lucene 4.0

package com.fox.facet;

import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

import org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.analysis.standard.StandardAnalyzer;
import org.apache.lucene.document.Document;
import org.apache.lucene.document.Field.Store;
import org.apache.lucene.document.StringField;
import org.apache.lucene.facet.index.CategoryDocumentBuilder;
import org.apache.lucene.facet.search.FacetsCollector;
import org.apache.lucene.facet.search.params.CountFacetRequest;
import org.apache.lucene.facet.search.params.FacetSearchParams;
import org.apache.lucene.facet.search.results.FacetResult;
import org.apache.lucene.facet.search.results.FacetResultNode;
import org.apache.lucene.facet.taxonomy.CategoryPath;
import org.apache.lucene.facet.taxonomy.TaxonomyReader;
import org.apache.lucene.facet.taxonomy.TaxonomyWriter;
import org.apache.lucene.facet.taxonomy.directory.DirectoryTaxonomyReader;
import org.apache.lucene.facet.taxonomy.directory.DirectoryTaxonomyWriter;
import org.apache.lucene.index.DirectoryReader;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.index.IndexWriter;
import org.apache.lucene.index.IndexWriterConfig;
import org.apache.lucene.index.IndexWriterConfig.OpenMode;
import org.apache.lucene.index.Term;
import org.apache.lucene.search.IndexSearcher;
import org.apache.lucene.search.MultiCollector;
import org.apache.lucene.search.Query;
import org.apache.lucene.search.TermQuery;
import org.apache.lucene.search.TopScoreDocCollector;
import org.apache.lucene.store.Directory;
import org.apache.lucene.store.FSDirectory;
import org.apache.lucene.util.Version;

public class FacetingExample {
    private static final String INDEX = "d:/facet/index";
    private static final String INDEX_TAXO = "d:/facet/taxo";

    public static void main(final String[] args) throws IOException {
        Directory dir = FSDirectory.open(new File(INDEX));
        Directory taxoDir = FSDirectory.open(new File(INDEX_TAXO));
        Analyzer analyzer = new StandardAnalyzer(Version.LUCENE_40);
        IndexWriterConfig iwc = new IndexWriterConfig(Version.LUCENE_40, analyzer);
        iwc.setOpenMode(OpenMode.CREATE);
        IndexWriter writer = new IndexWriter(dir, iwc);
        TaxonomyWriter taxoWriter = new DirectoryTaxonomyWriter(taxoDir, OpenMode.CREATE_OR_APPEND);

        List<Book> books = Arrays.asList(new Book("Tom Sawyer", "Mark Twain", "1840", "Novel"), new Book("Collected Tales",
                "Mark Twain", "1850", "Novel"), new Book("The Trial", "Franz Kafka", "1901", "Novel"), new Book("Some book",
                "Some author", "1901", "Novel"));

        createDocuments(writer, taxoWriter, books);
        taxoWriter.commit();
        writer.commit();
        writer.close();
        taxoWriter.close();

        IndexReader indexReader = DirectoryReader.open(dir);
        IndexSearcher searcher = new IndexSearcher(indexReader);
        TaxonomyReader taxoReader = new DirectoryTaxonomyReader(taxoDir);
        Query q = new TermQuery(new Term("category", "Novel"));
        TopScoreDocCollector tdc = TopScoreDocCollector.create(10, true);
        FacetSearchParams facetSearchParams = new FacetSearchParams();
        facetSearchParams.addFacetRequest(new CountFacetRequest(new CategoryPath("author"), 10));
        facetSearchParams.addFacetRequest(new CountFacetRequest(new CategoryPath("category"), 10));
        facetSearchParams.addFacetRequest(new CountFacetRequest(new CategoryPath("published"), 10));
        FacetsCollector facetsCollector = new FacetsCollector(facetSearchParams, indexReader, taxoReader);
        searcher.search(q, MultiCollector.wrap(tdc, facetsCollector));
        List<FacetResult> res = facetsCollector.getFacetResults();
        System.out.println("Search for books with the category:Novel returned : " + res.size()
                + " results
---------------------------------");
        for (final FacetResult r : res) {
            System.out.println("
Matching " + r.getFacetResultNode().getLabel() + ":
------------------------------------");
            for (FacetResultNode n : r.getFacetResultNode().getSubResults()) {
                System.out.println(String.format("	%s: %.0f", n.getLabel().lastComponent(), n.getValue()));
            }
        }
    }

    private static void createDocuments(final IndexWriter writer, final TaxonomyWriter taxoWriter, final List<Book> books)
            throws IOException {
        for (final Book b : books) {
            Document doc = new Document();
            doc.add(new StringField("title", b.getTitle(), Store.YES));
            doc.add(new StringField("category", b.getCategory(), Store.YES));
            List<CategoryPath> categories = new ArrayList<CategoryPath>();
            categories.add(new CategoryPath("author", b.getAuthor()));
            categories.add(new CategoryPath("category", b.getCategory()));
            categories.add(new CategoryPath("published", b.getPublished()));
            CategoryDocumentBuilder categoryDocBuilder = new CategoryDocumentBuilder(taxoWriter);
            categoryDocBuilder.setCategoryPaths(categories);
            categoryDocBuilder.build(doc);
            writer.addDocument(doc);
        }
    }
}

class Book {
    private final String title;
    private final String author;
    private final String published;
    private final String category;

    public Book(final String title, final String author, final String published, final String category) {
        this.title = title;
        this.author = author;
        this.published = published;
        this.category = category;
    }

    public String getTitle() {
        return title;
    }

    public String getAuthor() {
        return author;
    }

    public String getPublished() {
        return published;
    }

    public String getCategory() {
        return category;
    }
}

Result

Search for books with the category:Novel returned : 3 results
---------------------------------

Matching author:
------------------------------------
    Mark Twain: 2
    Some author: 1
    Franz Kafka: 1

Matching category:
------------------------------------
    Novel: 4

Matching published:
------------------------------------
    1901: 2
    1850: 1
    1840: 1