In which the second argument is the class and not the model as in your code. It looks like you did mostly copy and paste without understanding the code.
In your case the model is ALWAYS null, do you understand that? > I have read it here: > http://tutorial-academy.com/category/java/ > > He used null argument in the main() method: > > public static void main(String[] args) > { > // create OntModel > OntModel model = ModelFactory.createOntologyModel(); > // read camera ontology > readOntology( "./ontology/camera.owl", model ); > // start traverse > traverseStart( model, null ); > } > > On Thu, Jul 14, 2016 at 4:09 AM, Lorenz B. < > buehm...@informatik.uni-leipzig.de> wrote: > >> I don't get it. Where did you saw this in the Jena tutorial? >> >> And do you understand that when you call in your main() >> >> read(str, null); >> >> that the second argument is always null, thus, the code will never go >> into the if-clause? >> >>> The read() method is given below: I used null reference after reading >> this >>> tutorial of Jena which used it in main(). >>> *Since I have to create individual of name entered in text field and then >>> button clicked, either I need OntClass in button handler or the string of >>> text field in the read() method.* >>> >>> private static void read(String str, OntModel model) >>> { >>> //OntModel model = ModelFactory.createOntologyModel(); >>> >>> String ns="http://www.semanticweb.org/untitled-ontology-004/";; >>> >>> if (model!= null ) { >>> >>> OntClass user1 = model.getOntClass(ns + "User"); >>> Individual janeSmith = user1.createIndividual(ns + str); >>> >>> >>> try { >>> String file="F://updated.owl"; >>> >>> >>> FileWriter out=new FileWriter(file); >>> >>> model.write( out, "RDF/XML-ABBREV" ); >>> } catch (IOException ex) { >>> Logger.getLogger(NewJFrame.class.getName()).log(Level.SEVERE, >>> null, ex); >>> } >>> } >>> >>> On Thu, Jul 14, 2016 at 1:38 AM, Lorenz B. < >>> buehm...@informatik.uni-leipzig.de> wrote: >>> >>>> Andy already told you correctly that you call >>>> >>>> read(str, null) thus the second argument is null. >>>> >>>> Moreover, you did not show the read() method but only readOntology(), >>>> thus, nobody knows what's going inside the read() method. But obviously, >>>> some object is null and you call a method on that. I suggest to use a >>>> Java debugger. >>>> >>>>> *As I also mentioned in the code: model.write(), it writes the rdf to >>>>> console and load the GUI also.* >>>>> *But when I enter text and press button ,it gives exception error:* >>>>> >>>>> Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException >>>>> at javaapplication4.NewJFrame.read(NewJFrame.java:53) >>>>> at >> javaapplication4.NewJFrame.jButton3ActionPerformed(NewJFrame.java:287) >>>>> at javaapplication4.NewJFrame.access$100(NewJFrame.java:27) >>>>> at javaapplication4.NewJFrame$2.actionPerformed(NewJFrame.java:135) >>>>> >>>>> On Wed, Jul 13, 2016 at 2:27 PM, Andy Seaborne <a...@apache.org> >> wrote: >>>>>> This looks rather similar to ; >>>>>> >>>>>> >> http://stackoverflow.com/questions/38351713/creating-individual-in-jena >>>>>> I suggest local collaboration. >>>>>> >>>>>> >>>>>> On 13/07/16 16:37, kumar rohit wrote: >>>>>> >>>>>>> Hi >>>>>>> I have the following code in which I want to create an >>>> instance/individual >>>>>>> of the class Student. The student name is entered in a text box (in a >>>>>>> button even handler). But it gives exception. >>>>>>> >>>>>>> _________________________________________ >>>>>>> >>>>>>> public class NewJFrame extends javax.swing.JFrame { >>>>>>> >>>>>>> public static void readOntology( String file, OntModel model ) >>>>>>> { >>>>>>> >>>>>>> InputStream in = null; >>>>>>> try >>>>>>> { >>>>>>> in = new FileInputStream( file ); >>>>>>> model.read(in, "RDF/XML"); >>>>>>> in.close(); >>>>>>> } catch (IOException e) >>>>>>> { >>>>>>> e.printStackTrace(); >>>>>>> } >>>>>>> >>>>>>> My main() is the following. >>>>>>> >>>>>>> ________________________________ >>>>>>> >>>>>>> public static void main(String args[]) { >>>>>>> >>>>>>> >>>>>>> >>>>>>> OntModel model = ModelFactory.createOntologyModel(); >>>>>>> String file="D://std.owl"; >>>>>>> readOntology(file , model ); >>>>>>> _______________________________________ >>>>>>> >>>>>>> Button handler to get student name from text box is: >>>>>>> >>>>>>> private void jButton2ActionPerformed(java.awt.event.ActionEvent >> evt) >>>> { >>>>>>> >>>>>>> >>>>>>> String str=jTextField1.getText(); >>>>>>> >>>>>>> read(str, null); >>>>>>> } >>>>>>> _____________________________________ >>>>>>> >>>>>>> WARN [main] (RDFDefaultErrorHandler.java:36) - unknown-source: {W136} >>>>>>> Relative URIs are not permitted in RDF: specifically <RDF/XML> >>>>>>> >>>>>>> >>>>>>> >>>>>>> Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException >>>>>>> at javaapplication4.NewJFrame.read(NewJFrame.java:50) >>>>>>> at >>>> javaapplication4.NewJFrame.jButton2ActionPerformed(NewJFrame.java:266) >>>>>>> at javaapplication4.NewJFrame.access$000(NewJFrame.java:27) >>>>>>> at javaapplication4.NewJFrame$1.actionPerformed(NewJFrame.java:103) >>>>>>> at >>>>>>> >>>> javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2022) >>>>>>> at >>>>>>> >>>>>>> >> javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2348) >>>>>>> at >>>>>>> >>>>>>> >> javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402) >>>>>>> at >>>> javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259) >>>> -- >>>> Lorenz Bühmann >>>> AKSW group, University of Leipzig >>>> Group: http://aksw.org - semantic web research center >>>> >>>> >> -- >> Lorenz Bühmann >> AKSW group, University of Leipzig >> Group: http://aksw.org - semantic web research center >> >> -- Lorenz Bühmann AKSW group, University of Leipzig Group: http://aksw.org - semantic web research center
