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From "Aaron Coburn (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (COMMONSRDF-73) Jena module has Simple dependency, SPI will never work
Date Mon, 27 Nov 2017 19:11:00 GMT

    [ https://issues.apache.org/jira/browse/COMMONSRDF-73?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16267279#comment-16267279
] 

Aaron Coburn commented on COMMONSRDF-73:
----------------------------------------

Hi [~zakmck], I have some similar code [here|https://github.com/trellis-ldp/trellis-api/blob/master/src/main/java/org/trellisldp/api/RDFUtils.java#L37],
which is an API that gets used by an LDP server. It, too, is independent of RDF implementations.
As you have pointed out, when using commons-rdf-jena, the commons-rdf-simple jar *does* end
up on the classpath, but I still will always get a JenaRDF object from `getInstance()`, since
elsewhere in the code a JenaRDF object is instantiated.

> Jena module has Simple dependency, SPI will never work
> ------------------------------------------------------
>
>                 Key: COMMONSRDF-73
>                 URL: https://issues.apache.org/jira/browse/COMMONSRDF-73
>             Project: Apache Commons RDF
>          Issue Type: Bug
>          Components: jena
>    Affects Versions: 0.3.0
>            Reporter: Marco Brandizi
>
> I'm trying to setup the RDF object one should use with Commons-RDF in a transparent way,
using the SPI mechanism, ServiceLoader and META-INF/org.apache.commons.rdf.api.RDF. 
> This is the code I'm using:
> {code:java}
> private synchronized static RDF getDefaultRdf () 
> {
> 	if ( defaultRdf != null ) return defaultRdf;
> 	
> 	ServiceLoader<RDF> loader = ServiceLoader.load ( RDF.class );
> 	Iterator<RDF> itr = loader.iterator();
> 	
> 	if ( !itr.hasNext () ) throw new RdfException (
> 		"No implementation found for Commons RDF, please, review your dependencies/classpath"
> 	);
> 	defaultRdf = itr.next();
> 	if ( itr.hasNext () ) log.warn ( 
> 		"More than one RDF instance available for Commons RDF, taking the first one ({})",

> 		itr.next ().getClass ().getName () 
> 	);	
> 	
> 	return defaultRdf;
> }
> {code}
> I've done a first test with the Jena module (commons-rdf-jena). SPI is broken by the
fact this module also declares commons-rdf-simple as one of its dependencies. At least in
Maven, the META-INF in commons-rdf-simple is the first that is met in the classpath and the
simple implementation is the one that is picked by the code above, as reported by the warning.
I expect the Jena implementation to be pulled up when I link the jena module as the only dependency.
> Such dependency should be removed, and not just because of this problem (different commons
implementations should be independent of each other). I've given a look at the source files
and it seem the rdf-simple module is only used for testing purposes (but physically is in
the main code folders).



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