Sharing Objects between Applets...

Hi,

You can share objects as long as they are also shareable objects. For this they do not need to be an applet, just have an interface that extends Shareable.

Here is an example of a User class that is shareable like this

public interface SharedUser extends Shareable {

    /**
     * @return the id
     */
    public short getId();

    /**
     * @return the name
     */
    public short getName(byte[] buf, short off);

}

public class User implements SharedUser {
    private static short count = 1;
    private short id;
    private byte[] name;

    /**
     * 
     */
    public User() {
        id = count++;
        name = new byte[] { 'S', 'h', 'a', 'n', 'e' };
    }

    /* (non-Javadoc)
     * @see oracle.other.SharedUser#getId()
     */
    public short getId() {
        return id;
    }

    /* (non-Javadoc)
     * @see oracle.other.SharedUser#getName(byte[], short)
     */
    public short getName(byte[] buf, short off) {
        return Util.arrayCopy(name, (short) 0, buf, off, (short) name.length);
    }
}

public interface SharedAccess extends Shareable {
    public SharedUser getUser();
}

public class AccessApplet extends Applet implements SharedAccess {

    public static void install(byte[] bArray, short bOffset, byte bLength) {
        // GP-compliant JavaCard applet registration
        new AccessApplet().register(bArray, (short) (bOffset + 1), bArray[bOffset]);
    }

    /*
     * (non-Javadoc)
     * 
     * @see javacard.framework.Applet#select()
     */
    public boolean select() {
        return false;
    }

    public void process(APDU apdu) {
        return;
    }

    /*
     * (non-Javadoc)
     * 
     * @see javacard.framework.Applet#getShareableInterfaceObject(javacard.framework.AID, byte)
     */
    public Shareable getShareableInterfaceObject(AID clientAID, byte parameter) {
        return this;
    }

    /*
     * (non-Javadoc)
     * 
     * @see oracle.other.SharedAccess#getUser()
     */
    public SharedUser getUser() {
        return new User();
    }

}

You can add a method to your main SOI to return the shareable interface (SharedUser in this case) and then use that in your client applet. Be aware that the only way to get a byte array across a SOI is using the APDU buffer to copy. You will notice the getName method of the shared user takes an array rather than returning the array. The copy happens in the server context and the server is allowed to access the APDU buffer as it is global. If you return the name buffer or pass a buffer from the server you will get a security exception.

Cheers,
Shane

Edited by: safarmer on 13/07/2011 13:39

Removed duplicate post as the forum wasn't posting my reply. I guess it did. Thanks Oracle : )

Edited by: safarmer on 13/07/2011 13:43

Dear,

You are using process(APDU apdu) method to get a global array which can be passed between applets. But I am developing a Telecom application, it is triggered by event through processToolkit(byte event)  method, so the applet will not receive any apdu, then how can I get the APDU buffer?             Thank you very much!