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package org.apache.lucene.facet.enhancements.association;
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import java.util.HashSet;
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import org.apache.lucene.analysis.TokenStream;
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import org.apache.lucene.facet.enhancements.CategoryEnhancement;
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import org.apache.lucene.facet.enhancements.params.EnhancementsIndexingParams;
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import org.apache.lucene.facet.index.attributes.CategoryAttribute;
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import org.apache.lucene.facet.index.attributes.CategoryProperty;
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import org.apache.lucene.facet.index.streaming.CategoryListTokenizer;
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import org.apache.lucene.facet.taxonomy.TaxonomyWriter;
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import org.apache.lucene.util.Vint8;
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import org.apache.lucene.util.Vint8.Position;
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership.
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* The ASF licenses this file to You under the Apache License, Version 2.0
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* (the "License"); you may not use this file except in compliance with
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* the License. You may obtain a copy of the License at
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* http://www.apache.org/licenses/LICENSE-2.0
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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* A {@link CategoryEnhancement} for adding associations data to the index
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* (categories with {@link AssociationProperty}s).
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* @lucene.experimental
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public class AssociationEnhancement implements CategoryEnhancement {
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static final String CATEGORY_LIST_TERM_TEXT = "CATEGORY_ASSOCIATION_LIST";
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/** Property Classes which extend AssociationProperty */
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private static final HashSet<Class<? extends CategoryProperty>> ASSOCIATION_PROPERTY_CLASSES;
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/** Property Classes which do not extend AssociationProperty */
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private static final HashSet<Class<? extends CategoryProperty>> NON_ASSOCIATION_PROPERTY_CLASSES;
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ASSOCIATION_PROPERTY_CLASSES = new HashSet<Class<? extends CategoryProperty>>();
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NON_ASSOCIATION_PROPERTY_CLASSES = new HashSet<Class<? extends CategoryProperty>>();
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* For a given class which extends a CategoryProperty, answers whether it is
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* an instance of AssociationProperty (AP) or not. <br>
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* This method is a cheaper replacement for a call to
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* <code>instanceof</code>. It has two HashSets - one for classes which are
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* an extension to AP and one for the classes which are not. Whenever a
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* property class is introduced:
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* <li>if it is known as a property class extending AP (contained in the
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* validHashSet)- returns true</li>
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* <li>if it is known as a property class NOT extending AP - returns false</li>
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* If it was not matched against both sets, it calls 'instanceof' to find
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* out if it extends AP, puts it in the matching Set and returning true or
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* false accordingly</li>
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* NOTE: 'instanceof' is only called once per a Class (not instance) of a
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* property. And as there are few properties (currently 4 concrete
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* implementations) the two sets would be rather small
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public static boolean isAssociationProperty(Class<? extends CategoryProperty> clazz) {
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if (ASSOCIATION_PROPERTY_CLASSES.contains(clazz)) {
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if (NON_ASSOCIATION_PROPERTY_CLASSES.contains(clazz)) {
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if (AssociationProperty.class.isAssignableFrom(clazz)) {
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ASSOCIATION_PROPERTY_CLASSES.add(clazz);
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NON_ASSOCIATION_PROPERTY_CLASSES.add(clazz);
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public boolean generatesCategoryList() {
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public String getCategoryListTermText() {
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return CATEGORY_LIST_TERM_TEXT;
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public CategoryListTokenizer getCategoryListTokenizer(
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TokenStream tokenizer, EnhancementsIndexingParams indexingParams,
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TaxonomyWriter taxonomyWriter) {
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return new AssociationListTokenizer(tokenizer, indexingParams, this);
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public byte[] getCategoryTokenBytes(CategoryAttribute categoryAttribute) {
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AssociationProperty property = getAssociationProperty(categoryAttribute);
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if (property == null) {
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int association = property.getAssociation();
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int bytesNeeded = Vint8.bytesNeeded(association);
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byte[] buffer = new byte[bytesNeeded];
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Vint8.encode(association, buffer, 0);
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public static AssociationProperty getAssociationProperty(
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CategoryAttribute categoryAttribute) {
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AssociationProperty property = null;
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Set<Class<? extends CategoryProperty>> propertyClasses = categoryAttribute
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.getPropertyClasses();
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if (propertyClasses == null) {
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for (Class<? extends CategoryProperty> clazz : propertyClasses) {
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if (isAssociationProperty(clazz)) {
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property = (AssociationProperty) categoryAttribute
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public Object extractCategoryTokenData(byte[] buffer, int offset, int length) {
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Integer i = Integer.valueOf(Vint8.decode(buffer, new Position(offset)));
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public Class<? extends CategoryProperty> getRetainableProperty() {