042        public final boolean isUnique()
043        {
044            return true;
045        }
046    
047        /**
048         * String representation of the index. This is an xml representation.
049         *
050         * @return string representation in xml
051         */
052        public String toString()
053        {
054            StringBuffer result = new StringBuffer();
055            result.append(" <unique name=\"")
056                .append(getName())
057                .append("\">\n");
058    
059            List columns = getColumns();
060            for (int i = 0; i < columns.size(); i++)
061            {
062                result.append("  <unique-column name=\"")
063                    .append(columns.get(i))
064                    .append("\"/>\n");
065            }
066            result.append(" </unique>\n");
067            return result.toString();
068        }
069    }