Add support of write attributes at client side.

[sbernard31]

This means :

1. be able to handle write request attributes and store attributes
2. use this attributes to raise notification
3. show attributes in Discover response

There is an ongoing work about this (#484) : #1514

The LWM2M v1.1.1 specification about that :

• LWM2M-v1.1.1@core§5.1. Attributes
• LWM2M-v1.1.1@core§6.3.4. Write-Attributes Operation
• LWM2M-v1.1.1@core§6.4.2. Notify Operation
• Enabler Test Specification (Interoperability) for Lightweight - v1.1 (tests LightweightM2M-1.1-int-710, LightweightM2M-1.1-int-810, LightweightM2M-1.1-int-910)

It could be worth to also check LWM2M v1.2.x, just for clarification (not for new feature) :

• LWM2M-v1.2.1@core§7.3. Attributes
• LWM2M-v1.2.1@core§6.3.4. Write-Attributes Operation
• LWM2M-v1.2.1@core§6.4.2. Notify Operation
• Enabler Test Specification (Interoperability) for Lightweight - v1.2 (tests LightweightM2M-1.1-int-261, LightweightM2M-1.2-int-264, LightweightM2M-1.2-int-266, LightweightM2M-1.1-int-301, LightweightM2M-1.1-int-308,LightweightM2M-1.1-int-310,LightweightM2M-1.2-int-313,LightweightM2M-1.1-int-760,LightweightM2M-1.1-int-951, LightweightM2M-1.1-int-1203, LightweightM2M-1.1-int-1204,LightweightM2M-1.1-int-1900)

LWM2M v1.1.x also refer to IETF draft-ietf-core-dynlink-07 as [DynLink], so it could also make to look at it to clarify some ambiguities. Since draft 14, Conditional Attributes section was moved to draft-ietf-core-conditional-attributes. LWM2M v1.2.x refer to this last one draft-ietf-core-conditional-attributes-06 as [Cond_Attr]. So it could also make to look at it to clarify some ambiguities.

There is also some old discussion at OMA Developer repository which could maybe help (when we don't find answer in official specification) :

• Effect of attributes on different assignment levels OpenMobileAlliance/OMA_LwM2M_for_Developers#478
• Attribute Assignation Level inconsistency ?  OpenMobileAlliance/OMA_LwM2M_for_Developers#539

[rkimsb2]

+1

[henris42]

Hi, any news on this one? I have an urgent need to somehow handle PMAX/PMIN attribute requests in the client. The client now answers with 500 Internal Error, which is not tolerated by our server - we cannot observe anything.

I'm happy also with ANY workaround, PMAX/PMIN do not need to actually work in this application, we just need to get the server the expected response (204 I believe)

[sbernard31]

Clearly not a priority for us now.
This could need some modification at californium side, meaning this could be a not so easy task.
The only hope : an unintended contribution. So I won't bet on this at short term.

Anyway a possible workaround:
You need a custom ObjectEnabler which do what you want on WriteAttributesRequest
E.g :

public class CustomObjectEnabler extends ObjectEnabler {

    public CustomObjectEnabler(int id, ObjectModel objectModel, Map<Integer, LwM2mInstanceEnabler> instances,
            LwM2mInstanceEnablerFactory instanceFactory, ContentFormat defaultContentFormat) {
        super(id, objectModel, instances, instanceFactory, defaultContentFormat);
    }

    @Override
    public synchronized WriteAttributesResponse writeAttributes(ServerIdentity identity,
            WriteAttributesRequest request) {
        return WriteAttributesResponse.success();
    }
}

Then if you are using ObjectsInitializer you can create a custom one too :

public class CustomObjectsInitializer extends ObjectsInitializer {

    @Override
    protected ObjectEnabler createNodeEnabler(ObjectModel objectModel) {
        Map<Integer, LwM2mInstanceEnabler> instances = new HashMap<>();
        LwM2mInstanceEnabler[] newInstances = createInstances(objectModel);
        for (LwM2mInstanceEnabler instance : newInstances) {
            // set id if not already set
            if (instance.getId() == null) {
                int id = BaseInstanceEnablerFactory.generateNewInstanceId(instances.keySet());
                instance.setId(id);
            }
            instance.setModel(objectModel);
            instances.put(instance.getId(), instance);
        }
        return new CustomObjectEnabler(objectModel.id, objectModel, instances, getFactoryFor(objectModel),
                getContentFormat(objectModel.id));
    }
}

And this should be OK.
HTH.

[henris42]

Hi,

Yes I got it working with this, thanks!

[dellzhui]

Clearly not a priority for us now. This could need some modification at californium side, meaning this could be a not so easy task. The only hope : an unintended contribution. So I won't bet on this at short term.

Anyway a possible workaround: You need a custom ObjectEnabler which do what you want on WriteAttributesRequest E.g :

public class CustomObjectEnabler extends ObjectEnabler {

    public CustomObjectEnabler(int id, ObjectModel objectModel, Map<Integer, LwM2mInstanceEnabler> instances,
            LwM2mInstanceEnablerFactory instanceFactory, ContentFormat defaultContentFormat) {
        super(id, objectModel, instances, instanceFactory, defaultContentFormat);
    }

    @Override
    public synchronized WriteAttributesResponse writeAttributes(ServerIdentity identity,
            WriteAttributesRequest request) {
        return WriteAttributesResponse.success();
    }
}

Then if you are using ObjectsInitializer you can create a custom one too :

public class CustomObjectsInitializer extends ObjectsInitializer {

    @Override
    protected ObjectEnabler createNodeEnabler(ObjectModel objectModel) {
        Map<Integer, LwM2mInstanceEnabler> instances = new HashMap<>();
        LwM2mInstanceEnabler[] newInstances = createInstances(objectModel);
        for (LwM2mInstanceEnabler instance : newInstances) {
            // set id if not already set
            if (instance.getId() == null) {
                int id = BaseInstanceEnablerFactory.generateNewInstanceId(instances.keySet());
                instance.setId(id);
            }
            instance.setModel(objectModel);
            instances.put(instance.getId(), instance);
        }
        return new CustomObjectEnabler(objectModel.id, objectModel, instances, getFactoryFor(objectModel),
                getContentFormat(objectModel.id));
    }
}

And this should be OK. HTH.

Hi sbernard31,
Your sample code solves the problem I had perfectly, it's 2022 now, why don't we put it in ObjectsInitializer and implement it