Java + MongoDB hello world example

Java mongodb hello world

A simple Java + MongoDB hello world example – how to connect, create database, collection and document, save, update, remove, get and display document (data).

Tools and technologies used :

  1. MongoDB 2.2.3
  2. MongoDB-Java-Driver 2.10.1
  3. JDK 1.6
  4. Maven 3.0.3
  5. Eclipse 4.2

P.S Maven and Eclipse are both optional, just my personal favorite development tool.

1. Create a Java Project

Create a simple Java project with Maven.

mvn archetype:generate -DgroupId=com.mkyong.core -DartifactId=mongodb 
  -DarchetypeArtifactId=maven-archetype-quickstart -DinteractiveMode=false

2. Get Mongo Java Driver

Download mongo-java driver from github. For Maven users, declares mongo-java driver in pom.xml.

pom.xml
<project ...>
  <dependencies>
 
	<dependency>
		<groupId>org.mongodb</groupId>
		<artifactId>mongo-java-driver</artifactId>
		<version>2.10.1</version>
	</dependency>
 
  </dependencies>
 
  <build>
	<plugins>
		<plugin>
			<groupId>org.apache.maven.plugins</groupId>
			<artifactId>maven-compiler-plugin</artifactId>
			<version>2.3.1</version>
			<configuration>
				<source>1.6</source>
				<target>1.6</target>
			</configuration>
		</plugin>
	        <plugin>
			<groupId>org.apache.maven.plugins</groupId>
			<artifactId>maven-eclipse-plugin</artifactId>
			<configuration>
				<downloadSources>true</downloadSources>
				<downloadJavadocs>true</downloadJavadocs>
			</configuration>
		</plugin>
 
	</plugins>
  </build>
 
</project>

3. Mongo Connection

Connect to MongoDB server. For MongoDB version >= 2.10.0, uses MongoClient.

	// Old version, uses Mongo
	Mongo mongo = new Mongo("localhost", 27017);
 
	// Since 2.10.0, uses MongoClient
	MongoClient mongo = new MongoClient( "localhost" , 27017 );

If MongoDB in secure mode, authentication is required.

	MongoClient mongoClient = new MongoClient();
	DB db = mongoClient.getDB("database name");
	boolean auth = db.authenticate("username", "password".toCharArray());

4. Mongo Database

Get database. If the database doesn’t exist, MongoDB will create it for you.

	DB db = mongo.getDB("database name");

Display all databases.

	List<String> dbs = mongo.getDatabaseNames();
	for(String db : dbs){
		System.out.println(db);
	}

5. Mongo Collection

Get collection / table.

	DB db = mongo.getDB("testdb");
	DBCollection table = db.getCollection("user");

Display all collections from selected database.

	DB db = mongo.getDB("testdb");
	Set<String> tables = db.getCollectionNames();
 
	for(String coll : tables){
		System.out.println(coll);
	}
Note
In RDBMS, collection is equal to table.

6. Save example

Save a document (data) into a collection (table) named “user”.

	DBCollection table = db.getCollection("user");
	BasicDBObject document = new BasicDBObject();
	document.put("name", "mkyong");
	document.put("age", 30);
	document.put("createdDate", new Date());
	table.insert(document);

Refer to this Java MongoDB insert example.

7. Update example

Update a document where “name=mkyong”.

	DBCollection table = db.getCollection("user");
 
	BasicDBObject query = new BasicDBObject();
	query.put("name", "mkyong");
 
	BasicDBObject newDocument = new BasicDBObject();
	newDocument.put("name", "mkyong-updated");
 
	BasicDBObject updateObj = new BasicDBObject();
	updateObj.put("$set", newDocument);
 
	table.update(query, updateObj);

Refer to this Java MongoDB update example.

8. Find example

Find document where “name=mkyong”, and display it with DBCursor

	DBCollection table = db.getCollection("user");
 
	BasicDBObject searchQuery = new BasicDBObject();
	searchQuery.put("name", "mkyong");
 
	DBCursor cursor = table.find(searchQuery);
 
	while (cursor.hasNext()) {
		System.out.println(cursor.next());
	}

Refer to this Java MongoDB search query example.

9. Delete example

Find document where “name=mkyong”, and delete it.

	DBCollection table = db.getCollection("user");
 
	BasicDBObject searchQuery = new BasicDBObject();
	searchQuery.put("name", "mkyong");
 
	table.remove(searchQuery);

Refer to this Java MongoDB delete example.

10. Hello World

Let review a complete Java + MongoDB example, see comments for self-explanatory.

