001 /* $Id: ExtendedBaseRules.java 729096 2008-12-23 20:35:24Z rahul $ 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; 021 022 023 import java.util.ArrayList; 024 import java.util.Collections; 025 import java.util.Comparator; 026 import java.util.HashMap; 027 import java.util.Iterator; 028 import java.util.List; 029 import java.util.Map; 030 031 032 /** 033 * <p>Extension of {@link RulesBase} for complex schema.</p> 034 * 035 * <p>This is an extension of the basic pattern matching scheme 036 * intended to improve support for mapping complex xml-schema. 037 * It is intended to be a minimal extension of the standard rules 038 * big enough to support complex schema but without the full generality 039 * offered by more exotic matching pattern rules.</p> 040 * 041 * <h4>When should you use this rather than the original?</h4> 042 * 043 * <p> 044 * This pattern-matching engine is complex and slower than the basic 045 * default RulesBase class, but offers more functionality: 046 * <ul> 047 * <li>Universal patterns allow patterns to be specified which will match 048 * regardless of whether there are "better matching" patterns available.</li> 049 * <li>Parent-match patterns (eg "a/b/?") allow matching for all direct 050 * children of a specified element.</li> 051 * <li>Ancestor-match patterns (eg "a/b/*") allow matching all elements 052 * nested within a specified element to any nesting depth.</li> 053 * <li>Completely-wild patterns ("*" or "!*") allow matching all elements.</li> 054 * </ul> 055 * </p> 056 * 057 * <h4>Universal Match Patterns</h4> 058 * 059 * <p>The default RulesBase pattern-matching engine always attempts to find 060 * the "best matching pattern", and will ignore rules associated with other 061 * patterns that match but are not "as good". As an example, if the pattern 062 * "a/b/c" is associated with rules 1 and 2, and "*/c" is associated with 063 * rules 3 and 4 then element "a/b/c" will cause only rules 1 and 2 to execute. 064 * Rules 3 and 4 do have matching patterns, but because the patterns are shorter 065 * and include wildcard characters they are regarded as being "not as good" as 066 * a direct match. In general, exact patterns are better than wildcard patterns, 067 * and among multiple patterns with wildcards, the longest is preferred. 068 * See the RulesBase class for more information.</p> 069 * 070 * <p>This feature of preferring "better" patterns can be a powerful tool. 071 * However it also means that patterns can interact in unexpected ways.</p> 072 * 073 * <p>When using the ExtendedBaseRules, any pattern prefixed with '!' bypasses 074 * the "best match" feature. Even if there is an exact match or a longer 075 * wildcard match, patterns prefixed by '!' will still be tested to see if 076 * they match, and if so their associated Rule objects will be included in 077 * the set of rules to be executed in the normal manner.</p> 078 * 079 * <ul> 080 * <li>Pattern <code>"!*/a/b"</code> matches whenever an 'b' element 081 * is inside an 'a'.</li> 082 * <li>Pattern <code>"!a/b/?"</code> matches any child of a parent 083 * matching <code>"a/b"</code> (see "Parent Match Patterns").</li> 084 * <li>Pattern <code>"!*/a/b/?"</code> matches any child of a parent 085 * matching <code>"!*/a/b"</code> (see "Parent Match Patterns").</li> 086 * <li>Pattern <code>"!a/b/*"</code> matches any element whose path 087 * starts with "a" then "b" (see "Ancestor Match Patterns").</li> 088 * <li>Pattern <code>"!*/a/b/*"</code> matches any elements whose path 089 * contains 'a/b' (see "Ancestor Match Patterns").</li> 090 * </ul> 091 * 092 * <h4>Parent Match Patterns</h4> 093 * 094 * <p> 095 * These will match direct child elements of a particular parent element. 096 * <ul> 097 * <li> 098 * <code>"a/b/c/?"</code> matches any child whose parent matches 099 * <code>"a/b/c"</code>. Exact parent rules take precedence over Ancestor 100 * Match patterns. 101 * </li> 102 * <li> 103 * <code>"*/a/b/c/?"</code> matches any child whose parent matches 104 * <code>"*/a/b/c"</code>. The longest matching still applies to parent 105 * matches but the length excludes the '?', which effectively means 106 * that standard wildcard matches with the same level of depth are 107 * chosen in preference. 108 * </li> 109 * </ul> 110 * </p> 111 * 112 * <h4>Ancestor Match Patterns</h4> 113 * 114 * <p> 115 * These will match elements whose parentage includes a particular sequence 116 * of elements. 117 * <ul> 118 * <li> 119 * <code>"a/b/*"</code> matches any element whose path starts with 120 * 'a' then 'b'. Exact parent and parent match rules take precedence. 121 * The longest ancestor match will take precedence. 122 * </li> 123 * <li> 124 * <code>"*/a/b/*"</code> matches any elements whose path contains 125 * an element 'a' followed by an element 'b'. The longest matching still 126 * applies but the length excludes the '*' at the end. 127 * </li> 128 * </ul> 129 * </p> 130 * 131 * <h4>Completely Wild Patterns</h4> 132 * 133 * <p>Pattern <code>"*"</code> matches every pattern that isn't matched by 134 * any other basic rule.