Need of the hour: The paradigm shift in technology

There come times when we need to shift from an existing level to the next level reason being to stay ahead in the race or to save self from being obsolete. This is known as Paradigm Shift meaning switching from what you have to a new but feasible level.

And in the world of technology, this shift is nothing but mandatory as every day or the other we see a new, fast, error-proof and cost-effective technology. In this short article, I would like to bring in some such areas where we are shifts rapidly.  This list might grow as is and I urge to keep them listed in the comments!

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PUT or POST – Which one to choose!!!

When we develop a RESTFul application we use the HTTP methods (verbs) to create, modify or access to the resources from the application. So, what are these HTTP methods anyway? They are nothing but defines an action that the HTTP request will perform on the server.  These are the HTTP Verbs available to perform action :

  1. GET
  2. POST
  3. PUT
  4. PATCH
  5. DELETE

Most of these verbs are self-explanatory, right?

But, what about the POST and PUT ??? The most common answer is the POST for creating resources while PUT for updating. However, this is how it is being used but why?

In this article, I would try to explain the difference between POST and PUT…

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Maven: A Brief look…

Every application regardless of small or big or huge we have to follow some procedures or cycles. Configuring these steps manually everytime we need to run that cycle is a very cumbersome job. For example Dependencies Management, Pre-Deployment Validations and Checks etc.

Maven came into existence for the purpose of eliminating most of the manual efforts and automate this process.

What is Maven?

It is well known as “The Build Tool”, but I believe it is more than just “A Build Tool” given the facts of its capabilities, but in this tutorial, we will stick to basics of Maven.

  • Create a Maven Project
  • Understand Build Cycle, Build Phase & Goals
  • Understand POM
  • Understand GroupID and ArtifactID
  • Parent POM Concept; Inheritance & Aggregation
  • Simple Maven Project.

Create a Maven Project: 

This is quite easy so I will save it for the last part of the article while creating a simple project, but for now, let’s understand how it works first!!

Understand Build Cycle, Build Phase & Goals:

Build Cycle(s): As I said before there are lots of procedure we have to follow for a build process and these are coined as “Build Cycle”. A cycle consists of one or more “Build Phase(s)” which runs sequentially and in turn, each phase has being assigned with one or more “Goal(s)”

Ex:

mvn clean dependency:copy-dependencies

Build cycle(s) is defined and can be executed as a whole. It signifies a stage of the build. Example: site – This is a build cycle that is responsible for documentation, clean – This is a build cycle that is responsible for gracefully clean up the maven directory where the compiled code resides and default – This is the default process that controls some of the base functionalities like validating the dependencies and so on…

Each Build Cycle contains sequential phases, we can invoke a phase directly from a build cycle. Build Phase run in a sequential manner, so when we execute a build phase, the phase(s) before that phase are also executed prior to the execution.

mvn install

When this above command is executed, all the phases before “install” are executed prior to that.

Now, Goal(s)… There are the granular level commands present in each build phase. If the Goal is associated with a single phase then we can call it directly else we can use the phase name and then the goal name separated by “:”.

mvn clean dependency:copy-dependencies

Understand POM (Project Object Model): 

This is an XML file that contains the information required by Maven to create the builds, like Project Name, ArtifactID, GroupID, Version, Dependencies, etc. This also defines the different build cycle, phases for building the application. Basically, this contains what and hows for the builds.

This file has to be kept in the root folder of the project and has to be named “pom.xml”. A simple pom.xml would be as follows.

Maven

pom.xml derives some information from the super POM which can be overridden in the pom.xml at the project level as well. Later, we will see how to inherit information from Parent POM to other POMs and also how to aggregate POM into parent POM.

Understand GroupID and ArtifactID:

These tags {<groupId> , <artifactId> and <version>} are like address or unique identifier of POM file. When we create a POM we define

  • Group ID as the organization web domain or if it is a common project we can add the project name as well.
  • Artifact ID is mostly the project name and this is used by Maven for naming the Jar file or War file.
  • A Version is a revision done on the POM/Project.

Parent POM Concept; Inheritance & Aggregation:

As Maven encourages the DRY principle, the capability is available to inherit the common properties from a parent project to sub-projects without repeating the same kinds of stuff. This is known as POM inheritance. Let’s see how to do that:

MavanParent.PNG

Also, there will be the scenario where there will be multiple sub-projects and we might have to aggregate all sub-project’s pom.xml into a parent pom.xml.

MavanModel.PNG

NB: <packaging>pom</packaging> – This means that the parent POM will be packaged as POM and would be used by reference only.

