org.wikidata.couchbase.MongoPersistHandler.java Source code

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Here is the source code for org.wikidata.couchbase.MongoPersistHandler.java

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/*******************************************************************************
 * Copyright (c) 2014 Daniel Murygin.
 *
 * This program is free software: you can redistribute it and/or 
 * modify it under the terms of the GNU Lesser General Public License 
 * as published by the Free Software Foundation, either version 3 
 * of the License, or (at your option) any later version.
 * This program is distributed in the hope that it will be useful,    
 * but WITHOUT ANY WARRANTY; without even the implied warranty 
 * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  
 * See the GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program. 
 * If not, see <http://www.gnu.org/licenses/>.
 * 
 * Contributors:
 *     Daniel Murygin <dm[at]sernet[dot]de> - initial API and implementation
 ******************************************************************************/
package org.wikidata.couchbase;

import java.io.IOException;
import java.net.UnknownHostException;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;

import org.apache.log4j.Logger;

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.mongodb.BasicDBObject;
import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.DBCursor;
import com.mongodb.DBObject;
import com.mongodb.MongoClient;
import com.mongodb.MongoException;
import com.mongodb.ServerAddress;
import com.mongodb.util.JSON;

/**
 *
 *
 * @author Daniel Murygin <dm[at]sernet[dot]de>
 */
public class MongoPersistHandler implements IPersistHandler {

    private static final Logger LOG = Logger.getLogger(MongoPersistHandler.class);

    public static final String ITEM_COLLECTION_NAME = "item";
    public static final String CLAIM_COLLECTION_NAME = "claim";

    private Configuration conf;

    private MongoClient mongoClient = null;
    private DB db = null;
    private DBCollection collection = null;

    public MongoPersistHandler(Configuration conf) {
        super();
        this.conf = conf;
        try {
            createMongoClient();
        } catch (UnknownHostException e) {
            LOG.error("Unknown host. Can not create MongoDB client.", e);
        }
    }

    private void createMongoClient() throws UnknownHostException {
        // init CouchbaseClient
        List<ServerAddress> adressList = new LinkedList<ServerAddress>();
        for (String url : conf.getDbUrls()) {
            adressList.add(new ServerAddress(url));
        }
        mongoClient = new MongoClient(adressList);
    }

    /* (non-Javadoc)
     * @see org.wikidata.couchbase.IPersistHandler#save(java.lang.Integer, java.lang.String)
     */
    @Override
    public void save(Integer id, String jsonString) {
        DBObject dbObject = null;
        try {
            dbObject = new BasicDBObject();
            JsonNode node = createJsonNode(jsonString);
            JsonNode transformedNode = transformNode(node);
            String jsonText = transformedNode.toString();
            dbObject.put("item", JSON.parse(jsonText));
            String idString = buildDocumentKey(id);
            dbObject.put("_id", idString);
            getCollection().insert(dbObject);
        } catch (MongoException.DuplicateKey e) {
            LOG.info("Item " + id + " exists and is updated");
            if (LOG.isDebugEnabled()) {
                LOG.debug("Stacktrace: ", e);
            }
            getCollection().save(dbObject);
        } catch (Exception e) {
            LOG.error("Error while saving Object.", e);
            throw new RuntimeException("Error while saving Object.", e);
        }
    }

    @Override
    public void save(DBObject dbObject) {
        try {
            getCollection().insert(dbObject);
        } catch (MongoException.DuplicateKey e) {
            LOG.info("Item " + dbObject.get("_id") + " exists and is updated");
            if (LOG.isDebugEnabled()) {
                LOG.debug("Stacktrace: ", e);
            }
            getCollection().save(dbObject);
        } catch (Exception e) {
            LOG.error("Error while saving Object.", e);
            throw new RuntimeException("Error while saving Object.", e);
        }
    }

    @Override
    public List<DBObject> load(int start, int limit) {
        DBCursor cursor = getCollection().find();
        cursor.skip(start);
        cursor.limit(limit);
        List<DBObject> result = new LinkedList<DBObject>();
        try {
            while (cursor.hasNext()) {
                result.add(cursor.next());
            }
        } finally {
            cursor.close();
        }
        return result;
    }

    /* (non-Javadoc)
     * @see org.wikidata.couchbase.IPersistHandler#count()
     */
    @Override
    public long count() {
        return getCollection().getCount();
    }

    private JsonNode transformNode(JsonNode node) {
        Map.Entry<String, JsonNode> entry = node.iterator().next().fields().next();
        JsonNode transformedNode = entry.getValue();
        return transformedNode;
    }

    private JsonNode createJsonNode(String jsonString) throws IOException, JsonProcessingException {
        ObjectMapper mapper = new ObjectMapper();
        return mapper.readTree(jsonString);
    }

    public static String buildDocumentKey(Integer startId) {
        StringBuilder sb = new StringBuilder();
        sb.append("wikidata:item:");
        sb.append(startId);
        return sb.toString();
    }

    /* (non-Javadoc)
     * @see org.wikidata.couchbase.IPersistHandler#shutdown()
     */
    @Override
    public void shutdown() {
        mongoClient.close();
    }

    private DB getDb() {
        if (db == null) {
            db = mongoClient.getDB(conf.getDb());
        }
        return db;
    }

    private DBCollection getCollection() {
        if (collection == null) {
            collection = getDb().getCollection(MongoPersistHandler.ITEM_COLLECTION_NAME);
        }
        return collection;
    }

    /* (non-Javadoc)
     * @see org.wikidata.couchbase.IPersistHandler#find(com.mongodb.BasicDBObject)
     */
    @Override
    public DBCursor find(BasicDBObject doc) {
        return getCollection().find(doc);
    }

}