com.xceptance.common.util.RegExUtils Maven / Gradle / Ivy
Show all versions of xlt Show documentation
/*
* Copyright (c) 2005-2022 Xceptance Software Technologies GmbH
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.xceptance.common.util;
import java.util.ArrayList;
import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import java.util.regex.PatternSyntaxException;
import org.apache.commons.lang3.StringUtils;
import com.xceptance.common.collection.ConcurrentLRUCache;
/**
* The RegExUtils class provides some helper functions to make dealing with regular expressions easier.
*
* Note that regular expressions passed in as a string are compiled with the Pattern.DOTALL and Pattern.MULTILINE flags
* set. If this does not fit your needs, use the methods that take a compiled pattern and provide the appropriate
* pattern object yourself. Furthermore, to improve performance regex strings - once compiled to pattern objects - are
* cached internally for later re-use.
*
* @author Jörg Werner (Xceptance Software Technologies GmbH)
*/
public final class RegExUtils
{
/**
* Maps regular expression strings to their compiled equivalents.
*/
private static final ConcurrentLRUCache patternCache = new ConcurrentLRUCache(5003);
/**
* Maps regular expression evaluation results to the string to save operations
*/
private static final ConcurrentLRUCache resultCache = new ConcurrentLRUCache(1001);
/**
* Default constructor. Declared private to prevent external instantiation.
*/
private RegExUtils()
{
// Nothing to do
}
/**
* Returns how many sub strings of the specified input string match the passed pattern.
*
* @param s
* the input string
* @param pattern
* the pattern to match
* @return the number of matches
*/
public static int getMatchingCount(final String s, final Pattern pattern)
{
int count = 0;
final Matcher matcher = pattern.matcher(s);
while (matcher.find())
{
count++;
}
return count;
}
/**
* Returns how many sub strings of the specified input string match the passed pattern.
*
* @param s
* the input string
* @param regex
* the pattern to match
* @return the number of matches
*/
public static int getMatchingCount(final String s, final String regex)
{
return getMatchingCount(s, getPattern(regex));
}
/**
* Returns the compiled equivalent of the passed regular expression string. This method tries to improve performance
* by caching the compiled pattern, so subsequent calls with the same regex will return the previously cached
* pattern. The regex will be compiled with DOTALL and MULTILINE.
*
* @param regex
* the regular expression string
* @return the corresponding pattern object
*/
public static Pattern getPattern(final String regex)
{
return getPattern(regex, Pattern.DOTALL | Pattern.MULTILINE);
}
/**
* Returns the compiled equivalent of the passed regular expression string. This method tries to improve performance
* by caching the compiled pattern, so subsequent calls with the same regex will return the previously cached
* pattern.
*
* @param regex
* the regular expression string
* @param flags
* global flags to be used when compiling the regular expression
* @throws PatternSyntaxException
* if the regular expression is invalid
* @return the corresponding pattern object
*/
public static Pattern getPattern(final String regex, final int flags)
{
// cache string to take flags into account
final CacheKey cacheKey = new CacheKey(regex, flags);
Pattern pattern = patternCache.get(cacheKey);
if (pattern == null)
{
pattern = Pattern.compile(regex, flags);
patternCache.put(cacheKey, pattern);
}
return pattern;
}
/**
* Indicates whether there is at least one sub string of the specified input string that matches the passed pattern.
*
* @param s
* the input string
* @param pattern
* the pattern to match
* @return true if the input matches the pattern
*/
public static boolean isMatching(final String s, final Pattern pattern)
{
final Matcher matcher = pattern.matcher(s);
return matcher.find();
}
/**
* Indicates whether there is at least one sub string of the specified input string that matches the passed pattern.
*
* @param s
* the input string
* @param regex
* the pattern to match
* @return whether the input matches the pattern
*/
public static boolean isMatching(final String s, final String regex)
{
return isMatching(s, getPattern(regex));
}
/**
* Returns all sub strings of the specified input string that match the passed pattern.
