com.mathworks.xzheng.advsearching.BooksLikeThis.java Source code

Introduction

Here is the source code for com.mathworks.xzheng.advsearching.BooksLikeThis.java

Source

package com.mathworks.xzheng.advsearching;

/**
 * Copyright Manning Publications Co.
 *
 * Licensed 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 lan      
 */

import java.io.IOException;

import org.apache.lucene.document.Document;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.index.Term;
import org.apache.lucene.index.Terms;
import org.apache.lucene.index.TermsEnum;
import org.apache.lucene.search.BooleanClause;
import org.apache.lucene.search.BooleanQuery;
import org.apache.lucene.search.IndexSearcher;
import org.apache.lucene.search.TermQuery;
import org.apache.lucene.search.TopDocs;
import org.apache.lucene.store.Directory;

import com.mathworks.xzheng.common.TestUtil;
import org.apache.lucene.util.BytesRef;

// From chapter 5
public class BooksLikeThis {

    public static void main(String[] args) throws IOException {
        Directory dir = TestUtil.getBookIndexDirectory();

        IndexReader reader = IndexReader.open(dir);
        int numDocs = reader.maxDoc();

        BooksLikeThis blt = new BooksLikeThis(reader);
        for (int i = 0; i < numDocs; i++) { // #1
            System.out.println();
            Document doc = reader.document(i);
            System.out.println(doc.get("title"));

            Document[] docs = blt.docsLike(i, 10); // #2
            if (docs.length == 0) {
                System.out.println("  None like this");
            }
            for (Document likeThisDoc : docs) {
                System.out.println("  -> " + likeThisDoc.get("title"));
            }
        }
        reader.close();
        dir.close();
    }

    private IndexReader reader;
    private IndexSearcher searcher;

    public BooksLikeThis(IndexReader reader) {
        this.reader = reader;
        searcher = new IndexSearcher(reader);
    }

    public Document[] docsLike(int id, int max) throws IOException {
        Document doc = reader.document(id);

        String[] authors = doc.getValues("author");
        BooleanQuery authorQuery = new BooleanQuery(); // #3
        for (String author : authors) { // #3
            authorQuery.add(new TermQuery(new Term("author", author)), // #3
                    BooleanClause.Occur.SHOULD); // #3
        }
        authorQuery.setBoost(2.0f);

        Terms terms = reader.getTermVector(id, "subject"); // #4

        BooleanQuery subjectQuery = new BooleanQuery(); // #4
        TermsEnum termsEnum = terms.iterator(null);
        BytesRef text;
        while ((text = termsEnum.next()) != null) { // #4
            TermQuery tq = new TermQuery( // #4
                    new Term("subject", text.utf8ToString())); // #4
            subjectQuery.add(tq, BooleanClause.Occur.SHOULD); // #4
        }

        BooleanQuery likeThisQuery = new BooleanQuery(); // #5
        likeThisQuery.add(authorQuery, BooleanClause.Occur.SHOULD); // #5
        likeThisQuery.add(subjectQuery, BooleanClause.Occur.SHOULD); // #5

        likeThisQuery.add(new TermQuery( // #6
                new Term("isbn", doc.get("isbn"))), BooleanClause.Occur.MUST_NOT); // #6

        // System.out.println("  Query: " +
        //    likeThisQuery.toString("contents"));
        TopDocs hits = searcher.search(likeThisQuery, 10);
        int size = max;
        if (max > hits.scoreDocs.length)
            size = hits.scoreDocs.length;

        Document[] docs = new Document[size];
        for (int i = 0; i < size; i++) {
            docs[i] = reader.document(hits.scoreDocs[i].doc);
        }

        return docs;
    }
}
/*
#1 Iterate over every book
#2 Look up books like this
#3 Boosts books by same author
#4 Use terms from "subject" term vectors 
#5 Create final query
#6 Exclude current book
*/