Corba application using database

Question

Hy,

i have on the server using ORB a class that uses connection with a derby database, but it seems not to connect to database. I query using a client the server with ORB for a string. The result of the string should be another string returned from database.

Bellow is my IDL interface:

    module ZodieApp{
   interface Zodie{
      string zodie(in string a);
   };
};

The class used to connect to database is called ZodieDatabase and it uses Derby.

The server app is:

    import ZodieApp.*;
import org.omg.CosNaming.NameComponent;
import org.omg.CosNaming.NamingContextExtHelper;
import org.omg.CosNaming.NamingContextExt;
import org.omg.CORBA.ORB;
import org.omg.PortableServer.POA;
import org.omg.PortableServer.POAHelper;

public class ZodieServer {
  public static void main(String args[]) {
    try{

      ORB orb = ORB.init(args,null);


      POA rootPOA=POAHelper.narrow(orb.resolve_initial_references("RootPOA"));
      rootPOA.the_POAManager().activate();


      ZodieImpl zodieImpl = new ZodieImpl(orb);


      org.omg.CORBA.Object ref=rootPOA.servant_to_reference(zodieImpl);
      Zodie href = ZodieHelper.narrow(ref);


      org.omg.CORBA.Object objRef =
          orb.resolve_initial_references("NameService");
      NamingContextExt ncRef=NamingContextExtHelper.narrow(objRef);


      String name = "ZodieService";
      NameComponent path[] = ncRef.to_name(name);
      ncRef.rebind(path,href);

      System.out.println("ZodieServer ready and waiting ...");


      orb.run();
    } 
    catch (Exception e) {
      System.err.println("ERROR: " + e.getMessage());
    }
    System.out.println("ZodieServer Exiting ...");
  }
}

And the implementation class (the servant):

 import ZodieApp.*;
import org.omg.CORBA.ORB;

public class ZodieImpl extends ZodiePOA {
  private ORB orb;

  public ZodieImpl(ORB orb) {
    this.orb = orb; 
  }

  public String zodie(String a){
   String zodieC = ZodieDatabase.getZodie(a);
   return zodieC;
  }
}

I have created the package used in Corba app:

      Zodie.class
  Zodie.java
  ZodieHelper.class
  ZodieHelper.java
  ZodieHolder.class
  ZodieHolder.java
  ZodieOperations.class
  ZodieOperations.java
  ZodiePOA.class
  ZodiePOA.java
  _ZodieStub.class
  _ZodieStub.java

But on the client side I get null pointer exception.

Caused by: java.lang.NullPointerException
    at ZodieDatabase.getZodie(ZodieDatabase.java:66)
    at ZodieImpl.zodie(ZodieImpl.java:12)
    at ZodieApp.ZodiePOA._invoke(ZodiePOA.java:38)
    at com.sun.corba.se.impl.protocol.CorbaServerRequestDispatcherImpl.dispatchToServant(Unknown Source)
    ... 10 more

That's on the methods, that bring up the string from database.

The ZodieDatabase source code:

import ZodieApp.*;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class ZodieDatabase{  
      private String a="";
      private String zodie="aloha";
      static Statement instructiune=null;
      static Connection con=null;
      static String jdbcDriver="org.apache.derby.jdbc.ClientDriver";
      static String URLBazaDate="jdbc:derby://localhost:1527/AN_CHINEZESC";

public static void main(String[] args){
          System.out.println("Zodia:"+getZodie("1931-01-01"));
      }



        public static String getZ(String an) {
            return "Some value here";
        }

      public static String getZodie(String an){

          String zodie=null;

          try{


          Class.forName(jdbcDriver).newInstance();
          con=DriverManager.getConnection(URLBazaDate);
          instructiune=con.createStatement();
          try{
              String sql = "select an from inceput where date(an||\'-\'||luna||\'-\'||zi)="+
                      "(select max(date(an||\'-\'||luna||\'-\'||zi)) from inceput t where date(an||\'-\'||luna||\'-\'||zi) <= date(\'"
                      +an+"\'))";
              ResultSet rs=instructiune.executeQuery(sql);
              while(rs.next()){
                    //out.print(rs.getString("an"));
                 an = rs.getString("an");
                  zodie = ZodiacChinezesc.gasesteZodia(an);

                  }
          }
          catch(SQLException ex){

          }


        }
        catch(ClassNotFoundException ex){
          System.out.println("Driver inexistent JDBC: "+jdbcDriver);
        }
        catch(SQLException ex){
          System.out.println("Baza de date inexistenta "+URLBazaDate);
        }
        catch(Exception ex){
          System.out.println("Eroare : "+ex.getMessage());
        }    

          finally {
              try {
                con.close();
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
          }



      return zodie;


    }




}

Please help,

Sincerely,

A null pointer exception comes with a stacktrace, and the stacktrace comes with the class and the source file line number at which the null pointer exception occurred (unless you compiled without that information). That's the first thing to look at, and without it, many here won't attempt to answer your question. — arcy
I have looked and my issue is with jdbc driver. How I insert a reference to it? — SocketM
The exception clearly indicates that there is a problem at (ZodieDatabase.java:66) - you posted all code EXCEPT the one that is important (whats happening at (ZodieDatabase.java:66) ?) — Gyro Gearless
It enters the finnaly block and closes the connection: finally { try { con.close(); The "con.close();" it's on line 66 — SocketM
So the only way con.close() is going to throw a null pointer exception is if con is null; do you have sysout output indicating that an error was thrown while trying to connect? It should have further information about what the error is... — arcy

SocketM SocketM · Accepted Answer · 2015-01-28T13:04:09

I solved the above issue. I moved the database class into implementation class, after that I compiled from command prompt in order to include the derby jar.

Corba application using database

1 Answers