001 /* $Id: SimpleRegexMatcher.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 package org.apache.commons.digester;
020
021 import org.apache.commons.logging.Log;
022 import org.apache.commons.logging.LogFactory;
023
024 /**
025 * <p>Simple regex pattern matching algorithm.</p>
026 *
027 * <p>This uses just two wildcards:
028 * <ul>
029 * <li><code>*</code> matches any sequence of none, one or more characters
030 * <li><code>?</code> matches any one character
031 * </ul>
032 * Escaping these wildcards is not supported .</p>
033 *
034 * @since 1.5
035 */
036
037 public class SimpleRegexMatcher extends RegexMatcher {
038
039 // --------------------------------------------------------- Fields
040
041 /** Default log (class wide) */
042 private static final Log baseLog = LogFactory.getLog(SimpleRegexMatcher.class);
043
044 /** Custom log (can be set per object) */
045 private Log log = baseLog;
046
047 // --------------------------------------------------------- Properties
048
049 /**
050 * Gets the <code>Log</code> implementation.
051 */
052 public Log getLog() {
053 return log;
054 }
055
056 /**
057 * Sets the current <code>Log</code> implementation used by this class.
058 */
059 public void setLog(Log log) {
060 this.log = log;
061 }
062
063 // --------------------------------------------------------- Public Methods
064
065 /**
066 * Matches using simple regex algorithm.
067 *
068 *
069 * @param basePattern the standard digester path representing the element
070 * @param regexPattern the regex pattern the path will be tested against
071 * @return true if the given pattern matches the given path
072 */
073 public boolean match(String basePattern, String regexPattern) {
074 // check for nulls
075 if (basePattern == null || regexPattern == null) {
076 return false;
077 }
078 return match(basePattern, regexPattern, 0, 0);
079 }
080
081 // --------------------------------------------------------- Implementations Methods
082
083 /**
084 * Implementation of regex matching algorithm.
085 * This calls itself recursively.
086 */
087 private boolean match(String basePattern, String regexPattern, int baseAt, int regexAt) {
088 if (log.isTraceEnabled()) {
089 log.trace("Base: " + basePattern);
090 log.trace("Regex: " + regexPattern);
091 log.trace("Base@" + baseAt);
092 log.trace("Regex@" + regexAt);
093 }
094
095 // check bounds
096 if (regexAt >= regexPattern.length()) {
097 // maybe we've got a match
098 if (baseAt >= basePattern.length()) {
099 // ok!
100 return true;
101 }
102 // run out early
103 return false;
104
105 } else {
106 if (baseAt >= basePattern.length()) {
107 // run out early
108 return false;
109 }
110 }
111
112 // ok both within bounds
113 char regexCurrent = regexPattern.charAt(regexAt);
114 switch (regexCurrent) {
115 case '*':
116 // this is the tricky case
117 // check for terminal
118 if (++regexAt >= regexPattern.length()) {
119 // this matches anything let - so return true
120 return true;
121 }
122 // go through every subsequent apperance of the next character
123 // and so if the rest of the regex matches
124 char nextRegex = regexPattern.charAt(regexAt);
125 if (log.isTraceEnabled()) {
126 log.trace("Searching for next '" + nextRegex + "' char");
127 }
128 int nextMatch = basePattern.indexOf(nextRegex, baseAt);
129 while (nextMatch != -1) {
130 if (log.isTraceEnabled()) {
131 log.trace("Trying '*' match@" + nextMatch);
132 }
133 if (match(basePattern, regexPattern, nextMatch, regexAt)) {
134 return true;
135 }
136 nextMatch = basePattern.indexOf(nextRegex, nextMatch + 1);
137 }
138 log.trace("No matches found.");
139 return false;
140
141 case '?':
142 // this matches anything
143 return match(basePattern, regexPattern, ++baseAt, ++regexAt);
144
145 default:
146 if (log.isTraceEnabled()) {
147 log.trace("Camparing " + regexCurrent + " to " + basePattern.charAt(baseAt));
148 }
149 if (regexCurrent == basePattern.charAt(baseAt)) {
150 // still got more to go
151 return match(basePattern, regexPattern, ++baseAt, ++regexAt);
152 }
153 return false;
154 }
155 }
156 }