-This module exposes functionality from -ICU to Apache Lucene. ICU4J is a Java -library that enhances Java's internationalization support by improving -performance, keeping current with the Unicode Standard, and providing richer -APIs. This module exposes the following functionality: -
--Text Segmentation (Tokenization) divides document and query text into index terms -(typically words). Unicode provides special properties and rules so that this can -be done in a manner that works well with most languages. -
--Text Segmentation implements the word segmentation specified in -Unicode Text Segmentation. -Additionally the algorithm can be tailored based on writing system, for example -text in the Thai script is automatically delegated to a dictionary-based segmentation -algorithm. -
-- /** - * This tokenizer will work well in general for most languages. - */ - Tokenizer tokenizer = new ICUTokenizer(reader); --
- ICUCollationKeyFilter
- converts each token into its binary CollationKey using the
- provided Collator, and then encode the CollationKey
- as a String using
- {@link org.apache.lucene.util.IndexableBinaryStringTools}, to allow it to be
- stored as an index term.
-
- ICUCollationKeyFilter depends on ICU4J 4.4 to produce the
- CollationKeys. icu4j-4.4.jar
- is included in Lucene's Subversion repository at contrib/icu/lib/.
-
- Collator collator = Collator.getInstance(new Locale("ar"));
- ICUCollationKeyAnalyzer analyzer = new ICUCollationKeyAnalyzer(collator);
- RAMDirectory ramDir = new RAMDirectory();
- IndexWriter writer = new IndexWriter
- (ramDir, analyzer, true, IndexWriter.MaxFieldLength.LIMITED);
- Document doc = new Document();
- doc.add(new Field("content", "\u0633\u0627\u0628",
- Field.Store.YES, Field.Index.ANALYZED));
- writer.addDocument(doc);
- writer.close();
- IndexSearcher is = new IndexSearcher(ramDir, true);
-
- // The AnalyzingQueryParser in Lucene's contrib allows terms in range queries
- // to be passed through an analyzer - Lucene's standard QueryParser does not
- // allow this.
- AnalyzingQueryParser aqp = new AnalyzingQueryParser("content", analyzer);
- aqp.setLowercaseExpandedTerms(false);
-
- // Unicode order would include U+0633 in [ U+062F - U+0698 ], but Farsi
- // orders the U+0698 character before the U+0633 character, so the single
- // indexed Term above should NOT be returned by a ConstantScoreRangeQuery
- // with a Farsi Collator (or an Arabic one for the case when Farsi is not
- // supported).
- ScoreDoc[] result
- = is.search(aqp.parse("[ \u062F TO \u0698 ]"), null, 1000).scoreDocs;
- assertEquals("The index Term should not be included.", 0, result.length);
-
-
-
- Analyzer analyzer
- = new ICUCollationKeyAnalyzer(Collator.getInstance(new Locale("da", "dk")));
- RAMDirectory indexStore = new RAMDirectory();
- IndexWriter writer = new IndexWriter
- (indexStore, analyzer, true, IndexWriter.MaxFieldLength.LIMITED);
- String[] tracer = new String[] { "A", "B", "C", "D", "E" };
- String[] data = new String[] { "HAT", "HUT", "H\u00C5T", "H\u00D8T", "HOT" };
- String[] sortedTracerOrder = new String[] { "A", "E", "B", "D", "C" };
- for (int i = 0 ; i < data.length ; ++i) {
- Document doc = new Document();
- doc.add(new Field("tracer", tracer[i], Field.Store.YES, Field.Index.NO));
- doc.add(new Field("contents", data[i], Field.Store.NO, Field.Index.ANALYZED));
- writer.addDocument(doc);
- }
- writer.close();
- Searcher searcher = new IndexSearcher(indexStore, true);
- Sort sort = new Sort();
- sort.setSort(new SortField("contents", SortField.STRING));
- Query query = new MatchAllDocsQuery();
- ScoreDoc[] result = searcher.search(query, null, 1000, sort).scoreDocs;
- for (int i = 0 ; i < result.length ; ++i) {
- Document doc = searcher.doc(result[i].doc);
- assertEquals(sortedTracerOrder[i], doc.getValues("tracer")[0]);
- }
-
-
-
- Collator collator = Collator.getInstance(new Locale("tr", "TR"));
- collator.setStrength(Collator.PRIMARY);
- Analyzer analyzer = new ICUCollationKeyAnalyzer(collator);
- RAMDirectory ramDir = new RAMDirectory();
- IndexWriter writer = new IndexWriter
- (ramDir, analyzer, true, IndexWriter.MaxFieldLength.LIMITED);
- Document doc = new Document();
- doc.add(new Field("contents", "DIGY", Field.Store.NO, Field.Index.ANALYZED));
- writer.addDocument(doc);
- writer.close();
- IndexSearcher is = new IndexSearcher(ramDir, true);
- QueryParser parser = new QueryParser("contents", analyzer);
- Query query = parser.parse("d\u0131gy"); // U+0131: dotless i
- ScoreDoc[] result = is.search(query, null, 1000).scoreDocs;
- assertEquals("The index Term should be included.", 1, result.length);
-
-
-
- WARNING: Make sure you use exactly the same
- Collator at index and query time -- CollationKeys
- are only comparable when produced by
- the same Collator. Since {@link java.text.RuleBasedCollator}s
- are not independently versioned, it is unsafe to search against stored
- CollationKeys unless the following are exactly the same (best
- practice is to store this information with the index and check that they
- remain the same at query time):
-
- ICUCollationKeyFilter uses ICU4J's Collator, which
- makes its version available, thus allowing collation to be versioned
- independently from the JVM. ICUCollationKeyFilter is also
- significantly faster and generates significantly shorter keys than
- CollationKeyFilter. See
- http://site.icu-project.org/charts/collation-icu4j-sun for key
- generation timing and key length comparisons between ICU4J and
- java.text.Collator over several languages.
