Implementation

For information about the design and functionality of the MIDlet, see section Design.

To create the MIDlet:

1. Create the APDUMIDlet.java class file.

2. Import the required classes and packages.

   import javax.microedition.io.Connector;
   import javax.microedition.apdu.APDUConnection;
   import javax.microedition.midlet.*;
   import javax.microedition.lcdui.*;

3. Set APDUMIDlet to extend MIDlet and implement CommandListener and Runnable. MIDlets use the CommandListener interface to receive high-level UI events from the platform and the Runnable interface to execute threads.

   public class APDUMIDlet extends MIDlet implements CommandListener, Runnable {

4. Create the required variables, the APDUMIDlet class constructor, the MIDlet lifecycle methods, and the commandAction method for implementing CommandListener.

   When you pass a request to the Connector.open method to request an APDU connection, you need the apdu:0;target=a0.00.00.00.62.03.01.0c.02.01 locator string . The string identifies the slot number (0) and the card application identifier (a0.00.00.00.62.03.01.0c.02.01).

       private final String CardSlot0 = "apdu:0;target=a0.00.00.00.62.03.01.0c.02.01";
       private APDUConnection cardConnection0;
       private Display display;
       private Form mainForm;
       private Command exitCommand, demoCommand, backCommand;
       private Form progressForm;
   
       /** Constructor for the APDUMIDlet. Creates required commands and the form. */
       public APDUMIDlet() {
           exitCommand = new Command("Exit", Command.EXIT, 0);
           demoCommand = new Command("Demo", Command.SCREEN, 0);
           backCommand = new Command("Back", Command.BACK, 0);
   
           mainForm = new Form("APDU API Example");
           mainForm.append(" Press Demo to open smartcard connection.");
           mainForm.addCommand(exitCommand);
           mainForm.addCommand(demoCommand);
           mainForm.setCommandListener(this);
       }
   
       public void startApp() {
           display = Display.getDisplay(this);
           display.setCurrent(mainForm);
       }
   
       public void pauseApp() {
       }
   
       public void destroyApp(boolean unconditional) {
       }
   
       public void commandAction(Command c, Displayable s) {
           if (c == exitCommand) {
               notifyDestroyed();
           } else if (c == demoCommand) {
               progressForm = new Form("Opening connection ...");
               display.setCurrent(progressForm);
   
               Thread t = new Thread(this);
               t.start();
           } else if (c == backCommand) {
               display.setCurrent(mainForm);
           }
       }

5. Use the Connector.open method to pass a request to the Connector class. The class returns an object that is able to exchange data over the connection. Use the exchangeAPDU method to send a command to the card application and receive a response. To close the APDU connection, call the close method on the connection.

       public void run() {
           try {
               setProgress("Opening card at slot 0");
               cardConnection0 = (APDUConnection) Connector.open(CardSlot0);
   
               setProgress("Exchanging APDUs with card slot 0");
   
               byte[] response = cardConnection0.exchangeAPDU(kCardAPDU);
   
               progressForm.setTitle("Closing connection...");
   
               progressForm.setTitle("Done.");
   
               /** Converts bytes to string format. */
               String s = "";
               for (int j = 0; j < response.length; j++) {
                   int tmp = response[j];
                   if (tmp < 0) {
                       tmp += 256;
                   }
                   String tmps = Integer.toHexString(tmp);
                   if (tmps.length() == 1) {
                       tmps = "0" + tmps;
                   }
                   s += tmps + " ";
               }
   
               Form g = new Form("Response APDU:");
               g.append(s);
               g.addCommand(backCommand);
               g.setCommandListener(this);
               display.setCurrent(g);
           } catch (Exception e) {
               Form f = new Form("Exception");
               f.append(e.toString());
               f.addCommand(backCommand);
               f.setCommandListener(this);
               display.setCurrent(f);
           } finally {
               try {
                   cardConnection0.close();
               } catch (Throwable t) {
               }
           }
       }
   
       private void setProgress(String s) {
           StringItem si = new StringItem(null, s);
           si.setLayout(Item.LAYOUT_2 | Item.LAYOUT_NEWLINE_AFTER);
           progressForm.append(si);
       }

6. Define the APDU message as a byte array.

       /** A sample APDU. */
       private final byte[] kCardAPDU = // Select File EF_ID
               {(byte) 0x00, (byte) 0xA4, (byte) 0x08, (byte) 0x00,
           (byte) 0x02, (byte) 0x00, (byte) 0x03};
       // should return 01 90 00
   }