Hint: It would be very difficult to see from which POM the dependencies are pulled in, so to find the effective POM we can use the following command.

mvn help:effective-pom

Before jumping into the code to create a simple maven project with inheritance and aggregation, we will see one more concept in Maven i.e its folder structure.

DirectoryStructure.PNG

Simple Maven Project:

In this simple project, I will create a Maven Project which will be a parent project for another sub-project and in parent project, I will add a common dependency for javax.mail. I will then create a new maven project that will inherit the parent maven project’s pom.xml and have the parent (common) dependencies in it too.

Parent pom.xml

Child

Child pom.xmlParent Child project has the mail.jar dependency as well inherited from the parent even without mentioning the same in dependencies list in the child.

ChildWithDependancies

Hope this help in understanding Maven.

Thanks and Happy Coding,
Sovan

 

Spring Boot – Profiles…

Spring Boot is gaining its popularity like any thing in the present time and I know it will be a persistent player in the coming days as well. It there are some features that every technology has and it is every useful in enterprise applications. I am going to write about one “Profiles”.

What is Profiles ?

Every enterprise application has many environment like

Dev | Test | Stage | Prod | UAT / Pre-Prod

Each environment require certain setting specific to them, For Example, in DEV we do not need to check database consistency always whereas in TEST and STAGE we need to. These environment specific configurations are called as Profiles.

How do we maintain Profiles? 

Simple. Properties files!!
We make properties files for each environment and set the profile in the application accordingly so it will pick the respective properties file. Don’t worry we will see how to set it up.

This article will show how to setup Profiles for Spring Boot Application.

Let’s Start with setting up a Spring Boot Application from Spring Starter.

Screen Shot 2018-09-02 at 12.43.23 AM.png

Next, Import the Project into STS as Maven Project. Below is the project structure.
Screen Shot 2018-09-02 at 12.48.17 AM.pngIn this demo application we will see how to configure different database at runtime based on the specific environment by their respective profiles.

As DB connection is better to be kept in a property file so it remains external to application and can be changed, we will do so. But Spring Boot by default provides just 1 property file (application.properties). So how will we segregate the properties based on environment?

The solution would be to create more property file add “profile” name as suffix and configure Spring Boot to pick the appropriate properties based on the “profile”.

Create 3 more application.properties

  1. application-dev.properties
  2. application-test.properties
  3. application-prod.properties

Of course, application.properties will remain as master properties file but if we override any key in profile specific file the later will gain precedence. 

I will now define DB configuration properties for in respective properties file and add code in DBConfiguration.class to pick the appropriate settings.

Base application.properties

Screen Shot 2018-09-02 at 8.33.25 AM.png

In DEV we will use in-memory database

Screen Shot 2018-09-02 at 8.33.58 AM.png

In TEST, we will be using lower instance of RDS mysql database and in PROD higher instance of mysql database. (It’s price that matters…)

Screen Shot 2018-09-02 at 8.43.08 AMScreen Shot 2018-09-02 at 8.43.23 AM

We are done with properties files, let’s configure in DBConfiguration.class to pick the correct one.

Screen Shot 2018-09-02 at 8.48.41 AM.png

We have used @Profile(“Dev”) to let the system know that this is the BEAN that should be picked up when we set the application profile to DEV. Other two beans will not be created at all.

One last setting, how to let the system know that this is DEV or TEST or PROD?

For doing that we will use the application.properties to use the key as below.

spring.profiles.active=dev

From here, Spring Boot will know which profile to pick . Lets run the application now!!

Profile in DEV mode and in DEV it should pick H2 DB.

Screen Shot 2018-09-02 at 9.05.26 AM.png

Screen Shot 2018-09-02 at 9.07.25 AM

Change the profile to PROD, we will see mysql with HIGH Config for DB should be picked and the message would be overridden with PROD message.

Screen Shot 2018-09-02 at 9.09.29 AMScreen Shot 2018-09-02 at 9.09.44 AM

That’s it!! We just have to change only once at the application.properties to let Spring Boot know which environment the code is deployed and it will do the magic with setting.

Please visit the repository, to access the code to see this happening!!

Happy Coding
Sovan

Netflix Eureka – Microservice – Registry-Discovery

In the headline, we saw three buzzwords.

  1. Microservice
  2. Netflix Eureka
  3. RegistryDiscovery

What is the microservice?

In simple words, microservice(s) are clusters of small applications that work together in coordination to provide a complete solution.

When we say a lot of small application running independently together, then all will have their own URLs and PORTs. In that scenario, it would be very cumbersome to maintain all these microservice to run in synchronization and more importantly on monitoring. Even this problem will increase manifold when we start implementing load balancers.

