001 package org.apache.commons.digester3;
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.ArrayList;
023 import java.util.Collections;
024 import java.util.Comparator;
025 import java.util.HashMap;
026 import java.util.Iterator;
027 import java.util.List;
028 import java.util.Map;
029
030 import org.xml.sax.Attributes;
031
032 /**
033 * <p>
034 * Extension of {@link RulesBase} for complex schema.
035 * </p>
036 * <p>
037 * This is an extension of the basic pattern matching scheme intended to improve support for mapping complex xml-schema.
038 * It is intended to be a minimal extension of the standard rules big enough to support complex schema but without the
039 * full generality offered by more exotic matching pattern rules.
040 * </p>
041 * <h4>When should you use this rather than the original?</h4>
042 * <p>
043 * This pattern-matching engine is complex and slower than the basic default RulesBase class, but offers more
044 * functionality:
045 * <ul>
046 * <li>Universal patterns allow patterns to be specified which will match regardless of whether there are
047 * "better matching" patterns available.</li>
048 * <li>Parent-match patterns (eg "a/b/?") allow matching for all direct children of a specified element.</li>
049 * <li>Ancestor-match patterns (eg "a/b/*") allow matching all elements nested within a specified element to any nesting
050 * depth.</li>
051 * <li>Completely-wild patterns ("*" or "!*") allow matching all elements.</li>
052 * </ul>
053 * </p>
054 * <h4>Universal Match Patterns</h4>
055 * <p>
056 * The default RulesBase pattern-matching engine always attempts to find the "best matching pattern", and will ignore
057 * rules associated with other patterns that match but are not "as good". As an example, if the pattern "a/b/c" is
058 * associated with rules 1 and 2, and "*/c" is associated with rules 3 and 4 then element "a/b/c" will cause only
059 * rules 1 and 2 to execute. Rules 3 and 4 do have matching patterns, but because the patterns are shorter and include
060 * wildcard characters they are regarded as being "not as good" as a direct match. In general, exact patterns are better
061 * than wildcard patterns, and among multiple patterns with wildcards, the longest is preferred. See the RulesBase class
062 * for more information.
063 * </p>
064 * <p>
065 * This feature of preferring "better" patterns can be a powerful tool. However it also means that patterns can interact
066 * in unexpected ways.
067 * </p>
068 * <p>
069 * When using the ExtendedBaseRules, any pattern prefixed with '!' bypasses the "best match" feature. Even if there is
070 * an exact match or a longer wildcard match, patterns prefixed by '!' will still be tested to see if they match, and if
071 * so their associated Rule objects will be included in the set of rules to be executed in the normal manner.
072 * </p>
073 * <ul>
074 * <li>Pattern <code>"!*/a/b"</code> matches whenever an 'b' element is inside an 'a'.</li>
075 * <li>Pattern <code>"!a/b/?"</code> matches any child of a parent matching <code>"a/b"</code> (see
076 * "Parent Match Patterns").</li>
077 * <li>Pattern <code>"!*/a/b/?"</code> matches any child of a parent matching <code>"!*/a/b"</code> (see
078 * "Parent Match Patterns").</li>
079 * <li>Pattern <code>"!a/b/*"</code> matches any element whose path starts with "a" then "b" (see
080 * "Ancestor Match Patterns").</li>
081 * <li>Pattern <code>"!*/a/b/*"</code> matches any elements whose path contains 'a/b' (see
082 * "Ancestor Match Patterns").</li>
083 * </ul>
084 * <h4>Parent Match Patterns</h4>
085 * <p>
086 * These will match direct child elements of a particular parent element.
087 * <ul>
088 * <li>
089 * <code>"a/b/c/?"</code> matches any child whose parent matches <code>"a/b/c"</code>. Exact parent rules take
090 * precedence over Ancestor Match patterns.</li>
091 * <li>
092 * <code>"*/a/b/c/?"</code> matches any child whose parent matches <code>"*/a/b/c"</code>. The longest
093 * matching still applies to parent matches but the length excludes the '?', which effectively means that standard
094 * wildcard matches with the same level of depth are chosen in preference.</li>
095 * </ul>
096 * </p>
097 * <h4>Ancestor Match Patterns</h4>
098 * <p>
099 * These will match elements whose parentage includes a particular sequence of elements.
