What is Spring Boot?

Spring Boot makes it easy to create stand-alone, production-grade Spring based Applications that you can "just run". We take an opinionated view of the Spring platform and third-party libraries so you can get started with minimum fuss. Most Spring Boot applications need very little Spring configuration.

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

The reference guide includes detailed descriptions of all the features, plus an extensive how to for common use cases.

We will start with understanding what Spring Boot wants to achieve by comparing it with Spring and Spring MVC. Once you understand that, you should be in a good position to start with the building blocks of Spring Boot.

Spring Boot vs. Spring MVC vs. Spring

The most important thing to understand is, Spring Boot does not compete with Spring or Spring MVC. It makes it easy to use them.

Spring Framework

The most important feature of Spring Framework is Dependency Injection. At the core of all Spring Modules is Dependency Injection or IOC — Inversion of Control.
When DI or IOC is used properly, we can develop loosely coupled applications. And loosely coupled applications can be easily unit tested.

Spring MVC

Spring MVC provides a decoupled way of developing web applications. With simple concepts like Dispatcher Servlet, ModelAndView, and View Resolver, it makes it easy to develop web applications

Spring Boot

The problem with Spring and Spring MVC is the amount of configuration that is needed:

<bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">

    <property name="prefix">

        <value>/WEB-INF/views/</value>

    </property>

    <property name="suffix">

        <value>.jsp</value>

    </property>

</bean>

<mvc:resources mapping="/webjars/**" location="/webjars/"/>

Spring Boot solves this problem through a combination of Auto Configuration and Starter Projects. Spring Boot also provides a few features to make building production-ready applications faster.The following article digs deeper and gives you a full-blown comparison between Spring, Spring MVC, and Spring Boot Spring Boot vs. Spring MVC vs. Spring - How do they compare?  

Spring Boot Auto Configuration

Spring and Spring MVC applications have a lot of XML or Java Bean Configuration.Spring Boot brings in a new thought process around this.

Can we bring more intelligence into this? When a Spring MVC JAR is added into an application, can we auto configure some beans?

• How about auto configuring a Data Source if a Hibernate JAR is on the classpath?
• How about auto configuring a Dispatcher Servlet if a Spring MVC JAR is on the classpath?

There would be provisions to override the default auto configuration.Spring Boot looks at :

 a) Frameworks available on the CLASSPATH

 b) Existing configurations for the application.

Based on these, Spring Boot provides the basic configuration needed to configure the application with these frameworks. This is called Auto Configuration. This article explores Auto Configuration in depth.

Quick Start

If you are Java developer you can use start.spring.io to generate a basic project.