Spring Boot is a module of the Spring Framework. It is used to create stand-alone, production-grade Spring Based Applications with minimum efforts. It is developed on top of the core Spring Framework.

Spring Boot follows a layered architecture in which each layer communicates with the layer directly below or above (hierarchical structure) it.

Before understanding the Spring Boot Architecture, we must know the different layers and classes present in it. There are four layers in Spring Boot are as follows:

Presentation Layer
Business Layer
Persistence Layer
Database Layer

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 i.e., frontend part.

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 Flow Architecture

Now we have validator classes, view classes, and utility classes.
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 one thing: there is no need for DAO and DAOImpl classes in Spring boot.
Creates a data access layer and performs CRUD operation.
The client makes the HTTP requests (PUT or GET).
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 JSP page is returned to the user if no error occurred.

Why Spring Boot?

You can choose Spring Boot because of the features and benefits it offers as given here −

It provides a flexible way to configure Java Beans, XML configurations, and Database Transactions.
It provides a powerful batch processing and manages REST endpoints.
In Spring Boot, everything is auto configured; no manual configurations are needed.
It offers annotation-based spring application
Eases dependency management
It includes Embedded Servlet Container

How does it work?

Spring Boot automatically configures your application based on the dependencies you have added to the project by using @EnableAutoConfiguration annotation. For example, if MySQL database is on your classpath, but you have not configured any database connection, then Spring Boot auto-configures an in-memory database.

The entry point of the spring boot application is the class contains @SpringBootApplication annotation and the main method.

Spring Boot automatically scans all the components included in the project by using @ComponentScan annotation.

Spring Boot Starters

Handling dependency management is a difficult task for big projects. Spring Boot resolves this problem by providing a set of dependencies for developers convenience.

For example, if you want to use Spring and JPA for database access, it is sufficient if you include spring-boot-starter-data-jpa dependency in your project.

Note that all Spring Boot starters follow the same naming pattern spring-boot-starter- *, where * indicates that it is a type of the application.

Examples

Look at the following Spring Boot starters explained below for a better understanding −

Spring Boot Starter Actuator dependency is used to monitor and manage your application. Its code is shown below −

<dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-actuator</artifactId></dependency>

Spring Boot Starter Security dependency is used for Spring Security. Its code is shown below −

<dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-security</artifactId></dependency>

Spring Boot Starter web dependency is used to write a Rest Endpoints. Its code is shown below −

<dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId></dependency>

Spring Boot Starter Thyme Leaf dependency is used to create a web application. Its code is shown below −

<dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-thymeleaf</artifactId></dependency>

Spring Boot Starter Test dependency is used for writing Test cases. Its code is shown below −

<dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-test</artifactId></dependency>

Auto Configuration

Spring Boot Auto Configuration automatically configures your Spring application based on the JAR dependencies you added in the project. For example, if MySQL database is on your class path, but you have not configured any database connection, then Spring Boot auto configures an in-memory database.

For this purpose, you need to add @EnableAutoConfiguration annotation or @SpringBootApplication annotation to your main class file. Then, your Spring Boot application will be automatically configured.

Observe the following code for a better understanding −

import org.springframework.boot.SpringApplication;import org.springframework.boot.autoconfigure.EnableAutoConfiguration; @EnableAutoConfigurationpublic class DemoApplication { public static void main(String[] args) { SpringApplication.run(DemoApplication.class, args); }}

Spring Boot Application

The entry point of the Spring Boot Application is the class contains @SpringBootApplication annotation. This class should have the main method to run the Spring Boot application. @SpringBootApplication annotation includes Auto- Configuration, Component Scan, and Spring Boot Configuration.

If you added @SpringBootApplication annotation to the class, you do not need to add the @EnableAutoConfiguration, @ComponentScan and @SpringBootConfiguration annotation. The @SpringBootApplication annotation includes all other annotations.

Observe the following code for a better understanding −

import org.springframework.boot.SpringApplication;import org.springframework.boot.autoconfigure.SpringBootApplication; @SpringBootApplicationpublic class DemoApplication { public static void main(String[] args) { SpringApplication.run(DemoApplication.class, args); }}

Component Scan

Spring Boot application scans all the beans and package declarations when the application initializes. You need to add the @ComponentScan annotation for your class file to scan your components added in your project.

Observe the following code for a better understanding −

import org.springframework.boot.SpringApplication;import org.springframework.context.annotation.ComponentScan; @ComponentScanpublic class DemoApplication { public static void main(String[] args) { SpringApplication.run(DemoApplication.class, args); }}

So, this brings us to the end of blog. This Tecklearn ‘Spring Boot Architecture and Why Spring Boot is used’ blog helps you with commonly asked questions if you are looking out for a job in Java Programming. If you wish to learn Spring Boot and build a career Java Programming domain, then check out our interactive, Java and JEE Training, that comes with 24*7 support to guide you throughout your learning period. Please find the link for course details:

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Java Fundamentals
Introduction to Java Basics
Features of Java
Various components of Java language
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Installation and IDE’s for Java Programming Language

Installation of Java
Setting up of Eclipse IDE
Components of Java Program
Editors and IDEs used for Java Programming
Writing a Simple Java Program

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Data types, Operations, Compilation process, Class files, Loops, Conditions
Using Loop Constructs
Arrays- Single Dimensional and Multi-Dimensional
Functions
Functions with Arguments

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Object Oriented Programming in Java
Implement classes and objects in Java
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Function Overloading
String Handling –String Class
Java Packages

Exception Handling and Multi-Threading

Exception handling
Various Types of Exception Handling
Introduction to multi-threading in Java
Extending the thread class
Synchronizing the thread

File Handling in Java

Input Output Streams
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File Handling in Java

Java Collections

Wrapper Classes and Inner Classes: Integer, Character, Boolean, Float etc
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Collections: ArrayList, Vector, HashSet, TreeSet, HashMap, HashTable

Java Database Connectivity (JDBC)

Introduction to SQL: Connect, Insert, Update, Delete, Select
Introduction to JDBC and Architecture of JDBC
Insert/Update/Delete/Select Operations using JDBC
Batch Processing Transaction
Management: Commit and Rollback

Java Enterprise Edition – Servlets

Introduction to J2EE
Client Server architecture
URL, Port Number, Request, Response
Need for servlets
Servlet fundamentals
Setting up a web project in Eclipse
Configuring and running the web app with servlets
GET and POST request in web application with demo
Servlet lifecycle
Servlets Continued
Session tracking and filter
Forward and include Servlet request dispatchers

Java Server Pages (JSP)

Fundamentals of Java Server Page
Writing a code using JSP
The architecture of JSP
JSP Continued
JSP elements: Scriptlets, expressions, declaration
JSP standard actions
JSP directives
Introduction to JavaBeans
ServletConfig and ServletContext
Servlet Chaining
Cookies Management
Session Management

Hibernate

Introduction to Hibernate
Introduction to ORM
ORM features
Hibernate as an ORM framework
Hibernate features
Setting up a project with Hibernate framework
Basic APIs needed to do CRUD operations with Hibernate
Hibernate Architecture

POJO (Plain Old Java Object)

POJO (Plain Old Java Object)
Persistent Objects
Lifecycle of Persistent Object

Spring

Introduction to Spring
Spring Fundamentals
Advanced Spring

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