Introduction to Spring Boot

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adessoTurkey

7 min readJun 26, 2021

Spring Boot is a project that is built on top of the Spring Framework. It provides an easier and faster way to set up, configure, and run both simple and web-based applications.

It is a Spring module that provides the RAD (Rapid Application Development) feature to the Spring Framework used to create a stand-alone Spring-based application that you can just run because it needs minimal Spring configuration.

As summarized in the below figure, Spring Boot is the combination of Spring Framework and Embedded Servers.

How did Spring Boot originate?
The Spring framework has gained the interest of the Java developer’s community as a lightweight alternative to EJB and became one of the most popular application development frameworks.

It consists of a large number of modules providing a range of services including a component container, ASP support, security framework, data access framework, web application framework, support classes for testing components and etc.

Collecting all the required spring components together, setting up library dependencies in gradle/maven, and then configuring the required spring beans using xml, annotations, or java code requires quite an effort within the Spring framework.

This is where the Spring Boot Project comes into play!!!

Spring boot is already a launchable app. Depending on what Spring launcher class you extend, it might be a cli app or a web app. To add more stuff to the app you just have to add dependencies to the project. That’s it…

Spring Boot Architecture

In Spring Boot, there is no requirement for XML configuration (deployment descriptor). It uses convention over configuration software design paradigm which means that it decreases the effort of the developer.

The main goal of Spring Boot is to reduce development, unit test, and integration test time and leveraging the following features:

Create stand-alone Spring applications
Embed Tomcat, Jetty, or Undertow directly (no need to deploy WAR files)
Provide opinionated ‘starter’ POMs to simplify your Maven configuration
Automatically configure Spring whenever possible
Provide production-ready features such as metrics, health checks, and externalized configuration
Absolutely no code generation and no requirement for XML configuration

Spring Boot follows a layered architecture in which each layer communicates with the layer directly below or above (hierarchical structure) it. The below diagram demonstrates that every layer of a Spring Boot application is directly communicating with the layer just below or above it is due to the workflow.

Presentation Layer: The presentation layer handles the HTTP requests, translates the JSON parameter to object, and authenticates the request, and transfer it to the business layer. In short, it consists of views.
Business Layer: The business layer handles all the business logic. It consists of service classes and uses services provided by data access layers. It also performs authorization and validation.
Persistence Layer: The persistence layer contains all the storage logic and translates business objects from and to database rows.
Database Layer: In the database layer, CRUD (create, retrieve, update, delete) operations are performed.

Spring Boot uses all the modules of Spring-like Spring MVC, Spring Data, etc. The architecture of Spring Boot is the same as the architecture of Spring MVC, except for one thing: there is no need for DAO and DAOImpl classes in Spring boot. As a summary, in a simple spring boot flow:

Data access layer gets created and CRUD operations are performed.
The client makes the HTTP requests.
The request goes to the controller, and the controller maps that request and handles it. After that, it calls the service logic if required.
In the service layer, all the business logic performs. It performs the logic on the data that is mapped to JPA with model classes.
A response page is returned to the user if no error occurs.

Spring Boot Annotations
Spring Boot Annotations is a form of metadata that provides data about a program. Spring Boot Annotations are mostly placed in the following packages:

org.springframework.boot.autoconfigure
org.springframework.boot.autoconfigure.condition

Detailed information is given on the follow-up blog → Basic Spring & Spring Boot Annotations

Spring Boot Components
The Spring Boot Project provides four key features to begin with and these can be considered as the reason behind Spring Boot’s magic.

Spring Boot Starters
Automatic configuration
Spring Boot CLI
Spring Boot Actuator

Detailed information is given on the follow-up blog → Spring Boot Components

Spring Boot CLI
Spring Boot also provides a command-line tool that can be used to quickly write Spring applications. You can run Groovy scripts with Spring Boot CLI. Groovy code has almost zero boilerplate code compared with Java.

The Spring Boot documentation says:
“You don’t need to use the CLI to work with Spring Boot but it’s definitely the quickest way to get a Spring application off the ground.”

Spring Boot’s CLI gives you more free time from having to add starter dependencies and auto-configuration to let you focus only on writing your application-specific code.
What about dependent libraries? We don’t have Maven or Gradle here. CLI is smart; it detects classes being used in your application and it also knows which Starter dependencies should be used for these classes; accordingly, Spring Boot CLI adds dependencies to the classpath to make it work.
As Spring Boot CLI adds dependencies, a series of auto-configuration kicks in and adds the required bean method configuration so that your application is able to respond to HTTP requests.
CLI is an optional feature of Spring Boot; it just allows you to write a complete application with your application code only as, it doesn’t need to build a traditional project. CLI provides tremendous power and simplicity for Spring development.

Spring Boot Actuator
There are a lot of frameworks that provide tools for application development. But Spring Boot doesn’t only provide application development-specific features; it also provides post-production features. This allows you to monitor your Spring application during production using HTTP endpoints or with JMX.
Other parts of Spring Boot’s building blocks simplify Spring development; the Actuator instead offers the ability to inspect the internals of your application at runtime.
The Actuator provides data on auditing, metrics, and the health of your Spring Boot application using HTTP endpoints or with JMX. It helps you to manage your application when it’s in production.

The Actuator installed in a Spring Boot application provides the following benefits:

It provides details of all beans configured in the Spring application context
It also ensures all environment variables, system properties, configuration properties, and command-line arguments are available to your application
The Actuator gives various metrics pertaining to memory usage, garbage collection, web requests, and data source usage
It provides a trace of recent HTTP requests handled by your application
It also gives information about the current state of the threads in the Spring Boot application

Now that we have gone through the very basics of spring boot let’s take a look at its advantages and disadvantages.

Advantages

Simplified & version conflict-free dependency management through the starter POMs.
We can quickly set up and run standalone, web applications, and microservices.
Reduces the time spent on development and increases the overall efficiency of the development team.
Helps to avoid all the manual work of writing boilerplate code, annotations, and complex XML configurations. The beans are initialized, configured, and wired automatically.
Facilitates the creation and testing of Java-based applications by providing a default setup for unit and integration tests.
You can just assemble the jar artifact which comes with an embedded Tomcat, Jetty, or Undertow application server and you are ready to go.
The Spring Initializer provides a project generator to make you productive with a certain technology stack from the beginning.
The integration of Spring Boot with the Spring ecosystem which includes Spring Data, Spring Security, Spring ORM, and Spring JDBC is easy.
Provides many plugins that developers can use to work with embedded and in-memory databases smoothly and readily.
Allows for easy connection with database and queue services like Oracle, PostgreSQL, MySQL, MongoDB, Redis, Solr, ElasticSearch, Rabbit MQ, ActiveMQ, and many more.
Offers easy access to Command Line Interface which makes the development and testing of Spring Boot apps built with Java or Groovy agile.

Disadvantages

Spring boot may unnecessarily increase the deployment binary size with unused dependencies.
If you are a control freak, I doubt Spring Boot would fit your needs.
Spring Boot sticks well with microservices. The Spring Boot artifacts can be deployed directly into Docker containers. In large and monolithic applications it is not encouraged much.
If you have never worked with Spring before and want to learn about proxies, dependency injection, and AOP programming, it is not recommended to start with Spring Boot because it will make you miss many concepts that you would grasp if you had started using them independently.
You really have to understand a lot of the underlying Spring systems (and a bit of Spring history too), along with some advanced topics in order to modify and troubleshoot it.

***********Thank you for reading************ **********************************************

References

Introduction to Spring Boot

Written by Revda Uluışık