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Mastering Spring Boot in 5 Stages

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Spring Boot is the most popular framework in the Java world to build enterprise applications. Also, Spring Boot is the most sought-after skill to get hired as a Java developer.

Here is my recommended approach to learn Spring Boot.

1. Prerequisites: What you should already know

  1. If you are completely new to Java, then directly jumping on to Spring Boot is NOT recommended.
  2. First, learning Core Java and get familiar with Java ecosystem.
  3. Get familiar with the installation of JDK and using the build tools like Maven or Gradle.
  4. Get familiar with using IDEs like IntelliJ IDEA, Eclipse/STS, VS Code

2. If you are new to Spring itself

Spring Boot is an opinionated framework built on top of various Spring portfolio projects.

So, if you are completely new to Spring itself, I would recommend first to learn a few Spring Core concepts:

  • Dependency Injection
  • Spring Bean Configuration
  • Bean Scopes
  • Aspect Oriented Programming (AOP)

Resources:

You don’t have to master every detail of these concepts in-depth. But having a decent understanding of these concepts will make it easy to understand Spring Boot.

3. You are familiar with Spring framework and want to learn Spring Boot

Once you are familiar with Spring core concepts, then you can begin your journey to learn Spring Boot.

Important Note:

Spring Boot is an opinionated framework built on top of various other Spring projects with convention-over-configuration approach. So, if you are not familiar with underlying technologies such as JPA/Hibernate, Kafka, etc then Spring Boot looks like magic.

While learning as a beginner, you may have to proceed further without understanding how exactly things work behind the scenes. Once you got it working, you may have to go back and explore further how Spring Boot auto-configuration makes it working.

Stage 1: Master Spring Boot Basics

In Stage 1, you learn the fundamentals of Spring Boot.

  • Getting Started with Spring Boot: Learn how to create a Spring Boot application and build a basic HelloWorld style REST API. Then learn how to run the Spring Boot application.

  • Build a basic CRUD REST API: Create a basic REST API performing CRUD(Create, Read, Update, Delete) operations using a HashMap based storage. The goals of this exercise are:

    • Get familiar with how to implement API handler methods for different types of HTTP methods using @GetMapping, @PostMapping, @PutMapping, @DeleteMapping annotations.
    • Understand how to use @PathVariable, @RequestBody to work with URL path variables, HTTP request body.
    • To keep it simple, store the data in a HashMap with key as primaryKey and object as the value.

  • Understand Spring Boot Core Features: Spring Boot provides some features out of the box which are commonly used in building web and enterprise applications.

    • Spring Boot Logging: Spring Boot automatically provides logging support with SLF4J and Logback. You may want to configure it to suit your application needs. So, you need to understand how to customize the default logging configuration.

    • Spring Boot Application Configuration: Spring Boot provides support for providing the application configuration properties in a wide variety of ways. But you mostly like will be using three or four approaches to provide default configuration and overriding the configuration.

    • Spring Boot Profiles: Profiles is a concept in Spring framework which helps in configuring the application differently for different environments. In real projects, you typically want to configure your application with different property values for different environments (dev, qa, prod). You can use Spring profiles to customize/configure your application per-environment and enable the desired profile when starting the application. Spring Boot makes is easy to use profiles with some default conventions.

    • Spring Boot Testing: Testing is an integral part of any professional software development. Spring Boot provides excellent support for testing.

      • Spring Boot Testing Tutorial: This tutorial will give an overview of Spring Boot’s testing support. But when you use databases or Kafka, etc then you can use the Testcontainers library for testing. You can learn this in the next stage.

After completing these tutorials, you should have a good grasp on Spring Boot basics.

Stage 2: Learn to build REST APIs using Database

In Stage 2, you learn how to work with SQL databases, how to handle database transactions, how to test your application when using a database. You should also learn how to handle exceptions gracefully. Finally, you will learn some best practices while building REST APIs using Spring Boot.

