Using multiple SpringBootApplications in one Spring Boot project

Right now, I’m spending some of my free time getting up to speed with Spring Boot. Opinionated frameworks like Spring seem like they’d be a great way to build some quick prototypes for some ideas I’ve got bouncing around my head without having to go through the learning curve a whole new language. I’m already overwhelmed enough with my operations (Linux, networking, security, application servers, etc) and Unity automation for work. And now I’m throwing some AWS into the mix for some side work with a friend.

In my experimentation with Spring Boot, I threw together a quick cat fact web service. Running mvn spring-boot:run and accessing the endpoint at http://localhost:8080/getcatfact returns some super-simple JSON with a random cat fact. Yay kitties!

I created another package, based on the Spring Boot tutorial, designed to be a “Hello, World” example. When I run the application, everything starts up fine, and the Cat Fact endpoint still works. But trying to access the http://localhost:8080/greeting endpoint results in a weird “White Label Error Page”. After some internet searching, I found a decent answer. It seems the error is related to having my packages at the wrong level. Spring will search for and load Boot applications at the initial application’s package level and any sub-packages. Since the net.bencarson.catfact and net.bencarson.hello packages were siblings and didn’t share a parent, it was obvious how to fix my problem. I just needed to create a common parent SpringBootApplication and package and move these existing applications underneath.

I created a new class for net.bencarson.services.MyServicesApplication and moved the catfacts and hello packages under the new net.bencarson.services package, the application was still throwing the White Label error for ‘greeting’.

Proper application hierarchy for Spring Boot
Moved the Spring applications under a parent package and application

The final piece I was missing was that I needed to modify my pom.xml. Inside, I had to change the <start-class> element.

<start-class>net.bencarson.services.MyServicesApplication</start-class>

Now the service starts correctly and both ‘catfacts’ and ‘greeting’ endpoints are accessible!

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