- * If you are unsure how exactly a regular expression should look like, consider - * prototyping by simply trying various expressions on some test texts via - * {@link String#split(String)}. Once you are satisfied, give that regex to - * PatternAnalyzer. Also see Java Regular Expression Tutorial. - *
- * This class can be considerably faster than the "normal" Lucene tokenizers. - * It can also serve as a building block in a compound Lucene - * {@link org.apache.lucene.analysis.TokenFilter} chain. For example as in this - * stemming example: - *
- * PatternAnalyzer pat = ...
- * TokenStream tokenStream = new SnowballFilter(
- * pat.tokenStream("content", "James is running round in the woods"),
- * "English"));
- *
- *
- */
-public final class PatternAnalyzer extends Analyzer {
-
- /** "\\W+"; Divides text at non-letters (NOT Character.isLetter(c)) */
- public static final Pattern NON_WORD_PATTERN = Pattern.compile("\\W+");
-
- /** "\\s+"; Divides text at whitespaces (Character.isWhitespace(c)) */
- public static final Pattern WHITESPACE_PATTERN = Pattern.compile("\\s+");
-
- private static final CharArraySet EXTENDED_ENGLISH_STOP_WORDS =
- CharArraySet.unmodifiableSet(new CharArraySet(Version.LUCENE_CURRENT,
- Arrays.asList(
- "a", "about", "above", "across", "adj", "after", "afterwards",
- "again", "against", "albeit", "all", "almost", "alone", "along",
- "already", "also", "although", "always", "among", "amongst", "an",
- "and", "another", "any", "anyhow", "anyone", "anything",
- "anywhere", "are", "around", "as", "at", "be", "became", "because",
- "become", "becomes", "becoming", "been", "before", "beforehand",
- "behind", "being", "below", "beside", "besides", "between",
- "beyond", "both", "but", "by", "can", "cannot", "co", "could",
- "down", "during", "each", "eg", "either", "else", "elsewhere",
- "enough", "etc", "even", "ever", "every", "everyone", "everything",
- "everywhere", "except", "few", "first", "for", "former",
- "formerly", "from", "further", "had", "has", "have", "he", "hence",
- "her", "here", "hereafter", "hereby", "herein", "hereupon", "hers",
- "herself", "him", "himself", "his", "how", "however", "i", "ie", "if",
- "in", "inc", "indeed", "into", "is", "it", "its", "itself", "last",
- "latter", "latterly", "least", "less", "ltd", "many", "may", "me",
- "meanwhile", "might", "more", "moreover", "most", "mostly", "much",
- "must", "my", "myself", "namely", "neither", "never",
- "nevertheless", "next", "no", "nobody", "none", "noone", "nor",
- "not", "nothing", "now", "nowhere", "of", "off", "often", "on",
- "once one", "only", "onto", "or", "other", "others", "otherwise",
- "our", "ours", "ourselves", "out", "over", "own", "per", "perhaps",
- "rather", "s", "same", "seem", "seemed", "seeming", "seems",
- "several", "she", "should", "since", "so", "some", "somehow",
- "someone", "something", "sometime", "sometimes", "somewhere",
- "still", "such", "t", "than", "that", "the", "their", "them",
- "themselves", "then", "thence", "there", "thereafter", "thereby",
- "therefor", "therein", "thereupon", "these", "they", "this",
- "those", "though", "through", "throughout", "thru", "thus", "to",
- "together", "too", "toward", "towards", "under", "until", "up",
- "upon", "us", "very", "via", "was", "we", "well", "were", "what",
- "whatever", "whatsoever", "when", "whence", "whenever",
- "whensoever", "where", "whereafter", "whereas", "whereat",
- "whereby", "wherefrom", "wherein", "whereinto", "whereof",
- "whereon", "whereto", "whereunto", "whereupon", "wherever",
- "wherewith", "whether", "which", "whichever", "whichsoever",
- "while", "whilst", "whither", "who", "whoever", "whole", "whom",
- "whomever", "whomsoever", "whose", "whosoever", "why", "will",
- "with", "within", "without", "would", "xsubj", "xcal", "xauthor",
- "xother ", "xnote", "yet", "you", "your", "yours", "yourself",
- "yourselves"
- ), true));
-
- /**
- * A lower-casing word analyzer with English stop words (can be shared
- * freely across threads without harm); global per class loader.
