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 }