Allow injecting dynamic config to ApolloConfigChangeListener

[anandjoshisn]

Is your feature request related to a problem? Please describe.
The annotation ApolloConfigChangeListener takes an array of string (values = String []), which means if I have some namespaces defined in an application.yaml as comma separated values, I can't inject it as it needs to be constant.

Describe the solution you'd like
Either of the two solutions are fine

1. Allow spring expression evaluation. eg - @ApolloConfigChangeListener("#{'${prop.apollo.namespaces:}'.split(',')}")
2. Provide an optional argument. eg - @ApolloConfigChangeListener(namespaces = "${prop.apollo.namespaces}")

Here my application.yaml would be

prop:
  apollo:
    namespaces: "foo,bar,other-namespace"

PS - I can share a sample PR if I can have permission on this repo.

[anandjoshisn]

PR for adding the requested feature - #9

[nobodyiam]

I believe apollo-client already supports the use of placeholders like @ApolloConfigChangeListener("${prop.apollo.namespaces}"), see apolloconfig/apollo#3349.

So the proposed feature is to

1. support the Spring expression
   • I'm not sure whether this is a strong requirement since Spring expression is not commonly used in my experience
2. support configuring a list of namespaces as a placeholder
   • This could be a good feature, what do you think @Anilople ?

[anandjoshi91]

Thanks @nobodyiam for your feedback. As per your suggestion I have opened PR for point 2 - #11