001 /*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements. See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership. The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the "License");
007 * you may not use this file except in compliance with the License.
008 * 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 * $Id: AttributesImplSerializer.java 468654 2006-10-28 07:09:23Z minchau $
020 */
021
022 package org.apache.xml.serializer;
023
024 import java.util.Hashtable;
025
026 import org.xml.sax.Attributes;
027 import org.xml.sax.helpers.AttributesImpl;
028
029 /**
030 * This class extends org.xml.sax.helpers.AttributesImpl which implements org.
031 * xml.sax.Attributes. But for optimization this class adds a Hashtable for
032 * faster lookup of an index by qName, which is commonly done in the stream
033 * serializer.
034 *
035 * @see org.xml.sax.Attributes
036 *
037 * @xsl.usage internal
038 */
039 public final class AttributesImplSerializer extends AttributesImpl
040 {
041 /**
042 * Hash table of qName/index values to quickly lookup the index
043 * of an attributes qName. qNames are in uppercase in the hash table
044 * to make the search case insensitive.
045 *
046 * The keys to the hashtable to find the index are either
047 * "prefix:localName" or "{uri}localName".
048 */
049 private final Hashtable m_indexFromQName = new Hashtable();
050
051 private final StringBuffer m_buff = new StringBuffer();
052
053 /**
054 * This is the number of attributes before switching to the hash table,
055 * and can be tuned, but 12 seems good for now - Brian M.
056 */
057 private static final int MAX = 12;
058
059 /**
060 * One less than the number of attributes before switching to
061 * the Hashtable.
062 */
063 private static final int MAXMinus1 = MAX - 1;
064
065 /**
066 * This method gets the index of an attribute given its qName.
067 * @param qname the qualified name of the attribute, e.g. "prefix1:locName1"
068 * @return the integer index of the attribute.
069 * @see org.xml.sax.Attributes#getIndex(String)
070 */
071 public final int getIndex(String qname)
072 {
073 int index;
074
075 if (super.getLength() < MAX)
076 {
077 // if we haven't got too many attributes let the
078 // super class look it up
079 index = super.getIndex(qname);
080 return index;
081 }
082 // we have too many attributes and the super class is slow
083 // so find it quickly using our Hashtable.
084 Integer i = (Integer)m_indexFromQName.get(qname);
085 if (i == null)
086 index = -1;
087 else
088 index = i.intValue();
089 return index;
090 }
091 /**
092 * This method adds the attribute, but also records its qName/index pair in
093 * the hashtable for fast lookup by getIndex(qName).
094 * @param uri the URI of the attribute
095 * @param local the local name of the attribute
096 * @param qname the qualified name of the attribute
097 * @param type the type of the attribute
098 * @param val the value of the attribute
099 *
100 * @see org.xml.sax.helpers.AttributesImpl#addAttribute(String, String, String, String, String)
101 * @see #getIndex(String)
102 */
103 public final void addAttribute(
104 String uri,
105 String local,
106 String qname,
107 String type,
108 String val)
109 {
110 int index = super.getLength();
111 super.addAttribute(uri, local, qname, type, val);
112 // (index + 1) is now the number of attributes
113 // so either compare (index+1) to MAX, or compare index to (MAX-1)
114
115 if (index < MAXMinus1)
116 {
117 return;
118 }
119 else if (index == MAXMinus1)
120 {
121 switchOverToHash(MAX);
122 }
123 else
124 {
125 /* add the key with the format of "prefix:localName" */
126 /* we have just added the attibute, its index is the old length */
127 Integer i = new Integer(index);
128 m_indexFromQName.put(qname, i);
129
130 /* now add with key of the format "{uri}localName" */
131 m_buff.setLength(0);
132 m_buff.append('{').append(uri).append('}').append(local);
133 String key = m_buff.toString();
134 m_indexFromQName.put(key, i);
135 }
136 return;
137 }
138
139 /**
140 * We are switching over to having a hash table for quick look
141 * up of attributes, but up until now we haven't kept any
142 * information in the Hashtable, so we now update the Hashtable.
143 * Future additional attributes will update the Hashtable as
144 * they are added.
145 * @param numAtts
146 */
147 private void switchOverToHash(int numAtts)
148 {
149 for (int index = 0; index < numAtts; index++)
150 {
151 String qName = super.getQName(index);
152 Integer i = new Integer(index);
153 m_indexFromQName.put(qName, i);
154
155 // Add quick look-up to find with uri/local name pair
156 String uri = super.getURI(index);
157 String local = super.getLocalName(index);
158 m_buff.setLength(0);
159 m_buff.append('{').append(uri).append('}').append(local);
160 String key = m_buff.toString();
161 m_indexFromQName.put(key, i);
162 }
163 }
164
165 /**
166 * This method clears the accumulated attributes.
167 *
168 * @see org.xml.sax.helpers.AttributesImpl#clear()
169 */
170 public final void clear()
171 {
172
173 int len = super.getLength();
174 super.clear();
175 if (MAX <= len)
176 {
177 // if we have had enough attributes and are
178 // using the Hashtable, then clear the Hashtable too.
179 m_indexFromQName.clear();
180 }
181
182 }
183
184 /**
185 * This method sets the attributes, previous attributes are cleared,
186 * it also keeps the hashtable up to date for quick lookup via
187 * getIndex(qName).
188 * @param atts the attributes to copy into these attributes.
189 * @see org.xml.sax.helpers.AttributesImpl#setAttributes(Attributes)
190 * @see #getIndex(String)
191 */
192 public final void setAttributes(Attributes atts)
193 {
194
195 super.setAttributes(atts);
196
197 // we've let the super class add the attributes, but
198 // we need to keep the hash table up to date ourselves for the
199 // potentially new qName/index pairs for quick lookup.
200 int numAtts = atts.getLength();
201 if (MAX <= numAtts)
202 switchOverToHash(numAtts);
203
204 }
205
206 /**
207 * This method gets the index of an attribute given its uri and locanName.
208 * @param uri the URI of the attribute name.
209 * @param localName the local namer (after the ':' ) of the attribute name.
210 * @return the integer index of the attribute.
211 * @see org.xml.sax.Attributes#getIndex(String)
212 */
213 public final int getIndex(String uri, String localName)
214 {
215 int index;
216
217 if (super.getLength() < MAX)
218 {
219 // if we haven't got too many attributes let the
220 // super class look it up
221 index = super.getIndex(uri,localName);
222 return index;
223 }
224 // we have too many attributes and the super class is slow
225 // so find it quickly using our Hashtable.
226 // Form the key of format "{uri}localName"
227 m_buff.setLength(0);
228 m_buff.append('{').append(uri).append('}').append(localName);
229 String key = m_buff.toString();
230 Integer i = (Integer)m_indexFromQName.get(key);
231 if (i == null)
232 index = -1;
233 else
234 index = i.intValue();
235 return index;
236 }
237 }