100 * <ul>
101 * <li>
102 * <code>"a/b/*"</code> matches any element whose path starts with 'a' then 'b'. Exact parent and parent match rules
103 * take precedence. The longest ancestor match will take precedence.</li>
104 * <li>
105 * <code>"*/a/b/*"</code> matches any elements whose path contains an element 'a' followed by an element 'b'.
106 * The longest matching still applies but the length excludes the '*' at the end.</li>
107 * </ul>
108 * </p>
109 * <h4>Completely Wild Patterns</h4>
110 * <p>
111 * Pattern <code>"*"</code> matches every pattern that isn't matched by any other basic rule.
112 * </p>
113 * <p>
114 * Pattern <code>"!*"</code> matches every pattern.
115 * </p>
116 * <h4>Using The Extended Rules</h4>
117 * <p>
118 * By default, a Digester instance uses a {@link RulesBase} instance as its pattern matching engine. To use an
119 * ExtendedBaseRules instance, call the Digester.setRules method before adding any Rule objects to the digester
120 * instance:
121 *
122 * <pre>
123 * Digester digester = new Digester();
124 * digester.setRules( new ExtendedBaseRules() );
125 * </pre>
126 *
127 * </p>
128 * <p>
129 * The most important thing to remember when using the extended rules is that universal and non-universal patterns are
130 * completely independent. Universal patterns are never affected by the addition of new patterns or the removal of
131 * existing ones. Non-universal patterns are never affected by the addition of new <em>universal</em> patterns or the
132 * removal of existing <em>universal</em> patterns. As in the basic matching rules, non-universal (basic) patterns
133 * <strong>can</strong> be affected by the addition of new <em>non-universal</em> patterns or the removal of existing
134 * <em>non-universal</em> patterns, because only rules associated with the "best matching" pattern for each xml element
135 * are executed.
136 * <p>
137 * This means that you can use universal patterns to build up the simple parts of your structure - for example defining
138 * universal creation and property setting rules. More sophisticated and complex mapping will require non-universal
139 * patterns and this might mean that some of the universal rules will need to be replaced by a series of special cases
140 * using non-universal rules. But by using universal rules as your backbone, these additions should not break your
141 * existing rules.
142 * </p>
143 */
144 public class ExtendedBaseRules
145 extends RulesBase
146 {
147
148 // ----------------------------------------------------- Instance Variables
149
150 /**
151 * Counts the entry number for the rules.
152 */
153 private int counter = 0;
154
155 /**
156 * The decision algorithm used (unfortunately) doesn't preserve the entry order. This map is used by a comparator
157 * which orders the list of matches before it's returned. This map stores the entry number keyed by the rule.
158 */
159 private Map<Rule, Integer> order = new HashMap<Rule, Integer>();
160
161 // --------------------------------------------------------- Public Methods
162
163 /**
164 * {@inheritDoc}
165 */
166 @Override
167 protected void registerRule( String pattern, Rule rule )
168 {
169 super.registerRule( pattern, rule );
170 counter++;
171 order.put( rule, counter );
172 }
173
174 /**
175 * {@inheritDoc}
176 */
177 @Override
178 public List<Rule> match( String namespaceURI, String pattern, String name, Attributes attributes )
179 {
180 // calculate the pattern of the parent
181 // (if the element has one)
182 String parentPattern = "";
183 int lastIndex = pattern.lastIndexOf( '/' );
184
185 boolean hasParent = true;
186 if ( lastIndex == -1 )
187 {
188 // element has no parent
189 hasParent = false;
190 }
191 else
192 {
193 // calculate the pattern of the parent
194 parentPattern = pattern.substring( 0, lastIndex );
195 }
196
197 // we keep the list of universal matches separate
198 List<Rule> universalList = new ArrayList<Rule>( counter );
199
200 // Universal wildcards ('*') in the middle of the pattern-string
201 List<Rule> recList = null;
202 // temporary parentPattern
203 // we don't want to change anything....
204 String tempParentPattern = parentPattern;
205 int parentLastIndex = tempParentPattern.lastIndexOf( '/' );
206 // look for pattern. Here, we search the whole
207 // parent. Not ideal, but does the thing....
208 while ( parentLastIndex > -1 && recList == null )
209 {
210 recList = this.cache.get( tempParentPattern + "/*/" + pattern.substring( lastIndex + 1 ) );
211 if ( recList != null )
212 {
213 // when /*/-pattern-string is found, add method
214 // list to universalList.
