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
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