Tag: CRUD operators

MongoDB with Java

Installation

Before we start using MongoDB in our Java programs, we need to make sure that we have MongoDB JDBC Driver and Java set up on the machine. You can check Java tutorial for Java installation on your machine. Now, let us check how to set up MongoDB JDBC driver.

  • You need to download the jar from the path Download mongo.jar. Make sure to download latest release of it.
  • You need to include the mongo.jar into your classpath.

Connect to database

To connect database, you need to specify database name, if database doesn’t exist then mongodb creates it automatically.

Code snippets to connect to database would be as follows:

import com.mongodb.MongoClient;import com.mongodb.MongoException;import com.mongodb.WriteConcern;import com.mongodb.DB;import com.mongodb.DBCollection;import com.mongodb.BasicDBObject;import com.mongodb.DBObject;import com.mongodb.DBCursor;import com.mongodb.ServerAddress;import java.util.Arrays;publicclassMongoDBJDBC{publicstaticvoid main(String args[]){try{// To connect to mongodb serverMongoClient mongoClient =newMongoClient("localhost",27017);// Now connect to your databases
         DB db = mongoClient.getDB("test");System.out.println("Connect to database successfully");boolean auth = db.authenticate(myUserName, myPassword);System.out.println("Authentication: "+auth);}catch(Exception e){System.err.println( e.getClass().getName()+": "+ e.getMessage());}}}

Now, let’s compile and run above program to create our database test. You can change your path as per your requirement. We are assuming current version of JDBC driver mongo-2.10.1.jar is available in the current path

$javac MongoDBJDBC.java
$java -classpath ".:mongo-2.10.1.jar"MongoDBJDBCConnect to database successfully
Authentication:true

If you are going to use Windows machine, then you can compile and run your code as follows:

$javac MongoDBJDBC.java
$java -classpath ".;mongo-2.10.1.jar"MongoDBJDBCConnect to database successfully
Authentication:true

Value of auth will be true, if the user name and password are valid for the selected database.

Create a collection

To create a collection, createCollection() method of com.mongodb.DB class is used.

Code snippets to create a collection:

import com.mongodb.MongoClient;
import com.mongodb.MongoException;
import com.mongodb.WriteConcern;
import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.BasicDBObject;
import com.mongodb.DBObject;
import com.mongodb.DBCursor;
import com.mongodb.ServerAddress;
import java.util.Arrays;
public class MongoDBJDBC{
public static void main(String args[]){
try{// To connect to mongodb server
MongoClient mongoClient =new MongoClient("localhost",27017);// Now connect to your databases
DB db = mongoClient.getDB("test");System.out.println("Connect to database successfully");
boolean auth = db.authenticate(myUserName, myPassword);
System.out.println("Authentication: "+auth);
DBCollection coll = db.createCollection("mycol");
System.out.println("Collection created successfully");
}
catch(Exception e)
{
System.err.println( e.getClass().getName()+": "+ e.getMessage());
}}}

When program is compiled and executed, it will produce the following result:

Connect to database successfully
Authentication:trueCollection created successfully

Getting/ selecting a collection

To get/select a collection from the database, getCollection() method of com.mongodb.DBCollection class is used.

Code snippets to get/select a collection:

import com.mongodb.MongoClient;
import com.mongodb.MongoException;
import com.mongodb.WriteConcern;
import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.BasicDBObject;
import com.mongodb.DBObject;
import com.mongodb.DBCursor;
import com.mongodb.ServerAddress;
import java.util.Arrays;
publicclassMongoDBJDBC{public static void main(String args[]){
try{// To connect to mongodb server
MongoClient mongoClient =newMongoClient("localhost",27017);// Now connect to your databases
DB db = mongoClient.getDB("test");
System.out.println("Connect to database successfully");
boolean auth = db.authenticate(myUserName, myPassword);
System.out.println("Authentication: "+auth);
DBCollection coll = db.createCollection("mycol");
System.out.println("Collection created successfully");
DBCollection coll = db.getCollection("mycol");
System.out.println("Collection mycol selected successfully");
}catch(Exception e){
System.err.println( e.getClass().getName()+": "+ e.getMessage());
}}}

When program is compiled and executed, it will produce the following result:

Connect to database successfully
Authentication:trueCollection created successfully
Collection mycol selected successfully

Insert a document

To insert a document into mongodb, insert() method of com.mongodb.DBCollection class is used.

Code snippets to insert a documents:

import com.mongodb.MongoClient;import com.mongodb.MongoException;import com.mongodb.WriteConcern;import com.mongodb.DB;import com.mongodb.DBCollection;import com.mongodb.BasicDBObject;import com.mongodb.DBObject;import com.mongodb.DBCursor;import com.mongodb.ServerAddress;import java.util.Arrays;publicclassMongoDBJDBC{publicstaticvoid main(String args[]){try{// To connect to mongodb serverMongoClient mongoClient =newMongoClient("localhost",27017);// Now connect to your databases
DB db = mongoClient.getDB("test");
System.out.println("Connect to database successfully");
boolean auth = db.authenticate(myUserName, myPassword);
System.out.println("Authentication: "+auth);
DBCollection coll = db.getCollection("mycol");
System.out.println("Collection mycol selected successfully");
BasicDBObject doc =newBasicDBObject("title","MongoDB").
            append("description","database").
            append("likes",100).
            append("url","http://www.tutorialspoint.com/mongodb/").
            append("by","tutorials point");
         coll.insert(doc);System.out.println("Document inserted successfully");}catch(Exception e){System.err.println( e.getClass().getName()+": "+ e.getMessage());}}}

When program is compiled and executed, it will produce the following result:

Connect to database successfully
Authentication:trueCollection mycol selected successfully
Document inserted successfully

Retrieve all documents

To select all documents from the collection, find() method of com.mongodb.DBCollection class is used. This method returns a cursor, so you need to iterate this cursor.

