pylucene 3.5.0-3

[pylucene.git] / lucene-java-3.5.0 / lucene / contrib / icu / src / java / org / apache / lucene / collation / ICUCollationKeyAnalyzer.java

diff --git a/lucene-java-3.5.0/lucene/contrib/icu/src/java/org/apache/lucene/collation/ICUCollationKeyAnalyzer.java b/lucene-java-3.5.0/lucene/contrib/icu/src/java/org/apache/lucene/collation/ICUCollationKeyAnalyzer.java
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+package org.apache.lucene.collation;
+
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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.
+ */
+
+
+import com.ibm.icu.text.Collator;
+import org.apache.lucene.analysis.Analyzer;
+import org.apache.lucene.analysis.TokenStream;
+import org.apache.lucene.analysis.KeywordTokenizer;
+import org.apache.lucene.analysis.Tokenizer;
+
+import org.apache.lucene.collation.CollationKeyAnalyzer; // javadocs
+
+import java.io.Reader;
+import java.io.IOException;
+
+
+/**
+ * <p>
+ *   Filters {@link KeywordTokenizer} with {@link ICUCollationKeyFilter}.
+ * <p>
+ *   Converts the token into its {@link com.ibm.icu.text.CollationKey}, and
+ *   then encodes the CollationKey with 
+ *   {@link org.apache.lucene.util.IndexableBinaryStringTools}, to allow it to
+ *   be stored as an index term.
+ * </p>
+ * <p>
+ *   <strong>WARNING:</strong> Make sure you use exactly the same Collator at
+ *   index and query time -- CollationKeys are only comparable when produced by
+ *   the same Collator.  {@link com.ibm.icu.text.RuleBasedCollator}s are 
+ *   independently versioned, so it is safe to search against stored
+ *   CollationKeys if 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):
+ * </p>
+ * <ol>
+ *   <li>
+ *     Collator version - see {@link Collator#getVersion()}
+ *   </li>
+ *   <li>
+ *     The collation strength used - see {@link Collator#setStrength(int)}
+ *   </li>
+ * </ol> 
+ * <p>
+ *   CollationKeys generated by ICU Collators are not compatible with those
+ *   generated by java.text.Collators.  Specifically, if you use 
+ *   ICUCollationKeyAnalyzer to generate index terms, do not use 
+ *   {@link CollationKeyAnalyzer} on the query side, or vice versa.
+ * </p>
+ * <p>
+ *   ICUCollationKeyAnalyzer is significantly faster and generates significantly
+ *   shorter keys than CollationKeyAnalyzer.  See
+ *   <a href="http://site.icu-project.org/charts/collation-icu4j-sun"
+ *   >http://site.icu-project.org/charts/collation-icu4j-sun</a> for key
+ *   generation timing and key length comparisons between ICU4J and
+ *   java.text.Collator over several languages.
+ * </p>
+ */
+public final class ICUCollationKeyAnalyzer extends Analyzer {
+  private Collator collator;
+
+  public ICUCollationKeyAnalyzer(Collator collator) {
+    this.collator = collator;
+  }
+
+  @Override
+  public TokenStream tokenStream(String fieldName, Reader reader) {
+    TokenStream result = new KeywordTokenizer(reader);
+    result = new ICUCollationKeyFilter(result, collator);
+    return result;
+  }
+  
+  private class SavedStreams {
+    Tokenizer source;
+    TokenStream result;
+  }
+  
+  @Override
+  public TokenStream reusableTokenStream(String fieldName, Reader reader) 
+    throws IOException {
+    
+    SavedStreams streams = (SavedStreams)getPreviousTokenStream();
+    if (streams == null) {
+      streams = new SavedStreams();
+      streams.source = new KeywordTokenizer(reader);
+      streams.result = new ICUCollationKeyFilter(streams.source, collator);
+      setPreviousTokenStream(streams);
+    } else {
+      streams.source.reset(reader);
+    }
+    return streams.result;
+  }
+}