When building a web app it is useful to be able to:

See a list of all the endpoints in your application, and what controller they map to (similar to a rails routes in the Ruby on Rails framework)
Check on the health of your application
Get other arbitrary info

You might not want to do this with a production version of the application, but during development, it is quite reasonable.

One way to accomplish this is to include the Spring Boot Actuator as one of your dependencies, by including this in your pom.xml

   <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-actuator</artifactId>
   </dependency>

You can then put this in your src/main/resources/applicaion.properties:

management.endpoint.mappings.enabled=true
management.endpoints.web.exposure.include=mappings,health,info

This allows you to visit endpoints called /mappings, /health and /info to get various kinds of information about your application.

These work best if you have loaded a JSON formatter extension to your browser such as JSONView for Chrome or JSONView for Firefox since those will allow you to see the JSON in an easily readable format.

More information