App.java
package com.mkyong.core;
 
import java.net.UnknownHostException;
import java.util.Date;
import com.mongodb.BasicDBObject;
import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.DBCursor;
import com.mongodb.MongoClient;
import com.mongodb.MongoException;
 
/**
 * Java + MongoDB Hello world Example
 * 
 */
public class App {
  public static void main(String[] args) {
 
    try {
 
	/**** Connect to MongoDB ****/
	// Since 2.10.0, uses MongoClient
	MongoClient mongo = new MongoClient("localhost", 27017);
 
	/**** Get database ****/
	// if database doesn't exists, MongoDB will create it for you
	DB db = mongo.getDB("testdb");
 
	/**** Get collection / table from 'testdb' ****/
	// if collection doesn't exists, MongoDB will create it for you
	DBCollection table = db.getCollection("user");
 
	/**** Insert ****/
	// create a document to store key and value
	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());
	}
 
	/**** Update ****/
	// search document where name="mkyong" and update it with new values
	BasicDBObject query = new BasicDBObject();
	query.put("name", "mkyong");
 
	BasicDBObject newDocument = new BasicDBObject();
	newDocument.put("name", "mkyong-updated");
 
	BasicDBObject updateObj = new BasicDBObject();
	updateObj.put("$set", newDocument);
 
	table.update(query, updateObj);
 
	/**** Find and display ****/
	BasicDBObject searchQuery2 
	    = new BasicDBObject().append("name", "mkyong-updated");
 
	DBCursor cursor2 = table.find(searchQuery2);
 
	while (cursor2.hasNext()) {
		System.out.println(cursor2.next());
	}
 
	/**** Done ****/
	System.out.println("Done");
 
    } catch (UnknownHostException e) {
	e.printStackTrace();
    } catch (MongoException e) {
	e.printStackTrace();
    }
 
  }
}

Output…

{ "_id" : { "$oid" : "51398e6e30044a944cc23e2e"} , "name" : "mkyong" , "age" : 30 , "createdDate" : { "$date" : "2013-03-08T07:08:30.168Z"}}
{ "_id" : { "$oid" : "51398e6e30044a944cc23e2e"} , "age" : 30 , "createdDate" : { "$date" : "2013-03-08T07:08:30.168Z"} , "name" : "mkyong-updated"}
Done

Let use mongo console to check the created database “testdb”, collection “user”, and document.

$ mongo
MongoDB shell version: 2.2.3
connecting to: test
 
> show dbs
testdb	0.203125GB
 
> use testdb
switched to db testdb
 
> show collections
system.indexes
user
> db.user.find()
{ "_id" : ObjectId("51398e6e30044a944cc23e2e"), "age" : 30, "createdDate" : ISODate("2013-03-08T07:08:30.168Z"), "name" : "mkyong-updated" }

Download Source Code

Download it – Java-mongodb-hello-world-example.zip (13KB)

References

  1. Getting started with Java driver
  2. Java-MongoDB driver
Tags :

About the Author

mkyong
Founder of Mkyong.com and HostingCompass.com, love Java and open source stuff. Follow him on Twitter, or befriend him on Facebook or Google Plus. If you like my tutorials, consider make a donation to these charities.

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  • paul

    dont you want to close the connections?

  • kranthi

    Hi mkyong,

    Thanks for your sharing your knowledge with us.They are really helpful for us

  • Mediha

    Instead of creating a maven project are there any jars that we can import and then import them?

    • Mediha

      Instead of creating a maven project are there any jars that we can import and then use those instead of pom.xml dependencies?

      • a

        Why would you ever want to do that? Maven has made everything so easy.

  • nirmal
  • ajit

    For a beginner like me , your tutorials are too good. I appreciate the work that you do to make people understand all the concepts.
    Thanks a lot.

  • dreamshutter

    Do not need mongoClient.close() in example source?
    use only upper code then mongo has too many client connection
    then it works slower

  • http://[email protected] Ramath

    Nice one . Good as a starter ! . Appreciate your effort .

  • Neethu

    I have worked on Spring data integration with mango db in java application, can this be done in struts application aslo, I tried to find some examples online but could not find any.

    • http://www.mkyong.com mkyong

      Absolutely yes, Spring is build for integration, Google Spring + Struts integration example.

  • netaji

    Excellent and very useful for beginers.

  • Macluq

    It fails:

    03-May-2011 11:32:58 com.mongodb.DBTCPConnector fetchMaxBsonObjectSize
    WARNING: null
    java.io.IOException: couldn’t connect to [HOSTNAME/HOSTIP:27017] bc:java.net.ConnectException: Connection refused: connect
    at com.mongodb.DBPort._open(DBPort.java:205)
    (…)

    • http://www.mkyong.com mkyong

      obviously, cant connect to your mongodb.

      Make sure your mongodb is started and you are able to connect with the build-in mongo client.

      • Macluq

        thanks, i’ll try that.

        • Alex Beggs

          I ran into a similar issue using the Java driver connecting to a server (mongod.exe). Make sure you use the -rest flag. That seemed to work for me.