Oracle8i Enterprise JavaBeans Developer's Guide and Reference
Release 3 (8.1.7)
Part Number A83725-01

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Invoking EJB Objects From Applets

You invoke a server object from an applet in the same manner as from a client. The only differences are the following:

Using Signed JAR Files to Conform to Sandbox Security

The security sandbox constricts your applet from accessing anything on the local disk or from connecting to a remote host other than the host that the applet was downloaded from. If you create a signed JAR file as a trusted party, you can bypass the sandbox security. See http://java.sun.com for more information on applet sandbox security and signed JAR files.

Performing Object Lookup in Applets

You perform the JNDI lookup within the applet the same as within any Oracle Java client, except that you set the following property within the initial context: 

env.put(ServiceCtx.APPLET_CLASS, this);

By default, you do not need to install any JAR files on the client to run the applet. However, if you want to place the Oracle JAR files on the client machine, set the ClassLoader property in the InitialContext environment, as follows: 

env.put('ClassLoader', this.getClass().getClassLoader());

The following shows the init method within an applet that invokes the Bank example. The applet sets up the initial context--including setting the
APPLET_CLASS property--and performs the JNDI lookup giving the URL. 

public void init() {
    // This GUI uses a 2 by 2 grid of widgets.
    setLayout(new GridLayout(2, 2, 5, 5));
    // Add the four widgets.
    add(new Label("Account Name"));
    add(_nameField = new TextField());
    add(_checkBalance = new Button("Check Balance"));
    add(_balanceField = new TextField());
    // make the balance text field non-editable.
    _balanceField.setEditable(false);
    try {
      // Initialize the ORB (using the Applet).
      Hashtable env = new Hashtable();
      env.put(Context.URL_PKG_PREFIXES, "oracle.aurora.jndi");
      env.put(Context.SECURITY_PRINCIPAL, "scott");
      env.put(Context.SECURITY_CREDENTIALS, "tiger");
      env.put(Context.SECURITY_AUTHENTICATION, ServiceCtx.NON_SSL_LOGIN);
      env.put(ServiceCtx.APPLET_CLASS, this);

      Context ic = new InitialContext(env);
      _manager = (AccountManager)ic.lookup 

	("sess_iiop://hostfunk:2222/test/myBank");
    } catch (Exception e) {
      System.out.println(e.getMessage());
      e.printStackTrace();
      throw new RuntimeException();
    }
  }

Within the action method, the applet invokes methods off of the retrieved object. In this example, the open method of the retrieved AccountManager object is invoked. 

  public boolean action(Event ev, Object arg) {
    if(ev.target == _checkBalance) {
      // Request the account manager to open a named account.
      // Get the account name from the name text widget.
      Bank.Account account = _manager.open(_nameField.getText());
      // Set the balance text widget to the account's balance.
      _balanceField.setText(Float.toString(account.balance()));
      return true;
    }
    return false;
  }

Modifying HTML for Applets that Access EJB Objects

Oracle8i supports only the following Java plug-ins for the HTML page that loads in the applet: JDK 1.1, Java 2, and Oracle JInitiator. Each plug-in contains different syntax for the applet information. However, each HTML page may contain definitions for the following two properties:

The examples in the following sections show how to create the correct HTML definition for each plug-in type. Each HTML definition defines the applet bank example.

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