After the firts posts on Kotlin, i want to creating something more difficult. And i chose to try a database connection in Kotlin.
In this exercise i chose to connect my little application to a Mongo database. This choice is driven by a book that i started to read in these days: “MongoDb in action”, because i want to know more about this type of database. So i decided to try to use both new things: kotlin and MongoDB.
This exercise is organized in this way: first part is a java test connection and operations with MongoDB then the same operations are written in Kotlin.
Ok, let’s start with code:
Firt of all create the instance of mongodb client and create te DB:
import com.mongodb.*; import java.net.UnknownHostException; import java.util.Date; /** * Created by Claudio on 30/04/16. */ public class Main { public static void main(String[] args) { try { MongoClient mongo = new MongoClient( "localhost" , 27017 ); DB db = mongo.getDB("testDB"); DBCollection table; table = db.getCollection ("clienti"); //Insert document BasicDBObject document = new BasicDBObject(); document.put("name", "mkyong"); document.put("age", 30); document.put ("createdDate", new Date ( )); table.insert(document); /**** Find and display ****/ BasicDBObject searchQuery = new BasicDBObject(); searchQuery.put("name", "mkyong"); DBCursor cursor = table.find(searchQuery); while (cursor.hasNext()) { System.out.println(cursor.next()); } } catch (UnknownHostException e) { e.printStackTrace ( ); } catch (MongoException e) { e.printStackTrace(); } } }
this is a little example to show how to:
- connect to MongoDB (line 14)
- create or get database (lines 16-19)
- create a document (lines 22-26)
- get insered data (lines 29-32)
- show on standart output the datas (34-35)
The result of running this code is:
The next part is focused on the Kotlin equivalent code.
I am computer system engineer to be..
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