Yes you are right sir, it is a project based assignment but stuck in the
first portion/part of creating individuals based on user entered string.
I initialized the OntModel in the button handler as:
jButton1ActionPerformed(java.awt.event.ActionEvent evt) {
OntModel model=ModelFactory.createOntologyModel();
String str=jTextField2.getText();
read1(str, model);
null pointer exception disappear and it gives error of :
line 1 co*lumn 1): Content is not allowed in prolog.*
I think this is due to some white spaces but it usually happens when there
are some xml tags. What type of white space will be there in a jena code?
On Thu, Jul 14, 2016 at 11:24 PM, Lorenz B. <
buehm...@informatik.uni-leipzig.de> wrote:
> OntModel is the in-memory knowledge base.That's where you create the
> individual. By the way, some of your class mates asked similar things on
> Stackoverflow, so it looks like you're doing some assignments.
> I also don't see the problem. A user enters a String and you use this to
> create the individual. That are more or less Java basics.
>
> > I am sorry but I thought if Ontclass can be passed as null, so shall be
> > OntModel. My sole purpose is to pass the string entered by user to the
> > read() which can be used create individuals.
> >
> > On Thu, Jul 14, 2016 at 5:03 AM, Lorenz B. <
> > buehm...@informatik.uni-leipzig.de> wrote:
> >
> >> 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
> >>
> >>
> --
> Lorenz Bühmann
> AKSW group, University of Leipzig
> Group: http://aksw.org - semantic web research center
>
>
