peppol-lookup: DummyLookupClient implementation

[dladlk]

LookupClient class in peppol-lookup is quite flexible - it is possible to define in configuration custom implementations of each its part:

• locator to build URL hostname for SMP resource
• metadata provider to fill URL with path
• fetcher to download XML data
• reader to parse it

But it does not provide a way to overwrite the whole implementation of LookupClient, e.g. for testing purposes.

All mentioned parts are configurable via mode.default.lookup.PART.class - except LookupClient implementation, see https://github.com/OxalisCommunity/vefa-peppol/blob/56ab2e5a128081f733794ae69493b480c68bc34b/peppol-lookup/src/main/resources/reference.conf

In this discussion it is proposed to expand configuration with mode.default.lookup.impl.class = network.oxalis.vefa.peppol.lookup.LookupClient and make LookupClient instantiation dynamic in LookupClientBuilder (see last 4 lines below):

    public LookupClient build() throws PeppolLoadingException {
        if (metadataLocator == null)
            locator(mode.initiate("lookup.locator.class", MetadataLocator.class));
        if (metadataProvider == null)
            provider(mode.initiate("lookup.provider.class", MetadataProvider.class));
        if (metadataFetcher == null)
            fetcher(mode.initiate("lookup.fetcher.class", MetadataFetcher.class));
        if (metadataReader == null)
            reader(mode.initiate("lookup.reader.class", MetadataReader.class));

        // Replace fixed implementation with dynamic        
        // return new LookupClient(this);
        Map<String, Object> map = new HashMap<String, Object>();
        map.put(LookupClientBuilder.class.getName(), this);
        return mode.initiate("lookup.impl.class", null, map); 
    }

and provide an example of DummyLookupClient implementation and configuration, which can be overwritten via reference.conf at application class path e.g. like this:

mode.TEST.lookup.impl.class = network.oxalis.vefa.peppol.lookup.dummy.DummyLookupClient

mode.TEST.lookup.impl.dummy = {
	uri: "http://localhost:8080/as4"
	certificate: "MIIGkTCCBMWgAwIBA...+jUH1N7v7JJdaA="
	transport: "peppol-transport-as4-v2_0"
	process: "urn:fdc:peppol.eu:2017:poacc:billing:01:1.0"
	doctype: "urn:oasis:names:specification:ubl:schema:xsd:Invoice-2::Invoice##urn:cen.eu:en16931:2017#compliant#urn:fdc:peppol.eu:2017:poacc:billing:3.0::2.1"
}

Theoretically, it can be also used for a "standalone" version, to omit multiple parameters in command line, but definition of the "static" lookup result via reference.conf.

[dladlk]

The suggestion is implemented and submitted as a pull request #50

Potential improvements:

• extract interface for LookupClient (now DummyLookupClient just extends LookupClient)
• change the configuration key in reference.conf - now it is lookup.impl.class (to be similar to e.g. lookup.fetcher.class) and lookup.dummy.urletc - can be something else if word dummy is too broad.