Difference between Dependency Management and Dependencies in Maven

Maven is a software management tool, use to manage information, dependencies and other things for a project.

It has two mechanisms to add the dependencies of other modules/project. One is Dependencies tag and other is Dependency Managment. People often wonder whats a difference between the two. An important question is when to use what?

First, of all, we should have an idea of what is multi module applications.As in the case in case of multi module applications only they differ.

A multi-module project is, as its name suggests, a project that consists of multiple modules, where a module is a project. You can think of a multi-module project as a logical grouping of sub-projects. The packaging of a multi-module project is “pom” since it consists of a pom.xml file but no artifact (jar, war, ear, etc).


That’s a technical story. But it is not great if we are trying to teach some one. As concepts should be as simple as a story for a 12-year-old child. So let’s understand dependencies and dependency management.

There is a man called Peter, he has two ice cream parlors, Gelatos, and Baskin Robbins. Peter has two children Ron and Seria.

Peter has 2 ice cream in gelatos ice cream parlor – mango[ basic version ] and straberry[ moderate version] and 1 ice cream in Baskin Robbins – black current[high version].

Both Ron and Seria can have all the ice creams which their father has in Gelatos parlor, but they can have ice from Baskin Robbins only if they ask for it.Which means they can only have black current if they ask for specific it, but they don’t have to mention which version of black current they need, as their father Peter already know which kind of black current ice we have.

Here Peter is parent module and,  Ron and Seria are child modules.Gelatos is dependencies tag and Baskin Robin is Dependency Management tag.


So all the dependencies present in dependencies tag will be available to all its child modules.But all the dependencies present in dependency management of parent module will be available to the child only if those dependencies are declared in dependencies tag of child module.

So why are we even using dependency management if dependencies tag passes all the dependency to its children?

  1. As all the children might not need all the dependencies present in parent module, so it is always wise to use Dependency Managment.
  2. Using Dependency Managment we can create a consistency of which version and tag of any artifact which we are using through out the application.[It help to maintain the version of artifact]
  3. Dependency Managment manage version, scope, and exclusion of artifact in child modules.

Example –

Parent POM- A

<pre><?xml version="1.0" encoding="UTF-8"?>
<project xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">



It has 2 child module A and B. Parent A has 3 dependencies in total:-

  • d1 [Inside dependencies tag]
  • d2 [Inside dependency management tag]
  • d3 [Inside dependency management tag]


 Child Pom B

<pre><?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">


It will have access to 3 artifacts

  • d1 [coming from dependencies of parent ]
  • d2 [coming from  parent dependency management as mention in its dependencies tag]
  • d4 [coming from its dependencies tag]

Note:- It will not have the d3 artifact, as d3 is mention dependency management tag of parent pom [POM A] but not present in child pom [POM B].

Child Pom C

<pre><?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">


Similarly, It will have access to 3 artifacts

  • d1 [coming from dependencies of parent ]
  • d3 [coming from  parent dependency management as mention in its dependencies tag]
  • d5 [coming from its dependencies tag]

Note:- It will not have the d3 artifact, as d3 is mention dependency management tag of parent pom [POM A] but not present in child pom [POM B].


Further Reading – http://maven.apache.org/guides/introduction/introduction-to-dependency-mechanism.html


Add Google Authentication using Firebase in React+Redux Application

Single page applications(SPA) are quite famous these days, they are easy to build thanks to all the available libraries and framework. Angular (by Google) and React(by Facebook) are the most famous options available to explore these days. Because of these, front-end applications are now easy to manage and maintain. But even if we are able to create this SPA using all the technologies, we still need some server side logic to persist our data, and most importantly we need authentication so that each user can perform an action in the scope they are authorized to do.

Below is the diagram which shows the authentication flow.


Quick Intro of Firebase

Formerly known as Google Cloud Messaging (GCM), Firebase Cloud Messaging (FCM) is a cross-platform solution for messages and notifications for Android, iOS, and web applications, which currently can be used at no cost.