To solve this issue we need a tool that will monitor and maintain the registry of all the microservice(s) in the ecosystem.

What is Netflix Eureka?

This is a tool provided by Netflix to provide a solution to the above problem. It consists of the Eureka server and Eureka clients. Eureka server is in itself a microservice to which all other microservice(s) registers. Eureka Clients are the independent microservices. We will see how to configure this in a microservice ecosystem.

I will be using Spring Boot to create few microservice(s) which will act as Eureka Clients and a Discovery Server which will be a Eureka Server. Here is the complete project structure.

microservice1

Let’s now discuss the Eureka Discovery Server

This is the Eureka server and for that, we have to include Eureka Dependency in the Project. Below is the pom.xml for eureka discovery server.

microService2

Also, we need to update the properties file for this project to indicate that is a discovery server and not a client.

eureka.instance.hostname=localhost
eureka.client.register-with-eureka=false
eureka.client.fetch-registry=false

To bind the discovery application to a specific port and name the application we need to add the following as well.

server.port=8000
spring.application.name=DiscoveryServer

microService3

One last thing to do is to Annotate the Spring Boot Application to enable this as Eureka Server. To do so we need to add @EnableEurekaServer.

microService4

Boot up the application we will see a UI provided by Eureka to list all the servers that get registered. But at this point we have none!!

microService5

Now, let’s add few microservice(s) into the ecosystem and register them to the discovery server. For this also we need to add dependencies required in each service and register the same to the server. We will see in the details below.

I have created three simple microservice (microservice1, microservice2, microservice3) with Spring Boot and each one running in its own port (8002, 8003 and 8004).

microService6

As a client, it should register itself to the server and that happens in the property file as below.

microService7

And the main application would be annotated with @EnableEurekaClient in each microservice.

microService8

Boot up this application to run in port 8004 and it will automatically register itself to the discovery server. In a similar manner, I have created two more microservice and register the same in the discovery.

microService9

We can see three servers are running in the ecosystem and we can monitor the status of these servers too.

This ease the monitoring of all the servers and there replica in case we have used the load balancer.

I hope this will help get started with using Discovery Server and Clients using Eureka…

Eureka! We are done!!


Reference to the GIT Repository containing the code used for this demo!

Happy Coding!!
Sovan

GIT – The home for source code… #2

Welcome Back!

In the last blog, we saw how to install GIT and get started with it. Here, we will be covering few basic concepts of git, git commands, etc.

What will be covered in this part #2

  1. What is a repository?
  2. How to create a new repository or use an existing one?
  3. How to check the status of the repository?
  4. ….& many more

What is a repository?

A repository is a virtual area where GIT stores the codes and maintain the versions. This can be also thought of as the workplace for GIT. We can create our own repository or clone an existing repository as well.

Initialize a repository in local…

  • To initialize a repository i.e. to create a new repository we will use the “ git initcommand. This is one of the first steps to execute while using GIT.
  • This is a one time command used to create a repository which will create a “ .git directory in the working directory. This contains all the metadata required for git.
  • For the existing project, to make that a GIT repo, navigate to that directory and execute the GIT init command. This will make the working project directory a GIT repository.
  • The .git folder contains much information such as the current HEAD (currently checked out commits), Objects, etc.

Clone a repository to local…

  • To get an existing project from GIT repository to local is known as Cloning a GIT Repository.
  • This syncs all the files on the remote repository (coming next) to a local repository and then we can add and edit files and then push it to the remote repository.
  • $git clone https://username@bitbucket.org/myrepo/project_name.git
  • Once this is successful, subfolders would be created under local repository directory and all the files would be cloned into it.
  • This clone contains files, folders, metadata that GIT requires to maintain the changes made on the repository.

We have seen the two ways have the git workplace ready for use. But will start over again with initializing a new repository and take a deep dive into it.

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GIT – The home for source code…

This article is about the source code versioning tool GIT. It became a direct choice for most of the projects for its ease is using and it is also reliable and faster than its counterpart present in the market. Please begin with some fundamental concepts related to GIT…

What is version control system?

We must have kept versions of our code by one mean or other by keeping the backup of the file, sending in emails so we can get it back later (Be careful! Companies keep an eye on that… 😛 😛 ). Version control systems are technologies rather tools that keep an eye and track the changes we do in our code throughout the lifetime of the project or the products. Editing anything in our codebase asks VCS to save the snapshot permanently which can be fetched later as we need.

What are some of the benefits of version control system…

  • Workflows
  • Versions
  • Developers
  • Histories
  • Automation

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