Execute parameterized PL SQL procedure from OAF page

import oracle.apps.fnd.framework.server.OADBTransaction;
import oracle.apps.fnd.framework.server.OADBTransactionImpl;
import oracle.jdbc.OracleCallableStatement;
import java.sql.Types;
import oracle.apps.fnd.framework.OAException;
...

public String dataSumAction(String item1,String item2)
{ OADBTransaction oadbtransaction = (OADBTransaction)getTransaction();   OADBTransactionImpl oadbtransactionimpl = (OADBTransactionImpl)getTransaction();

 String retValues;

 StringBuffer str = new StringBuffer();
 str.append( " BEGIN ");
 str.append( " test_package.data_sum( ");
 str.append( "       item1           => :1, ");
 str.append( "       item2           => :2, ");  str.append( "       data_sum    => :3  ");
 str.append( "    ); ");
 str.append( " END; ");

 OracleCallableStatement oraclecallablestatement =
  (OracleCallableStatement)oadbtransaction.createCallableStatement(str.toString(), 1);

 try{
  oraclecallablestatement.setInt(1,  Integer.parseInt(item1) );
  oraclecallablestatement.setInt(2,  Integer.parseInt(item2) );

  oraclecallablestatement.registerOutParameter(3, Types.VARCHAR);

  oraclecallablestatement.execute();
                   
  retValues = oraclecallablestatement.getString(3);
 }  catch(Exception e)
 {
  throw OAException.wrapperException(e);
 }
 return retValues;
}

========================================================================

 public void testStoredProcedure() { 

  

     OADBTransaction txn = getDBTransaction();  

     CallableStatement callableStatement =txn.createCallableStatement("begin mmm_procedure(:1, :2); end;",OADBTransaction.DEFAULT);  

     try 

      {  

       callableStatement.registerOutParameter(2, Types.VARCHAR);  

       callableStatement.setString(1, "mahi");  

       String outParamValue = null;  

       callableStatement.execute();  

       outParamValue = callableStatement.getString(1);  

       callableStatement.close();  

     } 

     catch (SQLException sqle) 

     {  

       callableStatement.close(); 

     } 

   }