Kotlin + Spring: ConfigurationProperties data classes

kotlin-spring-configuration-properties.md

Kotlin + Spring: ConfigurationProperties data classes

Create the application.properties or application.yml file

email:
  from: [email protected]
  to: [email protected]

Create the data class

@ConstructorBinding
@ConfigurationProperties(prefix = "email")
data class EmailProperties(
  val from: String,
  val to: String
)

The data class has to be annoted with two annotations:

1. @ConfigurationProperties to bind the properties in our properties or yml file to this class.
2. @ConstructorBinding because we're using a data class. By default, Spring uses the default constructor and setters to instantiate the class annotated by @ConfigurationProperties, this obviously doesn't work with data classes.

Add configuration for detecting @ConfigurationProperties annotated classes

We need to add some configuration to an existing or new class annotated with @Configuration. In this example, we will use a new class.

@Configuration
@ConfigurationPropertiesScan
class EmailConfiguration

We need only a single annotation: @ConfigurationPropertiesScan. This will enable scanning for any @ConfigurationProperties annotated classes in the current package and any sub-packages.