Lucene-6.4.2 : No class found DefaultSimilarity, tried adding queries.

Question

I am working on testing Apache lucene for text based search in our project. Unfortunately, I am having problem with missing libraries. I tried adding the lucene-queries, but that didn't help. What am I doing wrong?

ErrorLog :

Caused by: java.lang.NoClassDefFoundError: org/apache/lucene/search/similarities/DefaultSimilarity
    at org.hibernate.search.spi.SearchIntegratorBuilder.createCleanFactoryState(SearchIntegratorBuilder.java:287)
    at org.hibernate.search.spi.SearchIntegratorBuilder.buildNewSearchFactory(SearchIntegratorBuilder.java:186)
    at org.hibernate.search.spi.SearchIntegratorBuilder.buildSearchIntegrator(SearchIntegratorBuilder.java:117)
    at org.hibernate.search.hcore.impl.HibernateSearchSessionFactoryObserver.sessionFactoryCreated(HibernateSearchSessionFactoryObserver.java:66)
    at org.hibernate.internal.SessionFactoryObserverChain.sessionFactoryCreated(SessionFactoryObserverChain.java:52)
    at org.hibernate.internal.SessionFactoryImpl.<init>(SessionFactoryImpl.java:588)
    at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1859)
    at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1930)
    at org.springframework.orm.hibernate4.LocalSessionFactoryBuilder.buildSessionFactory(LocalSessionFactoryBuilder.java:372)
    at org.springframework.orm.hibernate4.LocalSessionFactoryBean.buildSessionFactory(LocalSessionFactoryBean.java:454)
    at org.springframework.orm.hibernate4.LocalSessionFactoryBean.afterPropertiesSet(LocalSessionFactoryBean.java:439)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1633)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1570)
    ... 98 more
Caused by: java.lang.ClassNotFoundException: org.apache.lucene.search.similarities.DefaultSimilarity
    at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1858)
    at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1701)
    ... 111 more

POM.xml :

  <!-- https://mvnrepository.com/artifact/org.apache.lucene/lucene-core -->
        <dependency>
            <groupId>org.apache.lucene</groupId>
            <artifactId>lucene-core</artifactId>
            <version>6.4.2</version>
        </dependency>

Code I am trying :

  @Override
    public void saveIndexes() {
        //Apache Lucene Indexing Directory .txt files
        try {
            //indexing directory
            Path path = Paths.get("/home/akshay/index/");
            Directory directory = org.apache.lucene.store.FSDirectory.open(path);
            IndexWriterConfig config = new IndexWriterConfig(new SimpleAnalyzer());
            IndexWriter indexWriter = new IndexWriter(directory, config);
            indexWriter.deleteAll();
            File f = new File("/home/akshay/textfiles/"); // current directory
            for (File file : f.listFiles()) {
                System.out.println("indexed " + file.getCanonicalPath());
                org.apache.lucene.document.Document doc = new org.apache.lucene.document.Document();
                doc.add(new TextField("path", file.getName(), Field.Store.YES));
                FileInputStream is = new FileInputStream(file);
                BufferedReader reader = new BufferedReader(new InputStreamReader(is));
                StringBuffer stringBuffer = new StringBuffer();
                String line;
                while((line = reader.readLine())!=null){
                    stringBuffer.append(line).append("\n");
                }
                reader.close();
                doc.add(new TextField("contents", stringBuffer.toString(), Field.Store.YES));
                indexWriter.addDocument(doc);
            }
            indexWriter.close();
            directory.close();
        } catch (Exception e) {
            // TODO: handle exception
            e.printStackTrace();
        }
    }

    @Override
    public void searchLucene(String text) {
        //Apache Lucene searching text inside .txt files
        try {
            Path path = Paths.get("/home/akshay/index/");
            Directory directory = FSDirectory.open(path);
            IndexReader indexReader =  DirectoryReader.open(directory);
            IndexSearcher indexSearcher = new IndexSearcher(indexReader);
            QueryParser queryParser = new QueryParser("contents",  new StandardAnalyzer());
            Query query = queryParser.parse(text);
            TopDocs topDocs = indexSearcher.search(query,10);
            System.out.println("totalHits " + topDocs.totalHits);
            for (ScoreDoc scoreDoc : topDocs.scoreDocs) {
                org.apache.lucene.document.Document document = indexSearcher.doc(scoreDoc.doc);
                System.out.println("path " + document.get("path"));
                System.out.println("content " + document.get("contents"));
            }
        } catch (Exception e) {
            // TODO: handle exception
            e.printStackTrace();
        }
    }

Any ideas, thank you. :-)

Answer 1

Actually the class was deprecated already in 5.4.1 , when looking for it in the 6.4.2 version it does not exist anymore, see the message:

Use ClassicSimilarity for equivilent behavior, or consider switching to BM25Similarity which will become the new default in Lucene 6.0

See also :

• LUCENE-6789: IndexSearcher's default Similarity is changed to BM25Similarity. Use ClassicSimilarity to get the old vector space DefaultSimilarity. (Robert Muir)

Either downgrade your lucene core dependency to 5.5.4, or use in your code either ClassicSimilarity or BM25Similarity