Hi, Richard
I have solved the problem! Everything is working well now.
Thank you so much for your help! I am so happy!!!!(^-^)
Ly ,

--- In jena-dev@yahoogroups.com, Richard Cyganiak <richard@c...> wrote:
>
> Hi Ly,
>
> On 14 Jan 2006, at 10:14, bichly81 wrote:
>
> > Hi,
> > I am trying to save model to MySQL and access it. First, I create an
> > model "m" in RDF, make a connection to mySQL and create model
> > "model".Then set model=m and print it out to check.
>
> Variables in Java are references to objects. The effect of "=" is
> that after the assignment, the variable on the left side refers to
> the result of the right side. Assignment with "=" can never do
> anything "interesting" in Java, like inserting something into a
> database. Assignment only makes a variable point to another object.
>
> So before "model = m", you have this:
>
> m refers to your in-memory model object.
> model refers to your database model object.
>
> After "model = m":
>
> m refers to your in-memory model object.
> model also refers to the in-memory model object.
> No variable refers to the database model object any more! It'll get
> garbage collected. That's how Java works.
>
> So, when you print out model, you get the expected result, but you're
> actually printing the in-memory model, and not the database model!
>
> Apologies if this is confusing!
>
> I think what you tried to do is to *add* all the statements from the
> in-memory model to the database model. You can do it like this:
>
> model.add(m);
>
> After this, model of course still refers to the database model, but
> the "add" method copies all statements from the argument into the
> database model.
>
> (No, "model = model + m" won't work ;-)
>
> Hope that helps,
> Richard
>
>
> >
> > Class.forName(DRIVER);
> > IDBConnection conn = new DBConnection(M_DB_URL, M_DB_USER,
> > M_DB_PASSWD, M_DB);
> > ModelMaker maker = ModelFactory.createModelRDBMaker(conn);
> > model = maker.createModel(modelName);
> > model=m;
> > model.write( System.out ,"RDF/XML-ABBREV");
> > conn.close();
> >
> >
> > At this point,everything seems going well.The output is right with a
> > long RDF file.
> >
> > But then when I make a new connection and access the the databases
> > to access the model with
> >
> > model = maker.openModel(modelName);
> > model.write( System.out ,"RDF/XML-ABBREV");
> >
> > I got the result with just
> >
> > <rdf:RDF
> > xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" >
> > </rdf:RDF>
> >
> > What happened to MySQL database? What should I do to solve te
> > problem?
> >
> > Thank you,
> > Ly,
> >
> >
> >
> >
> >
> >
> >
> >
> > Yahoo! Groups Links
> >
> >
> >
> >
> >
> >
> >
>