MongoDBHelper

package util;

import com.mongodb.MongoClient;
import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.BasicDBObject;
import com.mongodb.DBObject;
import com.mongodb.DBCursor;
import java.net.UnknownHostException;
import java.util.List;
import java.util.Set;

public class MongoDBHelper {

    private static MongoDBHelper uniqueInstance = null;

    private MongoClient mongoClient;
    private DB db;
    private DBCollection coll;

    private  MongoDBHelper(String serverAddress, int port, String dbName, String collectionName ){
        try{
            mongoClient = new MongoClient(serverAddress, port);
            db = mongoClient.getDB(dbName);
            coll = db.getCollection(collectionName);
        } catch (UnknownHostException e) {
            e.printStackTrace();
        }
    }

    public static MongoDBHelper getHelper(){
        if(null==uniqueInstance){
            uniqueInstance =  new MongoDBHelper("localhost",27017,"test","test");
        }
        return uniqueInstance;
    }

    public void switchDB(String dbName){
        db = mongoClient.getDB(dbName);
    }

    public void switchCollection(String collectionName){
        coll = db.getCollection(collectionName);
    }

    public void switchDBCollection(String dbName, String collectionName){
        switchDB(dbName);
        switchCollection(collectionName);
    }

    public void printInfo(){
        print("All DBs:");
        for (String s : mongoClient.getDatabaseNames()) {
               print(s+" ");
        }
        print("\n\ncurrent DB:");
        print("\n\nall collections");
        for (String s : db.getCollectionNames()) {
            print(s+" ");
        }
        print("\n\ncurrent collections");
        print("\n\nitems in colletion: ");
        print(String.valueOf(coll.getCount()));
    }

    static void print(String out){
        System.out.print(out);
    }


}