- */
- public static final PatternAnalyzer DEFAULT_ANALYZER = new PatternAnalyzer(
- Version.LUCENE_CURRENT, NON_WORD_PATTERN, true, StopAnalyzer.ENGLISH_STOP_WORDS_SET);
-
- /**
- * A lower-casing word analyzer with extended English stop words
- * (can be shared freely across threads without harm); global per class
- * loader. The stop words are borrowed from
- * http://thomas.loc.gov/home/stopwords.html, see
- * http://thomas.loc.gov/home/all.about.inquery.html
- */
- public static final PatternAnalyzer EXTENDED_ANALYZER = new PatternAnalyzer(
- Version.LUCENE_CURRENT, NON_WORD_PATTERN, true, EXTENDED_ENGLISH_STOP_WORDS);
-
- private final Pattern pattern;
- private final boolean toLowerCase;
- private final Set stopWords;
-
- private final Version matchVersion;
-
- /**
- * Constructs a new instance with the given parameters.
- *
- * @param matchVersion If >= {@link Version#LUCENE_29}, StopFilter.enablePositionIncrement is set to true
- * @param pattern
- * a regular expression delimiting tokens
- * @param toLowerCase
- * if true returns tokens after applying
- * String.toLowerCase()
- * @param stopWords
- * if non-null, ignores all tokens that are contained in the
- * given stop set (after previously having applied toLowerCase()
- * if applicable). For example, created via
- * {@link StopFilter#makeStopSet(Version, String[])}and/or
- * {@link org.apache.lucene.analysis.WordlistLoader}as in
- * WordlistLoader.getWordSet(new File("samples/fulltext/stopwords.txt")
- * or other stop words
- * lists .
- */
- public PatternAnalyzer(Version matchVersion, Pattern pattern, boolean toLowerCase, Set stopWords) {
- if (pattern == null)
- throw new IllegalArgumentException("pattern must not be null");
-
- if (eqPattern(NON_WORD_PATTERN, pattern)) pattern = NON_WORD_PATTERN;
- else if (eqPattern(WHITESPACE_PATTERN, pattern)) pattern = WHITESPACE_PATTERN;
-
- if (stopWords != null && stopWords.size() == 0) stopWords = null;
-
- this.pattern = pattern;
- this.toLowerCase = toLowerCase;
- this.stopWords = stopWords;
- this.matchVersion = matchVersion;
- }
-
- /**
- * Creates a token stream that tokenizes the given string into token terms
- * (aka words).
- *
- * @param fieldName
- * the name of the field to tokenize (currently ignored).
- * @param text
- * the string to tokenize
- * @return a new token stream
- */
- public TokenStream tokenStream(String fieldName, String text) {
- // Ideally the Analyzer superclass should have a method with the same signature,
- // with a default impl that simply delegates to the StringReader flavour.
- if (text == null)
- throw new IllegalArgumentException("text must not be null");
-
- TokenStream stream;
- if (pattern == NON_WORD_PATTERN) { // fast path
- stream = new FastStringTokenizer(text, true, toLowerCase, stopWords);
- }
- else if (pattern == WHITESPACE_PATTERN) { // fast path
- stream = new FastStringTokenizer(text, false, toLowerCase, stopWords);
- }
- else {
- stream = new PatternTokenizer(text, pattern, toLowerCase);
- if (stopWords != null) stream = new StopFilter(matchVersion, stream, stopWords);
- }
-
- return stream;
- }
-
- /**
- * Creates a token stream that tokenizes all the text in the given Reader;
- * This implementation forwards to tokenStream(String, String) and is
- * less efficient than tokenStream(String, String).
- *
- * @param fieldName
- * the name of the field to tokenize (currently ignored).