Today we will try to build a simple SPA using React, Redux, and Firebase(it will provide the google authentication)


Installed Software

We will follow the https://github.com/jainamit333/react_google_authetication to walk through the development.

Branch Name:- vanilla

Create a directory name react-authentication

 mkdir google-authentication-react
 cd google-authentication-react


Create Directory Structure as follows

Screen Shot 2017-08-05 at 2.00.09 PM

Add following code to package.json 

"name": "google-authentication-react",
"version": "0.1.0",
"private": true,
"scripts": {
"start": "npm run build; node server/index.js",
"start-dev": "nodemon server/index.js",
"build": "webpack -p",
"build-dev": "webpack -w",
"build-sass": "node-sass -w ./client/styles/main.scss -o ./client/styles/mainSheet",
"test": "echo \"Error: no test specified\" &amp;amp;amp;amp;amp;amp;&amp;amp;amp;amp;amp;amp; exit 1",
"stats": "webpack --env production --profile --json &amp;amp;amp;amp;amp;gt; stats.json"
"dependencies": {
"axios": "^0.16.1",
"babel": "^6.5.2",
"babel-core": "^6.18.0",
"babel-loader": "^6.2.7",
"babel-preset-es2015": "^6.18.0",
"babel-preset-react": "^6.16.0",
"babel-preset-stage-2": "^6.24.1",
"body-parser": "^1.17.1",
"bootstrap": "^4.0.0-alpha.6",
"css-loader": "^0.28.0",
"express": "^4.15.2",
"firebase": "^4.2.0",
"muicss": "^0.9.20",
"node-sass": "^4.5.2",
"react": "^15.6.1",
"react-addons-css-transition-group": "^15.6.0",
"react-addons-transition-group": "^15.6.0",
"react-dom": "^15.6.1",
"react-redux": "^5.0.4",
"react-router": "^3.0.0",
"react-router-dom": "^4.1.2",
"reactstrap": "^4.8.0",
"redux": "^3.6.0",
"redux-logger": "^3.0.1",
"redux-thunk": "^2.2.0",
"sass-loader": "^6.0.3",
"style-loader": "^0.16.1",
"volleyball": "^1.4.1",
"webpack": "^2.7.0",
"webpack-livereload-plugin": "^0.10.0"
"devDependencies": {
"chai": "^3.5.0",
"cross-env": "^3.1.4",
"expose-loader": "^0.7.3",
"mocha": "^3.1.2",
"nodemon": "^1.11.0",
"react-hot-loader": "^1.3.1",
"supertest": "^2.0.1",
"supertest-as-promised": "^4.0.1",
"webpack-dashboard": "^0.4.0",
"webpack-dev-server": "^2.6.1"

At line number 26 we have added the dependency for firebase.

Note:- This package.json may contain many extra dependencies as I have extracted it from my other project just for tutorial purpose.

Install all the added dependencies

npm install

Add web pack Config code

const path = require('path');
const LiveReloadPlugin = require('webpack-livereload-plugin');
const webpack = require('webpack');

module.exports = {
entry: './client/index.js',
output: {
filename: 'bundle.js',
path: path.resolve(__dirname, 'client/dist')
context: __dirname,
resolve: {
extensions: ['.js', '.jsx', '.json', '*']
devServer: {
inline: true,
contentBase: './dist',
port: 3001
module: {
rules: [{
test: /\.jsx?$/,
exclude: /(node_modules|bower_components)/,
loader: 'babel-loader',
options: {
presets: ['react', 'es2015','stage-2']
test: /\.scss$/,
use: [
plugins: [
new webpack.DefinePlugin({

'process.env.COSMIC_BUCKET': JSON.stringify(process.env.COSMIC_BUCKET),
'process.env.COSMIC_READ_KEY': JSON.stringify(process.env.COSMIC_READ_KEY),
'process.env.COSMIC_WRITE_KEY': JSON.stringify(process.env.COSMIC_WRITE_KEY)
new LiveReloadPlugin({appendScriptTag: true})



