========================================================================================
JDK : java version "1.6.0-rc"
Java(TM) SE Runtime Environment (build 1.6.0-rc-b98)
Java HotSpot(TM) Client VM (build 1.6.0-rc-b98, mixed mode)
DB : JavaDB
Driver : JavaDB
Platform[s] : All
========================================================================================

When DataSet object is created using DataSource, a temporary connection is created and then closed. There is no check for DataSet being updatable/connected or not. This caused SQLRuntimeException to be thrown, when it should not.

OUTPUT:
-------
Inserts Holger, Wu & John
------- 1. query & loop
Found: Danske, Holger
Found: Doe, John
Found: Ming, Wu
Exception in thread "main" java.sql.SQLRuntimeException: Cannot update ResultSet column for dataset field type
       at com.sun.sql.DataSetImpl.insert(DataSetImpl.java:495)
       at EODdsClose.main(EODdsClose.java:81)
Caused by: java.sql.SQLTransientConnectionException: No current connection.
       at org.apache.derby.impl.jdbc.SQLExceptionFactory.getSQLException(Unknown Source)
       at org.apache.derby.impl.jdbc.SQLExceptionFactory40.wrapArgsForTransportAcrossDRDA(Unknown Source)
       at org.apache.derby.impl.jdbc.SQLExceptionFactory40.getSQLException(Unknown Source)
       at org.apache.derby.impl.jdbc.Util.newEmbedSQLException(Unknown Source)
       at org.apache.derby.impl.jdbc.Util.newEmbedSQLException(Unknown Source)
       at org.apache.derby.impl.jdbc.Util.noCurrentConnection(Unknown Source)
       at org.apache.derby.impl.jdbc.EmbedResultSet.checkExecIfClosed(Unknown Source)
       at org.apache.derby.impl.jdbc.EmbedResultSet.moveToInsertRow(Unknown Source)
       at com.sun.sql.DataSetImpl.insert(DataSetImpl.java:484)
       ... 1 more
Caused by: java.sql.SQLException: No current connection.
       ... 10 more

SOURCE:
-------
import java.sql.*;
import javax.sql.*;

public class EODdsClose
{
   static String DB = "/export/home//tmp/DB/eod";

   static public class Person {
       public Person() {
           // Needed for DataSet
           firstName = null;
           lastName = null;
       }
       public Person(String f, String l) {
           firstName = f;
           lastName = l;
       }
       public String firstName;
       @ResultColumn(uniqueIdentifier=true)
           public String lastName;
       public String toString()
       {
           if (firstName == null) {
               return lastName;
           } else {
               return lastName + ", " + firstName;
           }
       }
       public boolean equals(Person other)
       {
           if (firstName == null) {
               return lastName.equals(other.lastName);
           } else {
               return lastName.equals(other.lastName) &&
                   firstName.equals(other.firstName);
           }
       }
   }

   public static DataSource getDS()
       throws SQLException
   {
       org.apache.derby.jdbc.EmbeddedDataSource40 ds =
           new org.apache.derby.jdbc.EmbeddedDataSource40();

       // DatabaseName can include Derby URL Attributes
       ds.setDatabaseName(DB);
       ds.setCreateDatabase("create");

       return ds;
   }

   interface PersonQ extends BaseQuery {
       @Select(sql="select firstName, lastName from persons", readOnly=false)
           DataSet<Person> getPersons();
       @java.sql.Update(sql="delete from persons")
           int deleteAll();
       @java.sql.Update(sql="insert into persons values (?1,?2)")
           int insertPerson(String a, String b);
       @java.sql.Update(sql="create table persons (firstName varchar(256), lastName varchar(256), primary key(lastName,firstName))")
           int createTable();
   }

   static public void main(String []args)
       throws Exception
   {
       DataSource ds = getDS();
       PersonQ pqo = ds.createQueryObject(PersonQ.class);

       pqo.createTable();
       System.out.println("Inserts Holger, Wu & John");
       pqo.insertPerson("Holger","Danske");
       pqo.insertPerson("Wu","Ming");
       pqo.insertPerson("John", "Doe");

       System.out.println("------- 1. query & loop");
       DataSet<Person> dsp = pqo.getPersons();
       for (Person p: dsp) {
           System.out.println("Found: " + p);
       }
       dsp.insert(new Person("Ola","Nordmann"));

       dsp.close();

       System.out.println("------- 2. query & loop");
       dsp = pqo.getPersons();
       for (Person p: dsp) {
           System.out.println("Found: " + p);
       }
       dsp.close();
       pqo.close();
  }
}