Sharing an applet with another dosn't function

Question

Hi all,
i have a problem that i share an applet with another, but it dosn't function:
i have two applet: epurse & bank   (bank is the master)
for that i creat a class "bankInterface" that's inherit from sharable:
package pack4;
import javacard.framework.APDU;
import javacard.framework.Shareable;
public interface bankInterface extends Shareable {
  public void debit(APDU apdu);
bank's declaration:
public class bank extends Applet implements bankInterface {
public Shareable getShareableInterfaceObject (AID clientAID, byte param){
  return ((bankInterface)this);  //or return this;
public  void deselect(){
      pin.reset();
  public boolean select() {
       return super.select();
  public static void install(byte bArray[], short bOffset, byte bLength) throws ISOException {
       new bank();
private bank() {
  register();
public void process(APDU apdu) throws ISOException {
public void debit(APDU apdu){
//empty juste for testing
}// end class 'bank'
epurse's declaration:
package pack4;
import ...
public class epurse extends Applet {
byte[] AIDServer=new byte[]{0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x00, 0x00, 0x00};
public bankInterface sio;
private epurse() {
  sio=(bankInterface) JCSystem.getAppletShareableInterfaceObject(JCSystem.lookupAID(AIDServer, (short)0, (byte)AIDServer.length), (byte)0);
//methods: install, select, deselect
public void process(APDU apdu) throws ISOException {
byte[] apduBuffer=apdu.getBuffer()
if(apduBuffer[ISO7816.OFFSET_CLA] == (byte)0x80){
  switch(apduBuffer[ISO7816.OFFSET_INS]){
  case (byte)0x34:
  credit(apdu);break;
else{ ...}
}//end process
private void credit(APDU apdu){
apdu.setIncomingAndReceive();
sio.debit(apdu); // if this line is commented, i get the sw1:90 sw2: 00; else i get sw1: 6f sw2: 00 (wrong length)
}// end class epurse
i don't know where's the problem?

Answer 1

Hi,
If you go through the SIO concepts of JavaCard its mentioned that when "getAppletShareableInterfaceObject" is called from the client the JCRE will call "getShareableInterfaceObject" method of server with clientAID but where as you are requesting for SIO in install method before registration where the clientAID doesnt exists so the call will fail and return "null" and further references to SIO object will fail to perform expected operations.
So put request for SIO after registration of your client applet.
BR,
PPT