Prerequisites:

  • You should be familiar with JDBC if you want to use JdbcTemplate or JdbcClient
  • You should have at least some basic knowledge of JPA if you want to use Spring Data JPA

Spring Boot provides higher-level abstractions to make it easy to work with Databases. You can use newer JdbcClient or older JdbcTemplate to execute SQL queries without writing low-level boilerplate code.

Database transaction management is a crucial part of any real world application using an SQL database. Spring Boot makes it straightforward to apply transaction boundaries using @Transactional annotation. But it is crucial to understand how the transaction management works to avoid some common gotchas.

In real world projects, it is highly recommended to use database migration tools like Flyway or Liquibase to apply any database changes. Again, Spring Boot makes it very straightforward to use those database migration tools with it’s auto-configuration support.

JPA/Hibernate is the most popular ORM library in Java. Spring Data JPA provides a higher-level abstraction on top of JPA that simplifies performing CRUD operations, pagination, etc.

Before learning Spring Data JPA, I highly recommend learning JPA basics of how to configure entities. To keep it simple, you can focus on working with a single entity without any OneToMany, ManyToOne, ManyToMany relations.

This is the right time to learn some best practices while building REST APIs such as following REST API conventions, using proper status codes, etc. Also, now is the right time to learn how to test REST APIs by writing integration tests or repository tests by using Testcontainers.

It’s very important to handle exceptions and return meaningful responses in case of failures. Spring Boot provides different approaches to handle exceptions.

To learn more about testing the Spring Boot applications, you can refer the following resources:

To learn more about JPA/Hibernate and Spring Data JPA:

By now, you should have good enough knowledge to build a REST API backing with a database in a professional way.

Stage 3: Learn Spring Security

In Stage 3, you can learn Spring Security, Event Handling, and Job Scheduling.

Securing the web application or REST APIs is a very common requirement. Spring Security is a highly configurable, customizable framework for implementing security. The “highly configurable and customizable” nature of Spring Security also comes with a steep learning curve.

TIP:

Securing microservices using OAuth 2 is an advanced concept which you can learn in the next stage(s).

Publishing and consuming events is a good practice to decouple the producer and consumer. Spring provides support for publishing and consuming events using an annotation-based programming model.

Running background jobs is another common requirement in enterprise applications. Spring Boot provides job scheduling feature out of the box, but also supports integration with Quartz and JobRunr.

Stage 4: Learn building microservices and securing them with OAuth 2

In Stage 4, you can focus on learning how to build microservices and secure them with OAuth 2.

By now you know how to build a monolithic application using Spring Boot. Now, you can focus on building microservices using Spring Boot, Spring Cloud, etc.

Stage 5: Explore how things work behind the scenes

In stage 5, you can try to understand how things work behind the scenes. The most important part of Spring Boot is “Auto Configuration”, which many people call as “magic”.

Spring Boot auto-configuration is nothing but @Conditional feature on steroids. You can read How SpringBoot AutoConfiguration magic works? article to understand Spring Boot AutoConfiguration.

At this point of time, you can focus on what is required for your project and be able to use them with Spring Boot. Your project may be using Kafka, RabbitMQ, Spring Batch, etc. With the knowledge you gained by now, you shouldn’t have a problem in learning how to integrate them with Spring Boot.

At this stage, I would recommend focusing on learning Architecture concepts.

Learning Resources

Summary

Spring Boot is a powerful framework aimed to make Java enterprise application development easy. Spring Boot provides integration support for everything under the sun either by official starters or community implemented starters.

So, expecting to master Spring Boot in a few hours or in a couple of days is unrealistic. It’s going to take some time. Luckily, you don’t have to learn everything that Spring Boot offers.

If you reach Stage 3, you are good to apply for jobs looking for Spring Boot skills and learn more on the job.

I hope these resources and guidelines help you to lear Spring Boot.

Happy learning!

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