How to make ConfigurationProperties fields mandatory in Micronaut?

Question

I am using ConfigurationProperties to load properties to my application.

@ConfigurationProperties("foo.properties") 
class WaterStreetProperties {    
 lateinit var fooProp: String  
 lateinit var fooProp2: String   
 lateinit var fooProp3: String   
 lateinit var fooProp4: String 
}

I want to make them mandatory and the application should fail if a property is missing. How can I do this?

• Micronaut doesn't want to start if I use data classes.
• It doesn't work if I use final fields to force the properties to be populated.
• Giving value in the constructor doesn't work either.

Answer 1

You may actually use data class with @NotEmpty constraints like shown below as long all fields are mutable (var generates both getter and setter).

@Context causes bean to be loaded into application context during startup. If any validation errors, app will fail during startup.

import io.micronaut.context.annotation.Context
import io.micronaut.context.annotation.ConfigurationProperties
import javax.validation.constraints.NotEmpty

@Context
@ConfigurationProperties("foo.properties") 
data class WaterStreetProperties(
    @field:NotEmpty var fooProp: String = "",  
    @field:NotEmpty var fooProp2: String = "",   
    @field:NotEmpty var fooProp3: String = "",   
    @field:NotEmpty var fooProp4: String = "" 
)

Tested with MN 3.8.7