SpringBoot Inconsistent configuration resolution @ConfigurationProperties vs @Value from environment variables

When using @ConfigurationProperties, the camelCase variable names are resolved correctly from environment variables when they contain an _ character between the camelcase parts.

Version

The issue was discovered on 2.1.5, but also confirmed on 2.4.3.

Details

Given an app with a configuration property props.confValue in the application.yml, if users try to use an the environment value PROPS_CONF_VALUE they resolve to different values if they use @ConfigurationProperties compared to using @Value("props.confValue").

application.yml

props:
  confValue: defaultValue

Using @ConfigurationProperties

@ConfigurationProperties("props")
class ConfigProps {
    var confValue: String? = null
}

Using @Value

@Component
class AutowiredValueBean() {
    @Value("\${props.confValue}")
    lateinit var confValue: String
}

Test cases:

Starting the app with PROPS_CONF_VALUE=envValue results in - ConfigProps.confValue having the value of envValue - AutowiredValueBean.confValue having the value of defaultValue

Starting the app with PROPS_CONFVALUE=envValue results in - ConfigProps.confValue having the value of envValue - AutowiredValueBean.confValue having the value of envValue

A reproduction of the issue can be found here.

Comment From: snicoll

Thanks for the sample.

There's a note in the reference guide about this. Rather than using props.confValue you should be using props.conf-value so that the same rules apply.