React and Redux related files

  • server/index.js
&amp;amp;amp;amp;lt;pre&amp;amp;amp;amp;gt;const express = require('express');
const app = express();
const path = require('path');
const volleyball = require('volleyball');
//serve up static files
app.use(express.static(path.resolve(__dirname, '..', 'client')));
app.use(express.static(path.resolve(__dirname, '..', 'node_modules')));
app.use(function (err, req, res, next) {
    res.status(err.status || 500).send(err.message || 'Internal server error.');

// handle every other route with index.html, which will contain
// a script tag to our application's JavaScript file(s).
app.get('*', function (request, response) {
    response.sendFile(path.resolve(__dirname, '..', 'client', 'index.html'))
//listen on port 3000
app.listen(process.env.PORT || 3000, function () {
    console.log("Rockin' out on port 3000 homie");

We are starting the project on port 3000.

  • redux/actions/actions.js
var constants = {

export default constants;

We have created constants for actions which will be supported for out dummy application

  • redux/actions/auth.js
import constant from './actions'

export const startAuth = keyWord =&amp;amp;amp;gt; {

return {

export const alreadyLogin = response =&amp;amp;amp;gt; {



export const authError = error =&amp;amp;amp;gt; {

return {

export const authSuccess = response =&amp;amp;amp;gt; {
return {

These are the various activities that will be spawn during our login lifecycle.
We usually create a different actions file for a different piece of flow.

  • redux/reducers/auth.js
import constants from '../actions/actions'

const auth = (state = [], action) => {
switch (action.type) {

return Object.assign({}, state, {
authenticated: false,
authenticating: true,
user: action.user
}, ...state)
return Object.assign({}, state, {
authenticated: false,
authenticating: false,
user: {}
}, ...state)
return Object.assign({}, state, {
authenticated: true,
authenticating: false,
user: action.user
}, ...state)

case constants.ALREADY_LOGIN:
return Object.assign({}, state, {
authenticated: true,
authenticating: false,
user: action.user
}, ...state)
return state

export default auth

As you can see, on the success we are setting user and setting param authenticated and authenticating accordingly in every case.
Other two param are mostly if we want to add loading bar during the login process.


  • redux/reducer.js
import {combineReducers} from "redux";
import auth from "./reducers/auth";

const googleBooks = combineReducers({

export default googleBooks

This is the place where we combine all our reducer.
For now, we have only one main reducer which we are adding in line 5.


import { createStore, applyMiddleware } from 'redux';
import reducer from './reducer';
import thunk from 'redux-thunk';
import {createLogger} from 'redux-logger';

const initialState = {

const store = createStore(

export default store;

We are creating a redux store and adding our combined reducer in line 15.

  • client/index.html
<pre><!DOCTYPE html>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1" />
    <title>Books Around You</title>
    			<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css">
    <script src="https://code.jquery.com/jquery-3.2.1.min.js"

    <script src="/dist/bundle.js" defer></script>

<div id="root"></div>


Creating a placeholder for all our react component

  • client/index.js
<pre>import React from 'react';
import ReactDOM from 'react-dom';
import {Provider} from 'react-redux';
import store from '../redux/store';
import Dashboard from "./components/Dashboard";

    <Provider store={store}>
        <Dashboard />

we are adding dashboard component as out main component which will be added to root div

  • client/component/Dashboard.js
<pre>import React, {Component} from "react";
import {connect} from "react-redux";
import Navigation from "./Navigation";
import {login} from "../../services/firebase/auth";
import UserInfoPanel from "./UserInfoPanel";

class Dashboard extends Component {

    componentDidMount() {

    render() {
        return (

                <Navigation />

<div className="mui-row">

<div className="mui-row">



function mapStateToProp(state) {
    return state;

export default connect(mapStateToProp)(Dashboard)</pre>

We are calling login method on component did mount.
So it will check if we are already login or not before mounting this component

  • client/component/Navigation.js
<pre>import React from "react";
import {connect} from "react-redux";
import {login, logout} from "../../services/firebase/auth";

class Navigation extends React.Component {

    render() {

        var styles = {


        return (
            <nav className="navbar navbar-default">

<div className="container-fluid">

<div className="navbar-header">
                        <a className="navbar-brand" href="#" >
                            <span  className="glyphicon glyphicon-bishop " aria-hidden="true" style={styles.baseColor}></span>

