Read from MongoDB

In this example you are going to learn how you can read data from MongoDB using DataPipeline.

MongoDB is a NoSQL based database that stores the data in the form of collections consisting of documents (or objects). Since it is an extension of the popular key-value database model, it is a preferred database for many in comparison to SQL based relational databases.

Java Code Listing

package com.northconcepts.datapipeline.examples.cookbook;

import java.io.OutputStreamWriter;

import com.northconcepts.datapipeline.core.DataReader;
import com.northconcepts.datapipeline.core.DataWriter;
import com.northconcepts.datapipeline.csv.CSVWriter;
import com.northconcepts.datapipeline.job.Job;
import com.northconcepts.datapipeline.mongodb.MongoReader;

public class ReadFromMongoDb {
    
    public static void main(String[] args) {
        String database = "datapipeline";
        String collection = "clients";

        DataReader reader = new MongoReader(database, collection);
        DataWriter writer = new CSVWriter(new OutputStreamWriter(System.out));
        
        Job.run(reader, writer);
    }
    /* CSV output to console
        Account,LastName,FirstName,Balance,CreditLimit,AccountCreated,Rating
        101,Reeves,Keanu,9315.45,10000.00,1/17/1998,A
        312,Butler,Gerard,90.00,1000.00,8/6/2003,B
        868,Hewitt,Jennifer Love,"0",17000.00,5/25/1985,B
        761,Pinkett-Smith,Jada,49654.87,100000.00,12/5/2006,A
        317,Murray,Bill,789.65,5000.00,2/5/2007,C
     */
}

Code Walkthrough

1. Beginning the execution, database and collection are initialized for the locally installed MongoDB.
2. A DataReader is created from the MongoReader where the constructor MongoReader(database,collection) picks up the data through passed arguments collection and database.
3. A DataWriter is initialized from the CSVWriter class to display output as CSV based data.
4. Finally, the reader and writer are passed to Job.run() method which displays the output on the console.

Console Output

Account,LastName,FirstName,Balance,CreditLimit,AccountCreated,Rating
101,Reeves,Keanu,9315.45,10000.00,1/17/1998,A
312,Butler,Gerard,90.00,1000.00,8/6/2003,B
868,Hewitt,Jennifer Love,"0",17000.00,5/25/1985,B
761,Pinkett-Smith,Jada,49654.87,100000.00,12/5/2006,A
317,Murray,Bill,789.65,5000.00,2/5/2007,C