A Simple Read/Write Example using MongoDB and Java

In this post, we take a look at basic CRUD (Create Read Update Delete) operations on MongoDB using Java JDBC.

We only use Eclipse IDE.

To find out more about NoSQL databases, look here.

MongoDB is a scalable, high-performance open source, schema free, Document-oriented NoSQL database and is highly suitable for Web Applications.

To find out more on MongoDB, refer its home site here.

• Download and Install MongoDB from here.
• Extract the files.
• Run the mongod.exe file present in the bin folder of the Mongodb folder to start the server.
• If you want to open the UI for the database, run the mongo.exe file present in the bin folder.
• You will be needing a mongo.jar file to connect Java to the MongoDB which can be downloaded from here.
• This jar file is also available in the Project Dump which is available for download below. It is present in the folder titled 'JarFiles' in the Project Directory.
• Be sure to add this jar file to the class path.

The code which performs all the CRUD operations is as follows.

package com.examples.mongodb;

import com.mongodb.BasicDBObject;
import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.DBCursor;
import com.mongodb.Mongo ;

public class MongoDBExample {

  public static void main(String[] args) {
  
   try {
    // Mongodb Database Setup
    Mongo m = new Mongo("localhost", 27017) ;
    DB db = m.getDB("authDB") ;
    DBCollection col = db.getCollection("authCollection") ;
  
    // Creating Data 
    // setup and insert data into the authDB database

    BasicDBObject doc = new BasicDBObject() ;
    doc.put("username", "admin") ;
    doc.put("password", "admin") ;
    System.out.println(doc);
    col.insert(doc) ;
   
    // 5 records  are inserted in the following 'for' loop
    for (int i = 0 ; i < 5 ; i++) {
     BasicDBObject data = new BasicDBObject() ;
     data.put("username", "user_" + i ) ;
     data.put("password", "pass_" + i ) ;
     System.out.println(data);
     col.insert(data) ;
     data.clear() ;
    }
    System.out.println("Data Inserted");
   
    // Retrieving Data 
    System.out.println("Data Retrieved");
    DBCursor cursor = col.find() ;
    while (cursor.hasNext()) {
     // The entire records in the collection is displayed here.
     System.out.println(cursor.next());
    }
    

    // Updating Data 
    BasicDBObject oldData = new BasicDBObject() ;   
    oldData.put("username", "admin") ;
    oldData.put("password", "admin") ;
   
    BasicDBObject newData = new BasicDBObject() ;
    newData.put("username", "administrator") ;
    newData.put("password", "administrator") ;
    col.update(oldData, newData) ;
    System.out.println("Data Updated");
   
    DBCursor cursor1 = col.find() ;
    while (cursor1.hasNext()) {
     // The updated record with other records present in the collection is displayed here.
     System.out.println(cursor1.next());
    }
   
    // Deleting Data 
    // This deletes the record where username equals user_5
    BasicDBObject delRecord = new BasicDBObject() ;
    delRecord.put("username", "user_5") ;
    col.remove(delRecord) ;
    System.out.println("Record Deleted") ;
   
    DBCursor cursor2 = col.find() ;
    while (cursor2.hasNext()) {
     // Here there is no record with username data equals user_5
     System.out.println(cursor2.next());
    }

    // Dropping or deleting entire database
    m.dropDatabase("authDB") ;
    System.out.println("Database deleted/dropped");
    DBCursor cursor3 = col.find() ;
    while (cursor3.hasNext()) {
     //Nothing is displayed here as the database is deleted
     System.out.println(cursor3.next());
    }
   } catch (Exception e) {
    // TODO: handle exception
    System.out.println(e.getMessage()) ;
    e.printStackTrace() ;
   }
  }
}

The screen shot of the output is as follows:

This code is available for download along with the entire project directory here.