-
- CollationKeys generated by java.text.Collators are
- not compatible with those those generated by ICU Collators. Specifically, if
- you use CollationKeyFilter to generate index terms, do not use
- ICUCollationKeyFilter on the query side, or vice versa.
-
- ICUNormalizer2Filter normalizes term text to a
- Unicode Normalization Form, so
- that equivalent
- forms are standardized to a unique form.
-
- /** - * Normalizer2 objects are unmodifiable and immutable. - */ - Normalizer2 normalizer = Normalizer2.getInstance(null, "nfc", Normalizer2.Mode.COMPOSE); - /** - * This filter will normalize to NFC. - */ - TokenStream tokenstream = new ICUNormalizer2Filter(tokenizer, normalizer); --
-Default caseless matching, or case-folding is more than just conversion to -lowercase. For example, it handles cases such as the Greek sigma, so that -"ÎάÏοÏ" and "ÎÎΪÎΣ" will match correctly. -
--Case-folding is still only an approximation of the language-specific rules -governing case. If the specific language is known, consider using -ICUCollationKeyFilter and indexing collation keys instead. This implementation -performs the "full" case-folding specified in the Unicode standard, and this -may change the length of the term. For example, the German à is case-folded -to the string 'ss'. -
--Case folding is related to normalization, and as such is coupled with it in -this integration. To perform case-folding, you use normalization with the form -"nfkc_cf" (which is the default). -
-- /** - * This filter will case-fold and normalize to NFKC. - */ - TokenStream tokenstream = new ICUNormalizer2Filter(tokenizer); --
-Search term folding removes distinctions (such as accent marks) between -similar characters. It is useful for a fuzzy or loose search. -
--Search term folding implements many of the foldings specified in -Character Foldings -as a special normalization form. This folding applies NFKC, Case Folding, and -many character foldings recursively. -
-- /** - * This filter will case-fold, remove accents and other distinctions, and - * normalize to NFKC. - */ - TokenStream tokenstream = new ICUFoldingFilter(tokenizer); --
-ICU provides text-transformation functionality via its Transliteration API. This allows -you to transform text in a variety of ways, taking context into account. -
--For more information, see the -User's Guide -and -Rule Tutorial. -
-
- /**
- * This filter will map Traditional Chinese to Simplified Chinese
- */
- TokenStream tokenstream = new ICUTransformFilter(tokenizer, Transliterator.getInstance("Traditional-Simplified"));
-
-
- /**
- * This filter will map Serbian Cyrillic to Serbian Latin according to BGN rules
- */
- TokenStream tokenstream = new ICUTransformFilter(tokenizer, Transliterator.getInstance("Serbian-Latin/BGN"));
-
--This module exists to provide up-to-date Unicode functionality that supports -the most recent version of Unicode (currently 6.0). However, some users who wish -for stronger backwards compatibility can restrict -{@link org.apache.lucene.analysis.icu.ICUNormalizer2Filter} to operate on only -a specific Unicode Version by using a {@link com.ibm.icu.text.FilteredNormalizer2}. -
-
- /**
- * This filter will do NFC normalization, but will ignore any characters that
- * did not exist as of Unicode 5.0. Because of the normalization stability policy
- * of Unicode, this is an easy way to force normalization to a specific version.
- */
- Normalizer2 normalizer = Normalizer2.getInstance(null, "nfc", Normalizer2.Mode.COMPOSE);
- UnicodeSet set = new UnicodeSet("[:age=5.0:]");
- // see FilteredNormalizer2 docs, the set should be frozen or performance will suffer
- set.freeze();
- FilteredNormalizer2 unicode50 = new FilteredNormalizer2(normalizer, set);
- TokenStream tokenstream = new ICUNormalizer2Filter(tokenizer, unicode50);
-
-
-