Before jumping into what Spring Boot is, we first need to discuss Spring and the Java ecosystem circa 2003.
Spring - Open Source to the Rescue
Java was in a rough state is 2003.
Sun Microsystems was struggling to keep their core Java libraries up to date and expand its feature set.
IBM provided a lot of these additional libraries and features to help enterprises wanting to use
Java’s ‘Write Once, Run Anywhere’ approach to software.
One of those libraries that is important to our story is ‘Enterprise Java Beans’, or EJB for short.
EJB is a Java API developed by IBM in the late 90’s to modularize construction of applications.
It was a go-to framework for enterprises needing to build Java applications.
EJB had a lot of issues: it was complicated to onboard, difficult to change, and all around a pain to work with.
It also came with a caveat of not having a standardized approach to its usage. This was often locked behind a paid service subscription
from IBM or buying their ready-made software.
In 2003, the concept of ‘Inversion of Control’ was becoming a
well-defined pattern.
IBM utilized it in their EJB implementations, but was never a core concept of the framework and was limited in scope to
the EJB session bean.
Spring brought ‘Inversion of Control’ to the masses, no IBM required.
It was fully open source, and its revolutionary IoC Container automated all the dependency injection. Spring was just significantly simpler to use in comparison to EJB.
Soon Spring expanded their framework to include other helpful libraries that the core Java and IBM frameworks were lacking:
| Spring Library | Description |
|---|---|
| Spring MVC | API for developing ‘Model, View, Controller’ web application patterns. |
| Spring JDBC | Universal database access API. |
| Spring Security | Libraries to secure your java application. |
| Spring ORM | Object relation API that can transform database tables into java objects. |
| Spring Test | Standardized API for testing applications. |
However, Spring soon had a similar problem that IBM ran into.
Tons of customers were using Spring, but they were all implementing it in different ways.
How can the Spring Team help customers when they are all using different approaches to implementing Spring?
The answer was the concept of ‘Convention over Configuration’, and eventually the birth of the Spring Boot library.
Spring Boot - The Opinionated way to Spring
Spring Boot provides an opinionated way of developing Spring applications that fosters well tested code in a fast and easy way.
It was made by developers to make development easy, and it should come as no surprise that using Spring without Spring
Boot is infinitely more difficult.
It extends the Spring framework by providing:
- ‘starters’ that give an ‘Out of the Box’ approach to adding features to an application.
- Auto-configuration API that provides the mechanism for developing your own ‘starters’
- An embedded server for application deployment to help alleviate configuration complexity. (Make JAR not WAR!)
- Hooks for externalizing configuration.
- Metrics to tune and debug your application.
- Health Check concept to see if your application is running successfully or failing.
Spring Cloud - Pulling it All Together
Over the last 20 years, Spring and Spring Boot has created a wave of new development in the Java space.
But how do these all of these new Spring Boot applications get configured and communicate with each other?
The Spring Teams answer was Spring Cloud, which provides a suite of applications and libraries to facilitate communication and configuration between Spring Boot microservices.
These applications and libraries include:
| Spring Cloud Library | Description |
|---|---|
| Config Server | Configuration centralization and management. |
| Discovery Server | Discovering/registering of applications in a cloud ecosystem. |
| Gateway Server | Centralized routing and rerouting service to manage multiple service endpoints. |
| Load Balancing | Load balancer to ensure horizontally scaled applications are properly served without overwhelming one over the other. |
| Circuit Breakers | Quick fail library to prevent cascade failures when function/web calls fail. |
| Distributed Messaging | libraries to simplify cross cloud communication. |
Conclusion - and Birds Eye View
- Java was struggling in 2003 to maintain its current code base and update new feature sets.
- IBM stepped in and created EJB libraries to help companies finding core Java lacking.
- Spring created a framework to make Dependency Injection trivial to compete with EJB by IBM.
- Spring expanded to included API’s for core features missing in the base Java API.
- Spring Boot created an implementation of ‘Convention over Configuration’ for the Spring Framework.
- Spring Cloud created a set of applications and libraries to facilitate configuration and communication between Spring Boot applications in a distributed systems.
That about covers it for today! I’ll be covering more of Spring, Spring Boot, and Spring Cloud in upcoming articles throughout the year, stay tuned!