<ul className="nav navbar-nav navbar-right ">

                            {this.props.authenticated && <span style={styles.marginTop} onClick={logout} className="btn btn-sm btn-danger">Logout</span>}
                            {!this.props.authenticated && <span style={styles.marginTop} onClick={login(this.props.dispatch)} className="btn btn-sm btn-danger">Login</span>}




function mapStateToProps(state) {
    return {
        authenticated: state.auth.authenticated,

export default connect(mapStateToProps)(Navigation)</pre>

If the user is login LOGOUT button will render another wise LOGIN button.

  • client/component/UserInfoPanel.js
<pre>import React from 'react';
import {connect} from "react-redux";

class UserInfoPanel extends React.Component {

    render() {
        const styles = {
                width: '20em',
                position: 'relative',
                display: 'flex',
                backgroundColor: '#fff',
                border: '1px solid rgba(0,0,0,.125)',
                borderRadius: '.25rem',
        return (

<div className="card" style={styles.card}>
                { this.props.authenticated && <img className="card-img-top img-thumbnail" src = {this.props.user.photoURL} alt="Card image cap"/> }
                { this.props.authenticated &&

<div className="card-block">

<h4 className="card-title">{this.props.user.displayName}</h4>





function mapStateToProps(state) {
    return {

        authenticated: state.auth.authenticated,
        authenticating: state.auth.authenticating,
        user: state.auth.user

export default connect(mapStateToProps)(UserInfoPanel)</pre>

This component is to show the information of the login user.
In highlighted part, you can check we are mapping state param to props of the component.
This is a connected component.

Firebase related Files

  • services/firebase/config.js
import firebase from 'firebase'

const config = {

apiKey: "<your api key from google developer console.>",
authDomain: "<auth domain from firebase project eg >",
databaseURL: "<databse url from firebase>",
storageBucket: "<storage bucket from firebase>",


export const provider = new firebase.auth.GoogleAuthProvider();
export const firebaseAuth = firebase.auth

Replace the config part from your configs.
On line 12 we are initializing firebase.
On line, we are creating a google authentication provider.
Line no 14 states the scope of google api we are using, for now, we only need plus.login,
as we are using only from authentication.
When you need some other access also add other scopes to the same provider in next line.

  • services/firebase/auth.js
import { firebaseAuth, provider} from './config'
import {alreadyLogin, authError, authSuccess, startAuth} from "../../redux/actions/auth";
import store from '../../redux/store'

export function logout () {

return firebaseAuth().signOut()

function doLogin() {

firebaseAuth().signInWithPopup(provider).then(function(result) {

}).catch(function(error) {

export function login () {

firebaseAuth().onAuthStateChanged((response) => {

In login method we are first checking of user is already login or not.
If not it will called do login method otherwise, it will called the action login already.

In doLogin method we are login usingn google provider.
If it is successful we are calling authSuccess action otherwise
authError action.

NOTE:- Since we are using Google authentication from firebase, it has to be enabled in firebase.Inside your firebase project go to authentication, go to sign-in-method and enable google provied.

What Yagni Is?

Often developer debates a lot about what YAGNI is actually. Writing any new piece of code bind developer’s hand in the name of YAGNI.

I have worked in both product base company and service based company.I personally feel that YAGNI is more appreciated in the service based company, as in product based any extra feature is helpful.

People back YAGNI by saying “You don’t wipe before you shit.”.So true.We should not increase the scope of the problem as it may open the gates of new bugs.So YAGNI tells us “don’t write any extra/new code unless it is actually required”.

I agree with the last quoted statement.But should we bind our hands in implementing the requirement in a fashion that it should always be open for extensibility, or to write any functionality in a more generic way so that it can be reused any time in near future?

So, what my definition of YAGNI is: – Always write the code in the scope of the current requirement, but don’t cry out YAGNI if you want to solve it in the generic or extensible way.The code should close for modification but open for extensibility.