*
* @param s
* the input string
* @param pattern
* the pattern to match
* @return a list of matching sub strings
*/
public static List getAllMatches(final String s, final Pattern pattern)
{
return getAllMatches(s, pattern, 0);
}
/**
* Finds all sub strings of the specified input string that match the passed pattern and, for each sub string,
* returns the value of the matching group with the given index.
*
* @param s
* the input string
* @param pattern
* the pattern to match
* @param matchingGroupIndex
* the matching group in question
* @return a list with the values of the specified matching group
*/
public static List getAllMatches(final String s, final Pattern pattern, final int matchingGroupIndex)
{
final List values = new ArrayList();
final Matcher matcher = pattern.matcher(s);
while (matcher.find())
{
final String value = matcher.group(matchingGroupIndex);
values.add(value);
}
return values;
}
/**
* Returns all sub strings of the specified input string that match the passed pattern.
*
* @param s
* the input string
* @param regex
* the pattern to match
* @return a list of matching sub strings
*/
public static List getAllMatches(final String s, final String regex)
{
return getAllMatches(s, getPattern(regex), 0);
}
/**
* Finds all sub strings of the specified input string that match the passed pattern and, for each sub string,
* returns the value of the matching group with the given index.
*
* @param s
* the input string
* @param regex
* the regular expression to match
* @param matchingGroupIndex
* the matching group in question
* @return a list with the values of the specified matching group
*/
public static List getAllMatches(final String s, final String regex, final int matchingGroupIndex)
{
return getAllMatches(s, getPattern(regex), matchingGroupIndex);
}
/**
* Returns the first sub string of the specified input string that matches the passed pattern.
*
* @param s
* the input string
* @param pattern
* the pattern to match
* @return the first matching sub string
*/
public static String getFirstMatch(final String s, final Pattern pattern)
{
return getFirstMatch(s, pattern, 0);
}
/**
* Finds the first sub string of the specified input string that matches the passed pattern and returns the value of
* the matching group with the given index.
*
* @param s
* the input string
* @param pattern
* the pattern to match
* @param matchingGroupIndex
* the matching group in question
* @return the value of the specified matching group
*/
public static String getFirstMatch(final String s, final Pattern pattern, final int matchingGroupIndex)
{
String value = null;
final Matcher matcher = pattern.matcher(s);
if (matcher.find())
{
value = matcher.group(matchingGroupIndex);
}
return value;
}
/**
* Returns the first sub string of the specified input string that matches the passed pattern.
*
* @param s
* the input string
* @param regex
* the pattern to match
* @return the first matching sub string
*/
public static String getFirstMatch(final String s, final String regex)
{
return getFirstMatch(s, getPattern(regex));
}
/**
* Finds the first sub string of the specified input string that matches the passed pattern and returns the value of
* the matching group with the given index.
*
* @param s
* the input string
* @param regex
* the pattern to match
* @param matchingGroupIndex
* the matching group in question
* @return the value of the specified matching group
*/
public static String getFirstMatch(final String s, final String regex, final int matchingGroupIndex)
{
return getFirstMatch(s, getPattern(regex), matchingGroupIndex);
}
/**
* Finds all matches for the given regular expression in the given string s and replaces them with the given
* replacement string. Similar to {@link String#replaceAll(String, String)}, but the pattern compiled from the
* regular expression is cached internally.
*
* @param s
* the input string
* @param regex
* the regular expression to be matched
* @param replacement
* the replacement string
* @return the modified input string
*/
public static String replaceAll(final String s, final String regex, final String replacement)
{
final Pattern pattern = getPattern(regex);
final Matcher matcher = pattern.matcher(s);
return matcher.replaceAll(replacement);
}
/**
* Returns the given string after it has been escaped.