- * @param reader
- * the reader delivering the text
- * @return a new token stream
- */
- @Override
- public TokenStream tokenStream(String fieldName, Reader reader) {
- if (reader instanceof FastStringReader) { // fast path
- return tokenStream(fieldName, ((FastStringReader)reader).getString());
- }
-
- try {
- String text = toString(reader);
- return tokenStream(fieldName, text);
- } catch (IOException e) {
- throw new RuntimeException(e);
- }
- }
-
- /**
- * Indicates whether some other object is "equal to" this one.
- *
- * @param other
- * the reference object with which to compare.
- * @return true if equal, false otherwise
- */
- @Override
- public boolean equals(Object other) {
- if (this == other) return true;
- if (this == DEFAULT_ANALYZER && other == EXTENDED_ANALYZER) return false;
- if (other == DEFAULT_ANALYZER && this == EXTENDED_ANALYZER) return false;
-
- if (other instanceof PatternAnalyzer) {
- PatternAnalyzer p2 = (PatternAnalyzer) other;
- return
- toLowerCase == p2.toLowerCase &&
- eqPattern(pattern, p2.pattern) &&
- eq(stopWords, p2.stopWords);
- }
- return false;
- }
-
- /**
- * Returns a hash code value for the object.
- *
- * @return the hash code.
- */
- @Override
- public int hashCode() {
- if (this == DEFAULT_ANALYZER) return -1218418418; // fast path
- if (this == EXTENDED_ANALYZER) return 1303507063; // fast path
-
- int h = 1;
- h = 31*h + pattern.pattern().hashCode();
- h = 31*h + pattern.flags();
- h = 31*h + (toLowerCase ? 1231 : 1237);
- h = 31*h + (stopWords != null ? stopWords.hashCode() : 0);
- return h;
- }
-
- /** equality where o1 and/or o2 can be null */
- private static boolean eq(Object o1, Object o2) {
- return (o1 == o2) || (o1 != null ? o1.equals(o2) : false);
- }
-
- /** assumes p1 and p2 are not null */
- private static boolean eqPattern(Pattern p1, Pattern p2) {
- return p1 == p2 || (p1.flags() == p2.flags() && p1.pattern().equals(p2.pattern()));
- }
-
- /**
- * Reads until end-of-stream and returns all read chars, finally closes the stream.
- *
- * @param input the input stream
- * @throws IOException if an I/O error occurs while reading the stream
- */
- private static String toString(Reader input) throws IOException {
- try {
- int len = 256;
- char[] buffer = new char[len];
- char[] output = new char[len];
-
- len = 0;
- int n;
- while ((n = input.read(buffer)) >= 0) {
- if (len + n > output.length) { // grow capacity
- char[] tmp = new char[Math.max(output.length << 1, len + n)];
- System.arraycopy(output, 0, tmp, 0, len);
- System.arraycopy(buffer, 0, tmp, len, n);
- buffer = output; // use larger buffer for future larger bulk reads
- output = tmp;
- } else {
- System.arraycopy(buffer, 0, output, len, n);
- }
- len += n;
- }
-
- return new String(output, 0, len);
- } finally {
- input.close();
- }
- }
-
-
- ///////////////////////////////////////////////////////////////////////////////
- // Nested classes:
- ///////////////////////////////////////////////////////////////////////////////
- /**
- * The work horse; performance isn't fantastic, but it's not nearly as bad
- * as one might think - kudos to the Sun regex developers.