Try to solve problems in generic ways, that can be used in future.

MicroService – Brief Introduction

This post will focus on what Microservices are, why is it so famous these days, what are the positive and negative aspects of these services and what all area we will try to cover in future posts.

In addition, will share few youtube links, which are quite helpful to understand this concept. As a developer, I will say it is just one of the way how well we are packaging or modularizing code.

First of all, I would like to tell you, that I am inclined toward MicroServices, so most the things you find here will kind be in favor of these.But I will discuss all the challenges which you might face when you try to follow the awesome journey of MicroServices.

What is Micro Service?

Rather than going for a definition we will try to find the what are the common characteristics of Mirco Services.

In simple terms, you can think of a very small independent project capable of performing all the task.So If in a monolith you have various responsibilities, let each of this responsibility as a separate service.What responsibility does not have any concrete boundary. So this lets to the rise of the new question, how big or how small the micro services should be.Some people says it should be small enough to be handled by one developer, some say it should not be more than then few hundred line of code.To solve this, we will term service as a micro service if they have few of the properties/characteristics mention below.

Characteristics of MicroServices

  • Can be upgraded or rewrite independently.
  • Have fault tolerance and monitoring mechanism.
  • Each service is a complete Product.
  • Should have their own Data Management.
  • Should be easily replacable.
  • Should only expose the endpoint to dependendant services.


What a fuss is this, and Why is it becoming so popular these days?

As we all know that it is simple to solve number of small problems and then join all of them to solve the bigger problem.What we call is devide and conqure. Only problem in this approch is we need a very good merger technique to have a successful solution.With Devops of today(Docker,Kubernets,Mesos) it have been made possible to developer to manage large number of services and there deployment.Even it has helped to increase the resource utilization , which have further decreased the cost of maitaining multiple services.


  • It break the problem into smaller problem, helping developer to solve it more accuratley and in most optimized manner.
  • Partial Deployment and Partial Upgradation of Application is possible.
  • Help to reduce the develoment time.
  • We can easily rewite any service .
  • Services can be written in any programming languages , and we can easily try new progamming language.
  • Easier to find and fix bottleneck in the system.
  • Maintainance and Bug fix can be simper.
  • Test scope increases as we have to test smaller units independently.
  • CI/CD can be implemented easily.
  • Preserve modularity.


  • It increases the Devops activities.
  • Organization have to monotor and handle large number of sevices.
  • Service Discovery and trackng of request can be tidious task.
  • Need change in Oraganization culture.
  • Developer have to work more closely with devops , in order to make the development more stream line.
  • Need advance Devops.
  • Since it is kinda a new, not every one have clear idea what is a baoundary of MiroService.

Some Great Videos to give more insight.


Topics to be cover in upcoming blogs

  • Modules vs Microservices
  • How to share domain between different micro services
  • Should we have a common DAO[Database ] layer for every service or each service should have their own DAO layer?
  • All micro services in single Git Repo or they should have separate Git Repo
  • How to do monitoring of Micro Services.
  • How to track the flow of any particular request in real time between services.
  • Containerization of micro services.
  • Creating an environment of  Containerization service, which is self-deployed.
  • When to go for Micro Services.
  • How to shift from Monolith to Microservices.
  • How to perform Integration testing involving couple of Microservices as dependencies.
  • Distributed logging for Services.

Spring Boot + Docker + Bit Bucket + Automate Deployment

An idea behind this blog to walk through the auto build of docker image in docker hub for Spring boot application.

Note: – This method is not production level, so use it for staging or development phase only.

(Why it is not suitable for production ?)

[As we have to push the jar to the git repository, to reduce few steps.]

Technology Stack Used

  • Spring Boot [1.4.1 Release]
  • Java 8
  • Maven 2
  • Bit Bucket
  • Docker Hub


  • Docker Hub Account
  • Bit Bucket Account
  • Minimum knowledge of Spring boot and Java
  • Link Bit Bucket to Docker Hub. CLICK HERE for the reference.


