I'm trying to make a configuration data class in Kotlin with Spring Boot. I have the following class:

@Configuration
@ConfigurationProperties(prefix = "spring.braintree")
data class BraintreeConfigProperties(
    val merchantId: String = "",
    val publicKey: String = "",
    val privateKey: String = "",
    val environment: Environment = Environment.SANDBOX
)

And the following properties:

spring.braintree.merchantId=${BRAINTREE_MERCHANT_ID}
spring.braintree.publicKey=${BRAINTREE_PUBLIC_KEY}
spring.braintree.privateKey=${BRAINTREE_PRIVATE_KEY}

When I run the application I get the following exception:

APPLICATION FAILED TO START
***************************

Description:

Failed to bind properties under 'spring.braintree' to com.x.ps.config.BraintreeConfigProperties$$EnhancerBySpringCGLIB$$311e0531:

    Property: spring.braintree.merchant-id
    Value: ${BRAINTREE_MERCHANT_ID}
    Origin: class path resource [application.properties] - 5:29
    Reason: java.lang.IllegalStateException: No setter found for property: merchant-id

Action:

Update your application's configuration

However, I also have a class which is exactly the same as the BraintreeConfigProperties class. This class (DatabaseConfigProperties) does work. They are completely identical.

What I've tried:

1. Checked if the property names actually match with the configuration names.
2. Tried all three configuration properties separately.
3. Attached a non environment variable with value 1234 to the merchantId property which results in the following exception:

APPLICATION FAILED TO START
***************************

Description:

Failed to bind properties under 'spring.braintree' to com.x.ps.config.BraintreeConfigProperties$$EnhancerBySpringCGLIB$$62509e61:

    Property: spring.braintree.merchant-id
    Value: 1234
    Origin: class path resource [application.properties] - 5:29
    Reason: java.lang.IllegalStateException: No setter found for property: merchant-id

Action:

Update your application's configuration

CodePudding user response：

The proplem here ist that val is final and var can be changed. So you should change your properties to var.

More Info here: https://medium.com/mindorks/kotlin-series-val-vs-var-difference-android-kotlin-ecad780daeb7