</p> 135 * 136 * <p>Pattern <code>"!*"</code> matches every pattern.</p> 137 * 138 * <h4>Using The Extended Rules</h4> 139 * 140 * <p>By default, a Digester instance uses a {@link RulesBase} instance as 141 * its pattern matching engine. To use an ExtendedBaseRules instance, call 142 * the Digester.setRules method before adding any Rule objects to the digester 143 * instance: 144 * <pre> 145 * Digester digester = new Digester(); 146 * digester.setRules( new ExtendedBaseRules() ); 147 * </pre></p> 148 * 149 * <p>The most important thing to remember when using the extended rules is 150 * that universal and non-universal patterns are completely independent. 151 * Universal patterns are never affected by the addition of new patterns 152 * or the removal of existing ones. Non-universal patterns are never affected 153 * by the addition of new <em>universal</em> patterns or the removal of 154 * existing <em>universal</em> patterns. As in the basic matching rules, 155 * non-universal (basic) patterns <strong>can</strong> be affected by the 156 * addition of new <em>non-universal</em> patterns or the removal of existing 157 * <em>non-universal</em> patterns, because only rules associated with the 158 * "best matching" pattern for each xml element are executed. 159 * 160 * <p> This means that you can use universal patterns to build up the simple 161 * parts of your structure - for example defining universal creation and 162 * property setting rules. More sophisticated and complex mapping will require 163 * non-universal patterns and this might mean that some of the universal rules 164 * will need to be replaced by a series of special cases using non-universal 165 * rules. But by using universal rules as your backbone, these additions 166 * should not break your existing rules.</p> 167 */ 168 169 170 public class ExtendedBaseRules extends RulesBase { 171 172 173 // ----------------------------------------------------- Instance Variables 174 175 /** 176 * Counts the entry number for the rules. 177 */ 178 private int counter = 0; 179 180 181 /** 182 * The decision algorithm used (unfortunately) doesn't preserve the entry 183 * order. 184 * This map is used by a comparator which orders the list of matches 185 * before it's returned. 186 * This map stores the entry number keyed by the rule. 187 */ 188 private Map<Rule, Integer> order = new HashMap<Rule, Integer>(); 189 190 191 // --------------------------------------------------------- Public Methods 192 193 194 /** 195 * Register a new Rule instance matching the specified pattern. 196 * 197 * @param pattern Nesting pattern to be matched for this Rule 198 * @param rule Rule instance to be registered 199 */ 200 public void add(String pattern, Rule rule) { 201 super.add(pattern, rule); 202 counter++; 203 order.put(rule, counter); 204 } 205 206 207 /** 208 * Return a List of all registered Rule instances that match the specified 209 * nesting pattern, or a zero-length List if there are no matches. If more 210 * than one Rule instance matches, they <strong>must</strong> be returned 211 * in the order originally registered through the <code>add()</code> 212 * method. 213 * 214 * @param pattern Nesting pattern to be matched 215 */ 216 public List<Rule> match(String namespace, String pattern) { 217 // calculate the pattern of the parent 218 // (if the element has one) 219 String parentPattern = ""; 220 int lastIndex = pattern.lastIndexOf('/'); 221 222 boolean hasParent = true; 223 if (lastIndex == -1) { 224 // element has no parent 225 hasParent = false; 226 227 } else { 228 // calculate the pattern of the parent 229 parentPattern = pattern.substring(0, lastIndex); 230 231 } 232 233 234 // we keep the list of universal matches separate 235 List<Rule> universalList = new ArrayList<Rule>(counter); 236 237 // Universal all wildards ('!*') 238 // These are always matched so always add them 239 List<Rule> tempList = this.cache.get("!*"); 240 if (tempList != null) { 241 universalList.addAll(tempList); 242 } 243 244 // Universal exact parent match 245 // need to get this now since only wildcards are considered later 246 tempList = this.cache.get("!" + parentPattern + "/?"); 247 if (tempList != null) { 248 universalList.addAll(tempList); 249 } 250 251 252 // base behaviour means that if we certain matches, we don't continue 253 // but we just have a single combined loop and so we have to set 254 // a variable 255 boolean ignoreBasicMatches = false; 256 257 258 // see if we have an exact basic pattern match 259 List<Rule> rulesList = this.cache.get(pattern); 260 if (rulesList != null) { 261 // we have a match! 262 // so ignore all basic matches from now on 263 ignoreBasicMatches = true; 264 265 } else { 266 267 // see if we have an exact child match 268 if (hasParent) { 269 // matching children takes preference 270 rulesList = this.cache.get(parentPattern + "/?"); 271 if (rulesList != null) { 272 // we have a match! 