Getting Started with Spring Boot

After reading through job descriptions from a large number of companies while searching for a new position, I noticed that almost every backend role at mid-to-large companies listed "Spring Framework experience preferred." Having briefly touched Spring during my military service and then forgotten about it entirely, I found myself coming back to it once again — what a reunion. With interviews just around the corner, diving deep into Spring's core concepts like AOP and DI felt unrealistic, so I set a modest goal: build a simple bulletin board and ship it.

There are several tutorials out there, but I went with the well-known tutorial by jojoldu, which, though a bit dated, walks you through not just using Spring Boot but actually deploying a live service. Below are the issues I ran into while following along.

Note: I started with STS as my IDE but switched to Visual Studio Code partway through the tutorial — keep that in mind as you read.

Lombok Error

This error occurs in STS when Enable Annotation Processing is not checked. I referred to this issue for the fix.

Error: Red underline on access = AccessLevel.PROTECTED

Add the following import:

import lombok.AccessLevel;

java.lang.NoClassDefFoundError: org/junit/runner/manipulation/Filter

This error means JUnit is missing. You can resolve it by adding the JUnit library through the project settings:

Properties → Libraries → Add Library → JUnit

Problem accessing http://localhost:8080/h2-console

You need to change the JDBC URL from the default value to jdbc:h2:mem:testdb.

LocalDate dependency configuration not updated

Starting from Spring 2, Spring Boot 2.0 ships with Hibernate 5.2.16 (the latest version at the time of writing was Spring Boot 2.0.1). Hibernate 5.2 depends on JPA 2.1 and supports it, but it also partially supports JPA 2.2. JPA 2.2 includes support for JSR-310 — the Date and Time API — so the dependency configuration needs to be updated accordingly.

Test code placed in the main folder instead of the test folder kept causing errors

Always put your test code under the test folder.

The BaseEntity Concept

In Rails, you simply inherit from ActiveRecord and everything is taken care of. In Spring, you need to define your own BaseEntity and have your entities extend it.