Implementing a directory provider for hibernate search using MongoDB

Question

I would like to use this solution for my site on Heroku so I can index using the MongoDB does anyone know of a good tutorial or book that gives an in depth example of how to do this? Googling didn't really turn up anything for me.

Thanks.

Answer 1

I spent a long time on this because I was so new to Mongo DB and hadn't planned on using it until it seemed like a good solution for a search implementation on Heroku. I thought I would add this answer to help anyone else who wanted to do the same thing.

I used code from the lucene mongo db project located here:

https://github.com/mongoutils/mongo-lucene

Then created my own hibernate search directory provider class that interfaces with the lucene mongo db project. I used the org.hibernate.search.store.impl.RAMDirectoryProvider class as an outline to follow.

All thats left to do is to have your hibernate configuration point to your new class:

hibernate.search.default.directory_provider=com.foo.MongoLuceneDirectoryProvider

Here is my MongoLuceneDirectoryProvider class:

package com.foo.MongoLuceneDirectoryProvider

import java.io.IOException;
import java.net.UnknownHostException;
import java.util.Properties;
import java.util.concurrent.ConcurrentMap;

import org.apache.log4j.Logger;
import org.apache.lucene.store.Directory;
import org.hibernate.search.SearchException;
import org.hibernate.search.indexes.impl.DirectoryBasedIndexManager;
import org.hibernate.search.spi.BuildContext;
import org.hibernate.search.store.DirectoryProvider;
import org.hibernate.search.store.impl.DirectoryProviderHelper;

import com.github.mongoutils.collections.DBObjectSerializer;
import com.github.mongoutils.collections.MongoConcurrentMap;
import com.github.mongoutils.collections.SimpleFieldDBObjectSerializer;
import com.github.mongoutils.lucene.MapDirectory;
import com.github.mongoutils.lucene.MapDirectoryEntry;
import com.github.mongoutils.lucene.MapDirectoryEntrySerializer;
import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.Mongo;
import com.mongodb.MongoException;

public class MongoLuceneDirectoryProvider implements DirectoryProvider<Directory> {

    private Logger log = Logger.getLogger(MongoLuceneDirectoryProvider.class);

    private Directory directory;

    private String indexName;
    private Properties properties;

    @Override
    public void initialize(String directoryProviderName, Properties properties, BuildContext context) {

            indexName = directoryProviderName;
        this.properties = properties;

        Mongo mongo;

        try {
            mongo = new Mongo("localhost");

            DB db = mongo.getDB("testdb");
            DBCollection dbCollection = db.getCollection("testcollection");

            DBObjectSerializer<String> keySerializer = new SimpleFieldDBObjectSerializer<String>("key");
            DBObjectSerializer<MapDirectoryEntry> valueSerializer = new MapDirectoryEntrySerializer("value");
            ConcurrentMap<String, MapDirectoryEntry> store = new MongoConcurrentMap<String, MapDirectoryEntry>(dbCollection, keySerializer, valueSerializer);

            directory = new MapDirectory(store);
        }
        catch (UnknownHostException e) {
            log.error("While attempting to initalize Mongo directory provider", e);
        }
        catch (MongoException e) {
            log.error("While attempting to initalize Mongo directory provider", e);
        }
        catch (IOException e) {
            log.error("While attempting to initalize Mongo directory provider", e);
        }
    }

    @Override
    public void start(DirectoryBasedIndexManager indexManager) {

        try {
            directory.setLockFactory(DirectoryProviderHelper.createLockFactory(null, properties));
            properties = null;
            DirectoryProviderHelper.initializeIndexIfNeeded(directory);
        }
        catch (IOException e) {
            throw new SearchException("Unable to initialize index: " + indexName, e);
        }
    }

    @Override
    public void stop() {

        try {
            directory.close();
        }
        catch (IOException e) {
            log.error("While attempting to stop directory provider", e);
        }
    }

    @Override
    public Directory getDirectory() { return this.directory; }

}

Answer 2

If you want to help implementing it (I mean creating the Java code to support this configuration), please join the conversation in the more appropriate mailing list:

http://lists.jboss.org/pipermail/hibernate-dev/2013-January/009329.html

Subscribe here:

https://lists.jboss.org/mailman/listinfo/hibernate-dev

It should be straight-forward coding to integrate some existing components.