*
* @param s
* the string to be escaped
* @return escaped string
*/
public static String escape(final String s)
{
// parameter validation
if (s == null || s.length() == 0)
{
return s;
}
// check the cache to save computation
String cachedVal = resultCache.get(s);
// cache miss
if (cachedVal == null)
{
// get quoted regex and fill cache
cachedVal = Pattern.quote(s);
resultCache.put(s, cachedVal);
}
return cachedVal;
}
/**
* Returns the number of capturing groups defined by the given regular expression.
*
* @param pattern
* the regular expression
* @return number of capturing groups or -1 if passed regular expression is empty (or null)
*/
public static int getCaptureGroupCount(String pattern)
{
if (pattern == null || pattern.length() == 0)
{
return -1;
}
// 1st step: Remove all escaped chars.
pattern = replaceAll(pattern, "\\\\.", "");
// 2nd step: Remove all character classes.
pattern = replaceAll(pattern, "\\[[^\\]]+\\]", "");
// 3rd step. Now count all left parentheses that are not followed by a question mark.
return getMatchingCount(pattern, "\\((?![?])");
}
/**
* Helper to get the caching right
*
* @author rschwietzke
*/
static class CacheKey
{
private final String pattern;
private final int flags;
private final int hashCode;
public CacheKey(final String pattern, final int flags)
{
super();
this.pattern = pattern;
this.flags = flags;
// Since CacheKey is immutable compute hash code initially for better performance
final int prime = 31;
int result = 1;
result = prime * result + flags;
result = prime * result + ((pattern == null) ? 0 : pattern.hashCode());
hashCode = result;
}
@Override
public int hashCode()
{
return hashCode;
}
@Override
public boolean equals(final Object obj)
{
if (this == obj)
{
return true;
}
if (obj == null)
{
return false;
}
if (getClass() != obj.getClass())
{
return false;
}
final CacheKey other = (CacheKey) obj;
if (flags != other.flags)
{
return false;
}
if (pattern == null)
{
if (other.pattern != null)
{
return false;
}
}
else if (!pattern.equals(other.pattern))
{
return false;
}
return true;
}
}
/**
* Remove all matchings for the given regular expression from the given string. This method makes use of pattern
* caching.
*
* @param s
* the string to parse
* @param regex
* the regular expression to match
* @return the process result
*/
public static String removeAll(final String s, final String regex)
{
return removeAll(s, regex, 0);
}
/**
* Remove the given group from the regular expression's matching. Note, not the group is removed from the whole
* string. This method makes use of pattern caching.
*
* Examples:
*
*
*
* Sample text
* Regular Expression
* Group
* Result
* Comment
*
*
*
* FooBoo
* F(o)o
* 0
* Boo
* Remove completely
*
*
* FooBooFooBoo
* F(o)o
* 1
* FoBooFoBoo
* 'o' is not removed from complete string but from current matching
*
*
*
*
* @param s
* string to parse
* @param regex
* regular expression to match
* @param group
* the regular expression's group to remove from the string
* @return the process result
*/
public static String removeAll(final String s, final String regex, final int group)
{
// is there something to do?
if (StringUtils.isEmpty(s) || StringUtils.isEmpty(regex))
{
return s;
}
final StringBuilder result = new StringBuilder(s);
// parse the string with the (cached) matcher
final Matcher matcher = getPattern(regex).matcher(s);
int matchIndex = 0;
while (matcher.find())
{
// get the complete matching as well as the desired group
final String matching = matcher.group(0);
final String groupMatching = matcher.group(group);
// stop , if no matching for this group
if(StringUtils.isEmpty(groupMatching))
{
break;
}
// remove the group from the matching
final String modifiedMatching = StringUtils.substringBefore(matching, groupMatching) +
StringUtils.substringAfter(matching, groupMatching);
// OK, it's a change. So build the new result
result.replace(matcher.start() - matchIndex, matcher.end() - matchIndex, modifiedMatching);
matchIndex += groupMatching.length();
// and position the matcher behind the last matching
matcher.region(matcher.end(), s.length());
}
return result.toString();
}
}