Code snippets to select all documents:

import com.mongodb.MongoClient;
import com.mongodb.MongoException;
import com.mongodb.WriteConcern;
import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.BasicDBObject;
import com.mongodb.DBObject;
import com.mongodb.DBCursor;
import com.mongodb.ServerAddress;
import java.util.Arrays;
public class MongoDBJDBC{
public static void main(String args[]){
try{// To connect to mongodb server
MongoClient mongoClient =new MongoClient("localhost",27017);// Now connect to your databases
DB db = mongoClient.getDB("test");
System.out.println("Connect to database successfully");
boolean auth = db.authenticate(myUserName, myPassword);
System.out.println("Authentication: "+auth);
DBCollection coll = db.getCollection("mycol");
System.out.println("Collection mycol selected successfully");
DBCursor cursor = coll.find();
int i=1;
while(cursor.hasNext()){
System.out.println("Inserted Document: "+i);
System.out.println(cursor.next()); 
            i++;}}catch(Exception e){System.err.println( e.getClass().getName()+": "+ e.getMessage());}}}

When program is compiled and executed, it will produce the following result:

Connect to database successfully
Authentication:trueCollection mycol selected successfully
InsertedDocument:1{"_id":ObjectId(7df78ad8902c),"title":"MongoDB","description":"database","likes":100,"url":"http://www.tutorialspoint.com/mongodb/","by":"tutorials point"}

Update document

To update document from the collection, update() method of com.mongodb.DBCollection class is used.

Code snippets to select first document:

import com.mongodb.MongoClient;import com.mongodb.MongoException;import com.mongodb.WriteConcern;import com.mongodb.DB;import com.mongodb.DBCollection;import com.mongodb.BasicDBObject;import com.mongodb.DBObject;import com.mongodb.DBCursor;import com.mongodb.ServerAddress;import java.util.Arrays;publicclassMongoDBJDBC{publicstaticvoid main(String args[]){try{// To connect to mongodb serverMongoClient mongoClient =newMongoClient("localhost",27017);// Now connect to your databases
         DB db = mongoClient.getDB("test");System.out.println("Connect to database successfully");boolean auth = db.authenticate(myUserName, myPassword);System.out.println("Authentication: "+auth);DBCollection coll = db.getCollection("mycol");System.out.println("Collection mycol selected successfully");DBCursor cursor = coll.find();while(cursor.hasNext()){DBObject updateDocument = cursor.next();
            updateDocument.put("likes","200")
            col1.update(updateDocument);}System.out.println("Document updated successfully");
         cursor = coll.find();int i=1;while(cursor.hasNext()){System.out.println("Updated Document: "+i);System.out.println(cursor.next()); 
            i++;}}catch(Exception e){System.err.println( e.getClass().getName()+": "+ e.getMessage());}}}

When program is compiled and executed, it will produce the following result:

Connect to database successfully
Authentication:trueCollection mycol selected successfully
Document updated successfully
UpdatedDocument:1{"_id":ObjectId(7df78ad8902c),"title":"MongoDB","description":"database","likes":100,"url":"http://www.tutorialspoint.com/mongodb/","by":"tutorials point"}

Delete first document

To delete first document from the collection, you need to first select the documents using findOne() method and then remove method of com.mongodb.DBCollection class.

Code snippets to delete first document:

import com.mongodb.MongoClient;import com.mongodb.MongoException;import com.mongodb.WriteConcern;import com.mongodb.DB;import com.mongodb.DBCollection;import com.mongodb.BasicDBObject;import com.mongodb.DBObject;import com.mongodb.DBCursor;import com.mongodb.ServerAddress;import java.util.Arrays;publicclassMongoDBJDBC{publicstaticvoid main(String args[]){try{// To connect to mongodb serverMongoClient mongoClient =newMongoClient("localhost",27017);// Now connect to your databases
         DB db = mongoClient.getDB("test");System.out.println("Connect to database successfully");boolean auth = db.authenticate(myUserName, myPassword);System.out.println("Authentication: "+auth);DBCollection coll = db.getCollection("mycol");System.out.println("Collection mycol selected successfully");DBObject myDoc = coll.findOne();
         col1.remove(myDoc);DBCursor cursor = coll.find();int i=1;while(cursor.hasNext()){System.out.println("Inserted Document: "+i);System.out.println(cursor.next()); 
            i++;}System.out.println("Document deleted successfully");}catch(Exception e){System.err.println( e.getClass().getName()+": "+ e.getMessage());}}}

When program is compiled and executed, it will produce the following result:

Connect to database successfully
Authentication:trueCollection mycol selected successfully
Document deleted successfully
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