<p>In this tutorial we will discuss an example of java which describe how to get the collection from MongoDb and other functions of collection.</p>
<p>To get a collection to use, just specify the name of the collection to the getCollection(String collectionName) method:</p>
<pre class="highlight" name="code">DBCollection coll = db.getCollection("dineshonjavaCollection");
</pre>
<p>Once you have this collection object, you can now do things like insert data, query for data, etc. Suppose &#8220;dineshonjavaCollection&#8221; if this collection already created not created on the mongoDB then return the &#8220;dineshonjavaCollection&#8221; else it create new &#8220;dineshonjavaCollection&#8221; in the MongoDB.</p>
<p>com.mongodb.DBCollection is abstract class. This class provides a skeleton implementation of a database collection.<br />
A typical invocation sequence is thus </p>
<pre class="highlight" name="code">Mongo mongo = new Mongo( new DBAddress( "localhost", 127017 ) );
 DB db = mongo.getDB( "dineshonjavaDB" );
 DBCollection collection = db.getCollection( "dineshonjavaCollection" );
</pre>
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<p>If you do not know the collection name, use db.getCollectionNames() to get the entire list of collection names from a selected database.</p>
<pre class="highlight" name="code">DB db = mongo.getDB("dineshonjavaDB");
Set<;String>; collections = db.getCollectionNames();
 
for (String collectionName : collections) {
 System.out.println(collectionName);
}
</pre>
<p>If &#8220;dineshonjavaDB&#8221; contains collection name &#8220;dineshonjavaCollection&#8221;, then you will see following result :</p>
<p>system.indexes //system collection<br />
system.users //system collection<br />
dineshonjavaCollection</p>
<p>Full example to get collection from MongoDB, via Java driver.</p>
<pre class="highlight" name="code">package com.dineshonjava.mongo.test;

import java.net.UnknownHostException;
import java.util.Set;

import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.Mongo;
import com.mongodb.MongoException;

/**
 * @author Dinesh Rajput
 *
 */
public class CollectiomDemo {

 /**
 * @param args
 */
 public static void main(String[] args) {
 try {
 // connect to mongoDB, IP and port number
 Mongo mongo = new Mongo("localhost", 27017);
 
 // get database from MongoDB,
 // if database doesn't exists, mongoDB will create it automatically
 DB db = mongo.getDB("dineshonjavaDB");
 
 // get list of collections
 Set<;String>;collections = db.getCollectionNames();
 
 for (String collectionName : collections) {
 System.out.println(collectionName);
 }
 System.out.println("************************************************"); 
 // Get collection from MongoDB, database named "dineshonjavaDB"
 // if collection doesn't exists, mongoDB will create it automatically
 DBCollection collection = db.getCollection("dineshonjavaCollection");
 
 System.out.println(collection);
 
 System.out.println("Done");
 
 } catch (UnknownHostException e) {
 e.printStackTrace();
 } catch (MongoException e) {
 e.printStackTrace();
 }
 
 }

}
</pre>
<p>
If every thing is fine then run as a java application then we will get following output on console.</p>
<div style="background-color: #ff99cc;"><b>output:</b><br />
dineshonjavaCollection<br />
employees<br />
system.indexes<br />
************************************************<br />
dineshonjavaCollection<br />
Done</div>
<p>
<b>Reference</b><br />
<a href="http://www.mongodb.org/display/DOCS/Java+Tutorial#JavaTutorial-GettingACollection" target="_blank">Java tutorial – MongoDB</a></p>
<p><b>Download Source Code + Libs</b><br />
<b><a href="https://sites.google.com/site/dinesh9582486434/my-forms/MongoDBCollectionDemo.zip?attredirects=0&;d=1" target="_blank">MongoDBCollectionDemo.zip</a> </b></p>
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