215 // Digester will do the rest
216 universalList.addAll( recList );
217 }
218 else
219 {
220 // if not, shorten tempParent to move /*/ one position
221 // to the left.
222 // as last part of patttern is always added
223 // we make sure pattern is allowed anywhere.
224 tempParentPattern = parentPattern.substring( 0, parentLastIndex );
225 }
226
227 parentLastIndex = tempParentPattern.lastIndexOf( '/' );
228 }
229
230 // Universal all wildards ('!*')
231 // These are always matched so always add them
232 List<Rule> tempList = this.cache.get( "!*" );
233 if ( tempList != null )
234 {
235 universalList.addAll( tempList );
236 }
237
238 // Universal exact parent match
239 // need to get this now since only wildcards are considered later
240 tempList = this.cache.get( "!" + parentPattern + "/?" );
241 if ( tempList != null )
242 {
243 universalList.addAll( tempList );
244 }
245
246 // base behaviour means that if we certain matches, we don't continue
247 // but we just have a single combined loop and so we have to set
248 // a variable
249 boolean ignoreBasicMatches = false;
250
251 // see if we have an exact basic pattern match
252 List<Rule> rulesList = this.cache.get( pattern );
253 if ( rulesList != null )
254 {
255 // we have a match!
256 // so ignore all basic matches from now on
257 ignoreBasicMatches = true;
258
259 }
260 else
261 {
262
263 // see if we have an exact child match
264 if ( hasParent )
265 {
266 // matching children takes preference
267 rulesList = this.cache.get( parentPattern + "/?" );
268 if ( rulesList != null )
269 {
270 // we have a match!
271 // so ignore all basic matches from now on
272 ignoreBasicMatches = true;
273
274 }
275 else
276 {
277 // we don't have a match yet - so try exact ancester
278 //
279 rulesList = findExactAncesterMatch( pattern );
280 if ( rulesList != null )
281 {
282 // we have a match!
283 // so ignore all basic matches from now on
284 ignoreBasicMatches = true;
285 }
286 }
287 }
288 }
289
290 // OK - we're ready for the big loop!
291 // Unlike the basic rules case,
292 // we have to go through for all those universal rules in all cases.
293
294 // Find the longest key, ie more discriminant
295 int longKeyLength = 0;
296
297 for ( String key : this.cache.keySet() )
298 {
299
300 // find out if it's a univeral pattern
301 // set a flag
302 boolean isUniversal = key.startsWith( "!" );
303 if ( isUniversal )
304 {
305 // and find the underlying key
306 key = key.substring( 1, key.length() );
307 }
308
309 // don't need to check exact matches
310 boolean wildcardMatchStart = key.startsWith( "*/" );
311 boolean wildcardMatchEnd = key.endsWith( "/*" );
312 if ( wildcardMatchStart || ( isUniversal && wildcardMatchEnd ) )
313 {
314
315 boolean parentMatched = false;
316 boolean basicMatched = false;
317 boolean ancesterMatched = false;
318
319 boolean parentMatchEnd = key.endsWith( "/?" );
320 if ( parentMatchEnd )
321 {
322 // try for a parent match
323 parentMatched = parentMatch( key, parentPattern );
324
325 }
326 else if ( wildcardMatchEnd )
327 {
328 // check for ancester match
329 if ( wildcardMatchStart )
330 {
331 String patternBody = key.substring( 2, key.length() - 2 );
332 if ( pattern.endsWith( patternBody ) )
333 {
334 ancesterMatched = true;
335 }
336 else
337 {
338 ancesterMatched = ( pattern.indexOf( patternBody + "/" ) > -1 );
339 }
340 }
341 else
342 {
343 String bodyPattern = key.substring( 0, key.length() - 2 );
344 if ( pattern.startsWith( bodyPattern ) )
345 {
346 if ( pattern.length() == bodyPattern.length() )
347 {
348 // exact match
349 ancesterMatched = true;
350 }
351 else
352 {
353 ancesterMatched = ( pattern.charAt( bodyPattern.length() ) == '/' );
354 }
355 }
356 else
357 {
358 ancesterMatched = false;
359 }
360 }
361 }
362 else
363 {
364 // try for a base match
365 basicMatched = basicMatch( key, pattern );
366 }
367
368 if ( parentMatched || basicMatched || ancesterMatched )
369 {
370 if ( isUniversal )
371 {
372 // universal rules go straight in
373 // (no longest matching rule)
374 tempList = this.cache.get( "!" + key );
375 if ( tempList != null )
376 {
377 universalList.addAll( tempList );
378 }
379
380 }
381 else
382 {
383 if ( !ignoreBasicMatches )
384 {
385 // ensure that all parent matches are SHORTER
386 // than rules with same level of matching.
