error in addproperty and addliteral function

Question

I am trying to store my emails in rdf models into apche tdb. Here's my code :

/*Program to download the mails from mail servers and then to store
  them in tdb store using rdf model*/
//import all the classes needed  




import java.io.*;
import java.util.*;
import javax.mail.*;
import javax.mail.Flags.Flag;
import javax.mail.internet.*;
import com.sun.mail.imap.IMAPFolder;
import com.sun.mail.imap.IMAPMessage;
import static com.hp.hpl.jena.query.ReadWrite.READ ;
import static com.hp.hpl.jena.query.ReadWrite.WRITE ;
import com.hp.hpl.jena.query.ReadWrite ;
import com.hp.hpl.jena.query.Dataset ;
import com.hp.hpl.jena.query.Query ;
import com.hp.hpl.jena.query.QueryExecution ;
import com.hp.hpl.jena.query.QueryExecutionFactory ;
import com.hp.hpl.jena.query.QueryFactory ;
import com.hp.hpl.jena.query.QuerySolution ;
import com.hp.hpl.jena.query.ResultSet ;
import com.hp.hpl.jena.tdb.TDBFactory ;
import email.*; // import this to add properties as entities of email
import com.hp.hpl.jena.rdf.model.Model;
import com.hp.hpl.jena.rdf.model.*;
import com.hp.hpl.jena.vocabulary.*;


public class test2 {


public static void main(String[] args) throws MessagingException, IOException {
    IMAPFolder folder = null;
    Store store = null;
    String subjec = null;
    Flag flag = null;
    //String too;
    //Directory where the tdb files will be stored
     String directory = "MYDATABASES/DATA2" ;
     //create the dataset for the tdb store
    Dataset ds = TDBFactory.createDataset(directory) ;
    //create default rdf model
    Model model = ds.getDefaultModel() ;
    //write to the tdb dataset
    ds.begin(ReadWrite.WRITE);
    try 
    { //connecting to the server to download the emails
      Properties props = System.getProperties();
      props.setProperty("mail.store.protocol", "imaps");

      Session session = Session.getDefaultInstance(props, null);

      store = session.getStore("imaps");
      store.connect("imap.gmail.com","[email protected]", "ferry@786");

      //folder = (IMAPFolder) store.getFolder("[Gmail]/Spam"); // This doesn't work for enter code here`other email account
      //to select the paticular types of mails
      folder = (IMAPFolder) store.getFolder("inbox");// This works for both email account


      if(!folder.isOpen())
      folder.open(Folder.READ_WRITE);
      Message[] messages = folder.getMessages();
      System.out.println("No of Messages : " + folder.getMessageCount());
      System.out.println("No of Unread Messages : " + folder.getUnreadMessageCount());
      System.out.println(messages.length);
      //Displaying the info. of the messages
       for (int i=messages.length-1; i > messages.length-10;i--) 
      {

        System.out.println("*****************************************************************************");
        System.out.println("MESSAGE " + (i + 1) + ":");
        MimeMessage msg = (MimeMessage) messages[i];
        //creating rdf model of the message
        //too=toString(msg.getAllRecipients()[0]);
         Resource mail= model.createResource(msg.getMessageID())
        .addProperty(EMAILRDF.SUBJECT, msg.getSubject())  
        .addProperty(EMAILRDF.TO,msg.getAllRecipients()[0])
        .addLiteral(EMAILRDF.FROM,msg.getFrom()[0])
        .addLiteral(EMAILRDF.ENCODING,msg.getEncoding())
        .addLiteral(EMAILRDF.CONTENT,msg.getContent())
        .addLiteral(EMAILRDF.DATE,msg.getReceivedDate())
        .addLiteral(EMAILRDF.CONTENT_TYPE,msg.getContentType());

    // list the statements in the graph
    StmtIterator iter = model.listStatements();

    // print out the predicate, subject and object of each statement
    while (iter.hasNext()) {
        Statement stmt      = iter.nextStatement();         // get next statement
        Resource  subject   = stmt.getSubject();   // get the subject
        Property  predicate = stmt.getPredicate(); // get the predicate
        RDFNode   object    = stmt.getObject();    // get the object

        System.out.print(subject.toString());
        System.out.print(" "+ predicate.toString() + " ");
        if (object instanceof Resource) {
            System.out.print(object.toString());
        } else {
            // object is a literal
            System.out.print(" \"" + object.toString() + "\"");
        }
        System.out.println(" .");
    }
        //System.out.println(msg.getMessageNumber());
        //Object String;
        //System.out.println(folder.getUID(msg)

        //subject = msg.getSubject();

        //System.out.println("Subject: " + subject);
        //System.out.println("From: " + msg.getFrom()[0]);
        //System.out.println("To: "+msg.getAllRecipients()[0]);
        //System.out.println("Date: "+msg.getReceivedDate());
        //System.out.println("Size: "+msg.getSize());
        //System.out.println("Id: "+msg.getMessageID());
        //System.out.println(msg.getFlags());
        //System.out.println("Body: \n"+ msg.getContent());
        //System.out.println(msg.getContentType());

      }
    }
    finally 
    {  //closing the connection
      if (folder != null && folder.isOpen()) { folder.close(true); }
      if (store != null) { store.close(); }
    }


 //closing the dataset
ds.commit();
ds.end();
}
}

But this gives error in the addLteral() method .I tried using AddProperty() but that also gives error.

error: WARN [main] (LiteralLabelImpl.java:141) - inventing a datatype for class com.sun.mail.imap.protocol.IMAPAddress
Exception in thread "main" java.lang.NullPointerException
    at com.hp.hpl.jena.datatypes.TypeMapper.getTypeByValue(TypeMapper.java:156)
    at com.hp.hpl.jena.graph.impl.LiteralLabelImpl.<init>(LiteralLabelImpl.java:131)
    at com.hp.hpl.jena.graph.impl.LiteralLabelFactory.create(LiteralLabelFactory.java:77)
    at com.hp.hpl.jena.rdf.model.impl.ModelCom.createTypedLiteral(ModelCom.java:781)
    at com.hp.hpl.jena.rdf.model.impl.ResourceImpl.addLiteral(ResourceImpl.java:263)
    at test2.main(test2.java:80)

I think that it may possibly due to the datatype of class I am entering in the addproperty() or addLiteral() function .
Any Idea???

Answer 1

This is probably answered sufficiently by the JavaDoc. Resource defines a number of addLiteral methods, each of which takes a property, and a second argument of type boolean, char, double, float, Literal, long, or Object. Based on the warning, "WARN [main] (LiteralLabelImpl.java:141) - inventing a datatype for

class com.sun.mail.imap.protocol.IMAPAddress," it sounds like you're using the addLiteral(Property,Object) method.

When you do that, as the JavaDoc says, you're trying to

Add the property p with the typed-literal value o to this resource, ie add (this, p, typed(o)) to this's model. … The typed literal is equal to one constructed by using this.getModel().createTypedLiteral(o).

You can see from the stacktrace that createTypedLiteral is being called, and it's not surprising that there's no datatype defined for com.sun.mail.imap.protocol.IMAPAddress. Whichever call to addLiteral has an IMAPAddress as the second argument you'll need to replace to a call with a second argument that can be converted to a typed literal. The easiest way to do that will probably be to use its toString() method.