Creating custom properties

We have already dabbled with application properties in a couple of places in this book. Remember setting spring.mustache.servlet.expose-request-attributes=true in the application.properties file in Chapter 4, Securing an Application with Spring Boot?

Configuring our application using property files is incredibly handy. While Spring Boot offers many custom properties we can use, it’s possible to create our own!

Let’s start by creating some custom properties. To do that, create a brand new AppConfig class, like this:

@ConfigurationProperties("app.config")
public record AppConfig(String header, String intro, 
  List<UserAccount> users) {
}

This Java 17 record can be described as follows:

• @ConfigurationProperties: A Spring Boot annotation that flags this record as a source of property settings. The app.config value is the prefix for its properties.
• AppConfig: The name of this bundle of type-safe...