If you want to use simple "input" prefix, which is trying to pickup properties form the root, you will need to update your application.properties file content with .properties prefix, like @rahulP suggested.

But, as far as you are trying to map ServiceModel - better will be to update prefix and properties with input.service prefix, see https://docs.spring.io/spring-boot/reference/features/external-config.html#features.external-config.typesafe-configuration-properties:

@ConfigurationProperties(prefix = "input.services")

application.properties:

input.services.default.host=Default
input.services.default.ip=127.0.0.1
input.services.default.desc=Default Desc

input.services.serviceA.host=ServiceA
input.services.serviceA.ip=192.168.21.1
input.services.serviceA.desc=ServiceA Desc

input.services.serviceB.host=ServiceB
input.services.serviceB.ip=192.168.21.22
input.services.serviceB.desc=ServiceB Desc

Also I think you are missing default contructor in ServiceModel, which is required for Spring.