- */
- private static final class PatternTokenizer extends TokenStream {
-
- private final String str;
- private final boolean toLowerCase;
- private Matcher matcher;
- private int pos = 0;
- private static final Locale locale = Locale.getDefault();
- private final CharTermAttribute termAtt = addAttribute(CharTermAttribute.class);
- private final OffsetAttribute offsetAtt = addAttribute(OffsetAttribute.class);
-
- public PatternTokenizer(String str, Pattern pattern, boolean toLowerCase) {
- this.str = str;
- this.matcher = pattern.matcher(str);
- this.toLowerCase = toLowerCase;
- }
-
- @Override
- public final boolean incrementToken() {
- if (matcher == null) return false;
- clearAttributes();
- while (true) { // loop takes care of leading and trailing boundary cases
- int start = pos;
- int end;
- boolean isMatch = matcher.find();
- if (isMatch) {
- end = matcher.start();
- pos = matcher.end();
- } else {
- end = str.length();
- matcher = null; // we're finished
- }
-
- if (start != end) { // non-empty match (header/trailer)
- String text = str.substring(start, end);
- if (toLowerCase) text = text.toLowerCase(locale);
- termAtt.setEmpty().append(text);
- offsetAtt.setOffset(start, end);
- return true;
- }
- if (!isMatch) return false;
- }
- }
-
- @Override
- public final void end() {
- // set final offset
- final int finalOffset = str.length();
- this.offsetAtt.setOffset(finalOffset, finalOffset);
- }
- }
-
-
- ///////////////////////////////////////////////////////////////////////////////
- // Nested classes:
- ///////////////////////////////////////////////////////////////////////////////
- /**
- * Special-case class for best performance in common cases; this class is
- * otherwise unnecessary.
- */
- private static final class FastStringTokenizer extends TokenStream {
-
- private final String str;
- private int pos;
- private final boolean isLetter;
- private final boolean toLowerCase;
- private final Set stopWords;
- private static final Locale locale = Locale.getDefault();
- private final CharTermAttribute termAtt = addAttribute(CharTermAttribute.class);
- private final OffsetAttribute offsetAtt = addAttribute(OffsetAttribute.class);
-
- public FastStringTokenizer(String str, boolean isLetter, boolean toLowerCase, Set stopWords) {
- this.str = str;
- this.isLetter = isLetter;
- this.toLowerCase = toLowerCase;
- this.stopWords = stopWords;
- }
-
- @Override
- public boolean incrementToken() {
- clearAttributes();
- // cache loop instance vars (performance)
- String s = str;
- int len = s.length();
- int i = pos;
- boolean letter = isLetter;
-
- int start = 0;
- String text;
- do {
- // find beginning of token
- text = null;
- while (i < len && !isTokenChar(s.charAt(i), letter)) {
- i++;
- }
-
- if (i < len) { // found beginning; now find end of token
- start = i;
- while (i < len && isTokenChar(s.charAt(i), letter)) {
- i++;
- }
-
- text = s.substring(start, i);
- if (toLowerCase) text = text.toLowerCase(locale);
-// if (toLowerCase) {
-//// use next line once JDK 1.5 String.toLowerCase() performance regression is fixed
-//// see http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6265809
-// text = s.substring(start, i).toLowerCase();
-//// char[] chars = new char[i-start];
-//// for (int j=start; j < i; j++) chars[j-start] = Character.toLowerCase(s.charAt(j));
-//// text = new String(chars);
-// } else {
-// text = s.substring(start, i);
-// }
- }
- } while (text != null && isStopWord(text));
-
- pos = i;
- if (text == null)
- {
- return false;
- }
- termAtt.setEmpty().append(text);
- offsetAtt.setOffset(start, i);
- return true;
- }
-
- @Override
- public final void end() {
- // set final offset
- final int finalOffset = str.length();
- this.offsetAtt.setOffset(finalOffset, finalOffset);
- }
-
- private boolean isTokenChar(char c, boolean isLetter) {
- return isLetter ? Character.isLetter(c) : !Character.isWhitespace(c);
- }
-
- private boolean isStopWord(String text) {
- return stopWords != null && stopWords.contains(text);
- }
-
- }
-
-
- ///////////////////////////////////////////////////////////////////////////////
- // Nested classes:
- ///////////////////////////////////////////////////////////////////////////////
- /**
- * A StringReader that exposes it's contained string for fast direct access.
- * Might make sense to generalize this to CharSequence and make it public?
- */
- static final class FastStringReader extends StringReader {
-
- private final String s;
-
- FastStringReader(String s) {
- super(s);
- this.s = s;
- }
-
- String getString() {
- return s;
- }
- }
-
-}