What You Will Learn during this Step:

Spring Boot vs Spring

Spring is just a dependency injection framework. Spring focuses on the "plumbing" of enterprise applications so that teams can focus on application-level business logic, without unnecessary ties to specific deployment environments.
First half of the 2000 decade! EJBs
EJBs were NOT easy to develop.
Write a lot of xml and plumbing code to get EJBs running
Impossible to Unit Test
Alternative - Writing simple JDBC Code involved a lot of plumbing
Spring framework started with aim of making Java EE development simpler.
Goals
Make applications testable. i.e. easier to write unit tests
Reduce plumbing code of JDBC and JMS
Simple architecture. Minus EJB.
Integrates well with other popular frameworks.

Over the next few years, a number of applications were developed with Spring Framework
Testable but
Lot of configuration (XML and Java)
Developing Spring Based application need configuration of a lot of beans!
Integration with other frameworks need configuration as well!
In the last few years, focus is moving from monolith applications to microservices. We need to be able to start project quickly. Minimum or Zero start up time
Framework Setup
Deployment - Configurability
Logging, Transaction Management
Monitoring
Web Server Configuration

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.
Example Problem Statements
You want to add Hibernate to your project. You dont worry about configuring a data source and a session factory. I will do if for you!
Goals
- Provide quick start for projects with Spring.
- Be opinionated but provide options.
- Provide a range of non-functional features that are common to large classes of projects (e.g. embedded servers, security, metrics, health checks, externalized configuration).