001    /**
002     * Copyright (c) 2000-present Liferay, Inc. All rights reserved.
003     *
004     * This library is free software; you can redistribute it and/or modify it under
005     * the terms of the GNU Lesser General Public License as published by the Free
006     * Software Foundation; either version 2.1 of the License, or (at your option)
007     * any later version.
008     *
009     * This library is distributed in the hope that it will be useful, but WITHOUT
010     * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
011     * FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
012     * details.
013     */
014    
015    package com.liferay.portal.expression;
016    
017    import java.util.ArrayList;
018    import java.util.Collections;
019    import java.util.List;
020    import java.util.regex.Matcher;
021    import java.util.regex.Pattern;
022    
023    /**
024     * @author Marcellus Tavares
025     */
026    public class VariableNamesExtractor {
027    
028            public List<String> extract(String expressionString) {
029                    if (expressionString == null) {
030                            return Collections.emptyList();
031                    }
032    
033                    List<String> variableNames = new ArrayList<String>();
034    
035                    Matcher matcher = _pattern.matcher(expressionString);
036    
037                    while (matcher.find()) {
038                            variableNames.add(matcher.group(1));
039                    }
040    
041                    return variableNames;
042            }
043    
044            private static final Pattern _pattern = Pattern.compile(
045                    "\\b([a-zA-Z]+[\\w\\._]*)(?!\\()\\b", Pattern.MULTILINE);
046    
047    }