387 //
388 // the calculations below don't work for universal
389 // matching, but we don't care because in that case
390 // this if-stmt is not entered.
391 int keyLength = key.length();
392 if ( wildcardMatchStart )
393 {
394 --keyLength;
395 }
396 if ( wildcardMatchEnd )
397 {
398 --keyLength;
399 }
400 else if ( parentMatchEnd )
401 {
402 --keyLength;
403 }
404
405 if ( keyLength > longKeyLength )
406 {
407 rulesList = this.cache.get( key );
408 longKeyLength = keyLength;
409 }
410 }
411 }
412 }
413 }
414 }
415
416 // '*' works in practice as a default matching
417 // (this is because anything is a deeper match!)
418 if ( rulesList == null )
419 {
420 rulesList = this.cache.get( "*" );
421 }
422
423 // if we've matched a basic pattern, then add to the universal list
424 if ( rulesList != null )
425 {
426 universalList.addAll( rulesList );
427 }
428
429 // don't filter if namespace is null
430 if ( namespaceURI != null )
431 {
432 // remove invalid namespaces
433 Iterator<Rule> it = universalList.iterator();
434 while ( it.hasNext() )
435 {
436 Rule rule = it.next();
437 String nsUri = rule.getNamespaceURI();
438 if ( nsUri != null && !nsUri.equals( namespaceURI ) )
439 {
440 it.remove();
441 }
442 }
443 }
444
445 // need to make sure that the collection is sort in the order
446 // of addition. We use a custom comparator for this
447 Collections.sort( universalList, new Comparator<Rule>()
448 {
449
450 public int compare( Rule r1, Rule r2 )
451 {
452 // Get the entry order from the map
453 Integer i1 = order.get( r1 );
454 Integer i2 = order.get( r2 );
455
456 // and use that to perform the comparison
457 if ( i1 == null )
458 {
459 if ( i2 == null )
460 {
461
462 return 0;
463
464 }
465 return -1;
466 }
467 else if ( i2 == null )
468 {
469 return 1;
470 }
471
472 return ( i1.intValue() - i2.intValue() );
473 }
474 } );
475
476 return universalList;
477 }
478
479 /**
480 * Checks the input parentPattern contains the input key at the end.
481 *
482 * @param key The key to be found
483 * @param parentPattern The pattern where looking for the key
484 * @return true, if {@code key} is found inside {@code parentPattern}, false otherwise
485 */
486 private boolean parentMatch( String key, String parentPattern )
487 {
488 return parentPattern.endsWith( key.substring( 1, key.length() - 2 ) );
489 }
490
491 /**
492 * Standard match. Matches the end of the pattern to the key.
493 *
494 * @param key The key to be found
495 * @param pattern The pattern where looking for the key
496 * @return true, if {@code key} is found inside {@code pattern}, false otherwise
497 */
498 private boolean basicMatch( String key, String pattern )
499 {
500 return ( pattern.equals( key.substring( 2 ) ) || pattern.endsWith( key.substring( 1 ) ) );
501 }
502
503 /**
504 * Finds an exact ancester match for given pattern
505 *
506 * @param parentPattern The input pattern
507 * @return A list of {@code Rule} related to the input pattern
508 */
509 private List<Rule> findExactAncesterMatch( String parentPattern )
510 {
511 List<Rule> matchingRules = null;
512 int lastIndex = parentPattern.length();
513 while ( lastIndex-- > 0 )
514 {
515 lastIndex = parentPattern.lastIndexOf( '/', lastIndex );
516 if ( lastIndex > 0 )
517 {
518 matchingRules = this.cache.get( parentPattern.substring( 0, lastIndex ) + "/*" );
519 if ( matchingRules != null )
520 {
521 return matchingRules;
522 }
523 }
524 }
525 return null;
526 }
527
528 }