001 package 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
022 import org.xml.sax.Attributes;
023
024 import 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 */
033 public 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 }