001 /* $Id: VariableAttributes.java 471661 2006-11-06 08:09:25Z skitching $ 002 * 003 * Licensed to the Apache Software Foundation (ASF) under one or more 004 * contributor license agreements. See the NOTICE file distributed with 005 * this work for additional information regarding copyright ownership. 006 * The ASF licenses this file to You under the Apache License, Version 2.0 007 * (the "License"); you may not use this file except in compliance with 008 * the License. You may obtain a copy of the License at 009 * 010 * http://www.apache.org/licenses/LICENSE-2.0 011 * 012 * Unless required by applicable law or agreed to in writing, software 013 * distributed under the License is distributed on an "AS IS" BASIS, 014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 015 * See the License for the specific language governing permissions and 016 * limitations under the License. 017 */ 018 019 020 package org.apache.commons.digester.substitution; 021 022 import org.xml.sax.Attributes; 023 024 import java.util.ArrayList; 025 026 027 /** 028 * <p>Wrapper for an org.xml.sax.Attributes object which expands any 029 * "variables" referenced in the attribute value via ${foo} or similar. 030 * This is only done when something actually asks for the attribute value, 031 * thereby imposing no performance penalty if the attribute is not used.</p> 032 * 033 * @since 1.6 034 */ 035 036 public class VariableAttributes implements Attributes { 037 038 // list of mapped attributes. 039 private ArrayList values = new ArrayList(10); 040 041 private Attributes attrs; 042 private VariableExpander expander; 043 044 // ------------------- Public Methods 045 046 /** 047 * Specify which attributes class this object is a proxy for. 048 */ 049 public void init(Attributes attrs, VariableExpander expander) { 050 this.attrs = attrs; 051 this.expander = expander; 052 053 // I hope this doesn't release the memory for this array; for 054 // efficiency, this should just mark the array as being size 0. 055 values.clear(); 056 } 057 058 public String getValue(int index) { 059 if (index >= values.size()) { 060 // Expand the values array with null elements, so the later 061 // call to set(index, s) works ok. 062 // 063 // Unfortunately, there is no easy way to set the size of 064 // an arraylist; we must repeatedly add null elements to it.. 065 values.ensureCapacity(index+1); 066 for(int i = values.size(); i<= index; ++i) { 067 values.add(null); 068 } 069 } 070 071 String s = (String) values.get(index); 072 073 if (s == null) { 074 // we have never been asked for this value before. 075 // get the real attribute value and perform substitution 076 // on it. 077 s = attrs.getValue(index); 078 if (s != null) { 079 s = expander.expand(s); 080 values.set(index, s); 081 } 082 } 083 084 return s; 085 } 086 087 public String getValue(String qname) { 088 int index = attrs.getIndex(qname); 089 if (index == -1) { 090 return null; 091 } 092 return getValue(index); 093 } 094 095 public String getValue(String uri, String localname) { 096 int index = attrs.getIndex(uri, localname); 097 if (index == -1) { 098 return null; 099 } 100 return getValue(index); 101 } 102 103 // plain proxy methods follow : nothing interesting :-) 104 public int getIndex(String qname) { 105 return attrs.getIndex(qname); 106 } 107 108 public int getIndex(String uri, String localpart) { 109 return attrs.getIndex(uri, localpart); 110 } 111 112 public int getLength() { 113 return attrs.getLength(); 114 } 115 116 public String getLocalName(int index) { 117 return attrs.getLocalName(index); 118 } 119 120 public String getQName(int index) { 121 return attrs.getQName(index); 122 } 123 124 public String getType(int index) { 125 return attrs.getType(index); 126 } 127 128 public String getType(String qname) { 129 return attrs.getType(qname); 130 } 131 132 public String getType(String uri, String localname) { 133 return attrs.getType(uri, localname); 134 } 135 136 public String getURI(int index) { 137 return attrs.getURI(index); 138 } 139 140 }