[JENA-505] NPE in the OWL class

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Done
• Affects Version/s: Jena 2.10.1
• Fix Version/s: Jena 2.11.0
• Component/s: Jena
• Assignee: Andy Seaborne
• Reporter: Piotr Hołubowicz
• Created: 09/Aug/13 11:36
• Updated: 01/Feb/15 19:12
• Resolved: 01/Feb/15 19:12

Description

The error happens when you try to load a file using the file manager in Jena 2.10.1, for example

model = FileManager.get().loadModel("http://example.org","http://example.org","RDF/XML");

The reason is incorrect initialization of variables in the OWL class. In the following code:

    public class OWL {
        private static Model m_model = ModelFactory.createDefaultModel();
        
        public static final String NS = "http://www.w3.org/2002/07/owl#";
        
        public static String getURI() {return NS;}
    
    ...    
        public static final Property sameAs = m_model.createProperty( "http://www.w3.org/2002/07/owl#sameAs" );
    ...

a call to OWL.sameAs will result in a NPE because m_model is null. I guess that if you start with OWL.getURI(), then m_model will be evaluated first and there will be no error, which is why this never occurred before.

I think that a solution would be to make m_model final as well.