  1. Create Spring boot Application Capable of creating docker image
    • Create simple spring boot application with web module.[CLICK HERE to create using spring start.io or get it from BIT-BUCKET repo (master branch)].
    • Add Simple test controller to the Spring Project or check out to the branch controller-test.
    • Add Docker support to your current spring boot application or check out to branch docker-support. [To learn how to add docker support to spring boot application you check this blog.]
  2.  Create New Repository and link for auto creation of image
    1. Go to docker hub and click on create -> create automatic build
    2. Click on create Auto-build bit-bucket
    3. Select the desired bitbucket repository
    4. Fill required information and click on create.
    5. Go to build setting and provide the branch name from which image should be created and save changes.
    6. Click on build details, it will be empty right now
    7. Make Some changes in that particular branch and push it to the Origin.
    8. Now again check the build details tab, there will be new entry populated with status queued.
    9. Wait for some time its status will change to building than to success.
    10. Now your docker image is ready to use.
  3. Test created docker image
      1. Now pull the docker image
      2. Run the docker image with command [docker run –name docker.test -d -p 8088:8080 jainamit333/docker.demo:docker-support]
      3. Navigate to http://localhost:8088/docker/test.It will show the desired result.

Now each time user push to anything to branch, new docker image will be created.

Dockerize Spring Boot Application

This blog will help the audience to enable them to create docker image from a Spring boot Application.We have created a Spring Boot with maven.

We have already created the code repository. This repository contain 3 branches

1.Master: – Vanilla Spring Boot with Web Module

2.Controller-Test: – Master with test Rest repository.

3.Docker-Support :- Added docker support to Controller-Test branch


  • Spring Boot Knowledge
  • How to create simple DockerFile

Here we will see what changes are required to add docker support to Spring Boot Application. It is the changes required to create Docker-Support branch from Controller-Test branch.

Changes Required in Pom

We need to add below mention plugin in the pom.


Add DockerFile in the project path

FROM frolvlad/alpine-oraclejdk8:slim
ADD target/docker-0.0.1.jar app.jar
RUN sh -c 'touch /app.jar'
ENTRYPOINT ["java","-Djava.security.egd=file:/dev/./urandom","-jar","/app.jar"]

There are two ways to create a docker image from the current source now.

1.Create docker image using maven plugin [can also be used using Jenkin worklow]

Run the command from project directory:- mvn clean package docker:build

2.Create docker image using docker build command

Run mvn install:- mvn clean install

Create docker image by executing the following command from project directory:

docker build  -t  docker.demo:latest  .

ThoughtWorks-interview experience

Got a call from a consultant,

I am sharing my interview experience for the same with you.

  1. Telephonic [30 mins]
    1. Current Project, and how PMS work internally.
    2. The difference between quick sort and merge sort.
    3. Which sorting did java use internally?
    4. When to user Interface, and Abstract classes.
    5. How to make class Immutable, and if immutable class contain a list, how to handle it.
  2. Coding[With Laptop coding]
    1. Write a program to full fill following problem: two(times(three())) or nested cases also.All the operator should be there.[logic was important].Click Here to get the complete code of this problem
  3. Coding[With Laptop coding]
    1. Write a code to compute the cost of the checkout cart, have many items with quantity, the group of items can have the special price. Every item has there individual price.[Focus on domain design]
  4. F2F Interview
    1. Current project design, architecture, your role.
    2. Difference btw soap and rest service.
    3. Domain design for a ROOM.
    4. Multi-thread simple question,
    5. DB designing simple.
  5. F2F Interview
    1. this was more of a discussion rather than the interview, more related to culture and personality.They will try to understand who you are, what are your goals.Are you  right person or not for ThoughtWorks
  6. F2F Interview
    1. It was related to the 3 pillars that ThoughtWorks build on, and try will try to understand your point of view on various social issues
  7. Aptitude Test
    1. There are around 50 questions, you  have to complete as much as question in 12 min
  8. Logical Test
    1. There are 13 question which have to completed in 1 hour.
A major focus will be given to Domain Design, how the class is created and how the will interact.
OOPS, concepts are important.Name of the classes matter.
If really want to crack Thoughtworks, please check few books.