add Read-Composite request support

[sbernard31]

I'm currently thinking about Read-Composite API.

See :

• core§6.3.8-Read-Composite-Operation
• transport§6.4.4-Device-Management-and-Service-Enablement-Interface

I guess the request should looks like this :

new ReadCompositeRequest(requestContentFormat,responseContentFormat, String path ...);
// or maybe but currently LwM2mPath is pretty much not exposed API
new ReadCompositeRequest(requestContentFormat,responseContentFormat, LwM2mPath path ...);

For the response, this is less easy, I currently have no idea how it should looks like, especially the payload (content) part.

public class ReadCompositeResponse {

    ResponseCode getCode();
    ???? getContent();
}

I suppose we could imagine :

• Collection<LwM2mNode> getContent() pretty straightforward but not sure this is so easy to use API :/
• Map<String,LwM2mNode> where we match a response for each request path but this could be an issue for "/" use case where there is not 1 LwM2mNode but several.
• NavigableMap<LwM2mPath,Lwm2mNode> which should allow a better way to navigate in received data but API will not be so straightforward too
• or maybe we need a new dedicated structure based on NaviableMap which could allow to extract data for a given path ?

[sbernard31]

(@yemkay, @madhushreegc you may be interested by this)

[sbernard31]

I'm currently exploring the Map<String,LwM2mNode> way because it seems to be the less impacting way.
(for "/" case I will maybe need a LwM2mRootNode)

[madhushreegc]

Map<String,LwM2mNode> , key is LWM2M path?

[sbernard31]

Yes that's the idea.

[eliasweingaertner]

I definitely like it. I also think that Map<String,LwM2mNode> with the key being the path is a simple and straightforward solution. It plays in nicely with all kinds of things like JSON Serialization, Logging, etc.

[sbernard31]

There are some news in #958 (comment).
In this version I finally use a List<LwM2mNode> getContent() 😅 ... but this is just because that was the more straightforward way for my first try. If Map is really more wanted I can implement the Map way.

[sbernard31]

The API currently looks like this : #958 (comment)
I'm still not sure this the the right way, I have this (#981) in mind but not the priority for now.

The missing part is Read-Composite on "/" : #989.

I think we can close this issue.