I have property file application-dev.yml
with content:
spring.profiles: dev
config.some.value:
- ELEMENT1
- ELEMENT2
and another application-staging.yml
with content:
spring.profiles: staging
config.some.value:
- ELEMENT1
- ELEMENT2
- ELEMENT3
so I basically do not know size of list. When I reference this list in main application.yml
like this:
some.value: ${config.some.value}
I get Failed to convert property value of type 'java.lang.String' to required type 'java.util.List' for property 'value'
. How to reference it correctly?
Solution
One way would be to use comma-separated lists in your profiles:
spring.profiles: dev
config.some.value: ELEMENT1,ELEMENT2
spring.profiles: staging
config.some.value: ELEMENT1,ELEMENT2,ELEMENT3
Then you should be able to access it in application.yml
some.value: ${config.some.value}
This solution doesn't require knowing list size upfront.
Explanation
The reason why this is working is described here. Specifically:
YAML lists are represented as comma-separated values (useful for simple String values) and also as property keys with [index] dereferencers, for example this YAML:
servers:
- dev.bar.com
- foo.bar.com
Would be transformed into these properties:
servers=dev.bar.com,foo.bar.com
servers[0]=dev.bar.com
servers[1]=foo.bar.com
In particular this means, that if you specify comma-separated list of strings in application.yml
and define List<String>
as value in @ConfigurationProperties
, spring configuration properties binder will convert that comma-separated list of string to List<Strings>
.