273 // so ignore all basic matches from now on 274 ignoreBasicMatches = true; 275 276 } else { 277 // we don't have a match yet - so try exact ancester 278 // 279 rulesList = findExactAncesterMatch(pattern); 280 if (rulesList != null) { 281 // we have a match! 282 // so ignore all basic matches from now on 283 ignoreBasicMatches = true; 284 } 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 String longKey = ""; 296 int longKeyLength = 0; 297 298 for (String key : this.cache.keySet()) { 299 300 // find out if it's a univeral pattern 301 // set a flag 302 boolean isUniversal = key.startsWith("!"); 303 if (isUniversal) { 304 // and find the underlying key 305 key = key.substring(1, key.length()); 306 } 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 boolean parentMatched = false; 315 boolean basicMatched = false; 316 boolean ancesterMatched = false; 317 318 boolean parentMatchEnd = key.endsWith("/?"); 319 if (parentMatchEnd) { 320 // try for a parent match 321 parentMatched = parentMatch(key, pattern, parentPattern); 322 323 } else if (wildcardMatchEnd) { 324 // check for ancester match 325 if (wildcardMatchStart) { 326 String patternBody = key.substring(2, key.length() - 2); 327 if (pattern.endsWith(patternBody)) { 328 ancesterMatched = true; 329 } else { 330 ancesterMatched = (pattern.indexOf(patternBody + "/") > -1); 331 } 332 } else { 333 String bodyPattern = key.substring(0, key.length() - 2); 334 if (pattern.startsWith(bodyPattern)) 335 { 336 if (pattern.length() == bodyPattern.length()) { 337 // exact match 338 ancesterMatched = true; 339 } else { 340 ancesterMatched = ( pattern.charAt(bodyPattern.length()) == '/' ); 341 } 342 } else { 343 ancesterMatched = false; 344 } 345 } 346 } else { 347 // try for a base match 348 basicMatched = basicMatch(key, pattern); 349 } 350 351 if (parentMatched || basicMatched || ancesterMatched) { 352 if (isUniversal) { 353 // universal rules go straight in 354 // (no longest matching rule) 355 tempList = this.cache.get("!" + key); 356 if (tempList != null) { 357 universalList.addAll(tempList); 358 } 359 360 } else { 361 if (!ignoreBasicMatches) { 362 // ensure that all parent matches are SHORTER 363 // than rules with same level of matching. 364 // 365 // the calculations below don't work for universal 366 // matching, but we don't care because in that case 367 // this if-stmt is not entered. 368 int keyLength = key.length(); 369 if (wildcardMatchStart) { 370 --keyLength; 371 } 372 if (wildcardMatchEnd) { 373 --keyLength; 374 } else if (parentMatchEnd) { 375 --keyLength; 376 } 377 378 if (keyLength > longKeyLength) { 379 rulesList = this.cache.get(key); 380 longKey = key; 381 longKeyLength = keyLength; 382 } 383 } 384 } 385 } 386 } 387 } 388 389 390 // '*' works in practice as a default matching 391 // (this is because anything is a deeper match!) 392 if (rulesList == null) { 393 rulesList = this.cache.get("*"); 394 } 395 396 // if we've matched a basic pattern, then add to the universal list 397 if (rulesList != null) { 398 universalList.addAll(rulesList); 399 } 400 401 402 // don't filter if namespace is null 403 if (namespace != null) { 404 // remove invalid namespaces 405 Iterator<Rule> it = universalList.iterator(); 406 while (it.hasNext()) { 407 Rule rule = it.next(); 408 String ns_uri = rule.getNamespaceURI(); 409 if (ns_uri != null && !ns_uri.equals(namespace)) { 410 it.remove(); 411 } 412 } 413 } 414 415 416 // need to make sure that the collection is sort in the order 417 // of addition. We use a custom comparator for this 418 Collections.sort( 419 universalList, 420 new Comparator<Rule>() { 421 422 public int compare(Rule r1, Rule r2) throws ClassCastException { 423 // Get the entry order from the map 424 Integer i1 = order.get(r1); 425 Integer i2 = order.get(r2); 426 427 // and use that to perform the comparison 428 if (i1 == null) { 429 if (i2 == null) { 430 431 return 0; 432 433 } else { 434 435 return -1; 436 437 } 438 } else if (i2 == null) { 439 return 1; 440 } 441 442 return (i1.intValue() - i2.intValue()); 443 } 444 }); 445 446 return universalList; 447 } 448 449 /** 450 * Matching parent. 451 */ 452 private boolean parentMatch(String key, String pattern, String parentPattern) { 453 return parentPattern.endsWith(key.substring(1, key.length() - 2)); 454 } 455 456 /** 457 * Standard match. 458 * Matches the end of the pattern to the key. 459 */ 460 private boolean basicMatch(String key, String pattern) { 461 return (pattern.equals(key.substring(2)) || 462 pattern.endsWith(key.substring(1))); 463 } 464 465 /** 466 * Finds an exact ancester match for given pattern 467 */ 468 private List<Rule> findExactAncesterMatch(String parentPattern) { 469 List<Rule> matchingRules = null; 470 int lastIndex = parentPattern.length(); 471 while (lastIndex-- > 0) { 472 lastIndex = parentPattern.lastIndexOf('/', lastIndex); 473 if (lastIndex > 0) { 474 matchingRules = this.cache.get(parentPattern.substring(0, lastIndex) + "/*"); 475 if (matchingRules != null) { 476 return matchingRules; 477 } 478 } 479 } 480 return null; 481 } 482 }