001package org.apache.commons.digester3.substitution;
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
022import org.xml.sax.Attributes;
023
024import java.util.ArrayList;
025
026/**
027 * Wrapper for an {@link Attributes} object which expands any "variables" referenced in the attribute value via
028 * ${foo} or similar. This is only done when something actually asks for the attribute value, thereby imposing no
029 * performance penalty if the attribute is not used.
030 * 
031 * @since 1.6
032 */
033public class VariableAttributes
034    implements Attributes
035{
036
037    // list of mapped attributes.
038    private ArrayList<String> values = new ArrayList<String>( 10 );
039
040    private Attributes attrs;
041
042    private VariableExpander expander;
043
044    // ------------------- Public Methods
045
046    /**
047     * Specify which attributes class this object is a proxy for.
048     *
049     * @param attrs The attributes where variables have to be expanded.
050     * @param expander The variables expander instance.
051     */
052    public void init( Attributes attrs, VariableExpander expander )
053    {
054        this.attrs = attrs;
055        this.expander = expander;
056
057        // I hope this doesn't release the memory for this array; for
058        // efficiency, this should just mark the array as being size 0.
059        values.clear();
060    }
061
062    /**
063     * {@inheritDoc}
064     */
065    public String getValue( int index )
066    {
067        if ( index >= values.size() )
068        {
069            // Expand the values array with null elements, so the later
070            // call to set(index, s) works ok.
071            //
072            // Unfortunately, there is no easy way to set the size of
073            // an arraylist; we must repeatedly add null elements to it..
074            values.ensureCapacity( index + 1 );
075            for ( int i = values.size(); i <= index; ++i )
076            {
077                values.add( null );
078            }
079        }
080
081        String s = values.get( index );
082
083        if ( s == null )
084        {
085            // we have never been asked for this value before.
086            // get the real attribute value and perform substitution
087            // on it.
088            s = attrs.getValue( index );
089            if ( s != null )
090            {
091                s = expander.expand( s );
092                values.set( index, s );
093            }
094        }
095
096        return s;
097    }
098
099    /**
100     * {@inheritDoc}
101     */
102    public String getValue( String qname )
103    {
104        int index = attrs.getIndex( qname );
105        if ( index == -1 )
106        {
107            return null;
108        }
109        return getValue( index );
110    }
111
112    /**
113     * {@inheritDoc}
114     */
115    public String getValue( String uri, String localname )
116    {
117        int index = attrs.getIndex( uri, localname );
118        if ( index == -1 )
119        {
120            return null;
121        }
122        return getValue( index );
123    }
124
125    // plain proxy methods follow : nothing interesting :-)
126    /**
127     * {@inheritDoc}
128     */
129    public int getIndex( String qname )
130    {
131        return attrs.getIndex( qname );
132    }
133
134    /**
135     * {@inheritDoc}
136     */
137    public int getIndex( String uri, String localpart )
138    {
139        return attrs.getIndex( uri, localpart );
140    }
141
142    /**
143     * {@inheritDoc}
144     */
145    public int getLength()
146    {
147        return attrs.getLength();
148    }
149
150    /**
151     * {@inheritDoc}
152     */
153    public String getLocalName( int index )
154    {
155        return attrs.getLocalName( index );
156    }
157
158    /**
159     * {@inheritDoc}
160     */
161    public String getQName( int index )
162    {
163        return attrs.getQName( index );
164    }
165
166    /**
167     * {@inheritDoc}
168     */
169    public String getType( int index )
170    {
171        return attrs.getType( index );
172    }
173
174    /**
175     * {@inheritDoc}
176     */
177    public String getType( String qname )
178    {
179        return attrs.getType( qname );
180    }
181
182    /**
183     * {@inheritDoc}
184     */
185    public String getType( String uri, String localname )
186    {
187        return attrs.getType( uri, localname );
188    }
189
190    /**
191     * {@inheritDoc}
192     */
193    public String getURI( int index )
194    {
195        return attrs.getURI( index );
196    }
197
198}