Support tree-structure config source

[Emily-Jiang]

From Tomas:

Find a way to resolve the following usecase: 
Yaml config like this:


sockets:
  

 - name:  name1    

   port: 80
  
 - name:
  name2    

   port: 9090
      

   address: “192.168.1.1"


API expectation: Config.asList(“sockets”, SocketConfig.class) [Tomas]

[Emily-Jiang]

sockets.0.name="name1"
sockets.0.port=80
sockets.0.address=

sockets.1.name="name2"
sockets.1.port= 9090
sockets.1.address=“192.168.1.1"


@Configuration
public class SocketConfig{
 private String name;
 private int port;
 private String address;
}

[smoyer64]

It should be possible to make a YAML/JSON ConfigSource that turns the hierarchy that's possible in those formats into the classic "dotted-notation" used in Java properties files. Many JSON parsers provide this functionality out-of-the-box.

[sebadiaz]

Like Akka Typesafe config !

[struberg]

Socket[] serverSockets = config.getValue("sockets", SocketConfig[].class);

[Emily-Jiang]

In today's hangout, we come into conclusion on the requirement of the need of introducing another way to opt in property files, maybe using prefix saying javax-configxxx to opt in the tree-structure files e.g. javax-config.json or javax-config.yaml

[Emily-Jiang]

@tomas-langer @sebadiaz and @Emily-Jiang met today and agreed the following mapping strategy from tree structure to config name:
sockets.0.name="name1"
sockets.0.port=80
sockets.0.address=

sockets.1.name="name2"
sockets.1.port= 9090
sockets.1.address=“192.168.1.1"


................
We need to think about how to inject the configure property to an object, similar like:
@configuration
public class SocketConfig{
private String name;
private int port;
private String address;
}

[Emily-Jiang]

@ConfigProperty(cacheFor=3)
public interface SocketConfig{
   @ConfigProperty(name="sockets")
   String getName();
    int getPort();
    String getAddress();
}