Some Idea to try to improve API to create CaliforniumServerEndpointsProvider

[sbernard31]

After discussion at #1383, I tried to think about how to improve API to create CaliforniumServerEndpointsProvider.
Here some ideas, where Coaps is used as example but could be generalized to all kind of protocol based on Californium :

---

A)

Being able to customize dtlsConfig on CoapsProtocolProvider. (See #1382 for more details)

e.g. proposed API :

LeshanServerBuilder serverBuilder = new LeshanServerBuilder();

CaliforniumServerEndpointsProvider.Builder endpointsBuilder = new CaliforniumServerEndpointsProvider.Builder(
        // add CoAP protocol Provider
        new CoapServerProtocolProvider(),

        // add CoAPS protocol Provider.
        new CoapsServerProtocolProvider(dtlsConfigBuilder -> {
            dtlsConfigBuilder.setSessionStore(new CustomSessionStore());
        }));

serverBuilder.setEndpointsProvider(endpointsBuilder.build());

---

B)

Currently the way to customize a Californium configuration looks like this :

LeshanServerBuilder serverBuilder = new LeshanServerBuilder();

CaliforniumServerEndpointsProvider.Builder endpointsBuilder = new CaliforniumServerEndpointsProvider.Builder(
        new CoapServerProtocolProvider(), new CoapsServerProtocolProvider());

// Change Californium configuration :
Configuration californiumConfig = endpointsBuilder.createDefaultConfiguration();
californiumConfig.set(DtlsConfig.DTLS_RECOMMENDED_CIPHER_SUITES_ONLY, true);
californiumConfig.set(CoapConfig.ACK_TIMEOUT  , 1, TimeUnit.SECONDS);
endpointsBuilder.setConfiguration(californiumConfig);

serverBuilder.setEndpointsProvider(endpointsBuilder.build());

Maybe it would be better to propose this way instead (or in addition) :

LeshanServerBuilder serverBuilder = new LeshanServerBuilder();

CaliforniumServerEndpointsProvider.Builder endpointsBuilder = new CaliforniumServerEndpointsProvider.Builder(
        new CoapServerProtocolProvider(), new CoapsServerProtocolProvider());

// Change Californium configuration : 
// This configuration will be used for whole CoAP Server and so all endpoints.
endpointsBuilder.setConfiguration(c -> {
    c.set(DtlsConfig.DTLS_RECOMMENDED_CIPHER_SUITES_ONLY, true);
    c.set(CoapConfig.ACK_TIMEOUT , 1, TimeUnit.SECONDS);
});

serverBuilder.setEndpointsProvider(endpointsBuilder.build());

---

C)

The "normal way" to create californium based endpoint is :

LeshanServerBuilder serverBuilder = new LeshanServerBuilder();

CaliforniumServerEndpointsProvider.Builder endpointsBuilder = new CaliforniumServerEndpointsProvider.Builder(
        new CoapServerProtocolProvider(), new CoapsServerProtocolProvider());

endpointsBuilder.addEndpoint(new InetSocketAddress(5784), Protocol.COAP);
endpointsBuilder.addEndpoint("coaps://localhost:5684");

serverBuilder.setEndpointsProvider(endpointsBuilder.build());

If default endpoint created by ProtocolProvider is not enough, you can :

endpointsBuilder.addEndpoint(new CoapsServerEndpointFactory(coapUri));

But currently there is no easy way to configure the CoapsServerEndpointFactory without creating a new class which inherits it.

An alternative could be to create a Builder which could like like :

endpointsBuilder.addEndpoint(new CoapsServerEndpointFactoryBuilder() //
        .uri(5784) //
        .loggingTagPrefix("Custom Coaps") //
        .dtlsConfig(c -> c.setSessionStore(new CustomSessionStore())) //
        .endpointConfig(c -> c.setTokenGenerator(new CustomTokenGenerator())) //
        // if used, endpoint will used a specific config instead of the CoAP server one. (see point B. 👆 )
        .configuration(c -> c.set(CoapConfig.ACK_TIMEOUT  , 1, TimeUnit.SECONDS)) //
        .build());

[cyril2maq]

The CoapsServerEndpointFactoryBuilder (C) proposal seems the most readable API to me.

It allows to set dedicated options without having to read, understand and override the whole CoapsServerEndpointFactory class.

[sbernard31]

Reading your answer, I feel that maybe I was not clear enough.

So just to be sure, proposition A), B) and C) are not exclusive and doesn't target same goal.

About C), the full snippet of code would be :

LeshanServerBuilder serverBuilder = new LeshanServerBuilder();

CaliforniumServerEndpointsProvider.Builder endpointsBuilder = new CaliforniumServerEndpointsProvider.Builder(
        new CoapServerProtocolProvider(), new CoapsServerProtocolProvider());

// to add default endpoint for COAP and COAPS
endpointsBuilder.addEndpoint(Protocol.COAP);
endpointsBuilder.addEndpoint(Protocol.COAPS);

// to add another COAPS endpoint which custom config. 
endpointsBuilder.addEndpoint(new CoapsServerEndpointFactoryBuilder() //
        .uri(5784) //
        .loggingTagPrefix("Custom Coaps") //
        .dtlsConfig(c -> c.setSessionStore(new CustomSessionStore())) //
        .endpointConfig(c -> c.setTokenGenerator(new CustomTokenGenerator())) //
        .configuration(c -> c.set(CoapConfig.ACK_TIMEOUT  , 1, TimeUnit.SECONDS)) //
        .build());

// so the endpoints provider will provide 3 endpoints, 1 for coap and 2 for coaps.
serverBuilder.setEndpointsProvider(endpointsBuilder.build());

[sbernard31]

This ideas are implemented at : #1407

[sbernard31]

This is now integrated in master (See PR #1407)