Name: gm110360 Date: 03/12/2002


FULL PRODUCT VERSION :
java version "1.4.0"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.0-b92)
Java HotSpot(TM) Client VM (build 1.4.0-b92, mixed mode)


FULL OPERATING SYSTEM VERSION :

Windows 98 [Version 4.10.2222]

A DESCRIPTION OF THE PROBLEM :
JavaScript numeric variables are returned to Java applets
by the Java 2 Plug-in with an Integer object wrapper. I was
expecting a Double object wrapper, because that is what you
get when using the "LiveConnect" interface under both
Netscape Navigator 4.x and Microsoft Internet Explorer, when
using their vendor-specific Java 1.1 support. (Note,
however, that Netscape's LiveConnect documentation claims
that numeric variables are returned in a Float wrapper; but,
in fact, that has never been the case, it has always been a
Double wrapper in both Netscape's and Microsoft's
implementations.)

This discrepancy causes existing LiveConnect applets to
crash, as they are coded to use a cast to Double, which
fails. A typical line of code is:

rows = ((Double)screen.getMember("rows")).intValue();

  To get this to work with the Java 2 Plug-in, one can change
the code to:

rows = ((Integer)screen.getMember("rows")).intValue();

But then the applet will crash when run under older Web
browsers. However, there is a (rather awkward) "workaround"
which makes the code work in all cases. (See below.)

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
1. Code an applet and a Web page. The Web page must use
JavaScript to set some JavaScript variables and the Java
applet must issue "LiveConnect" calls to "getMember" to
retrieve the value of a numeric JavaScript variable.

2. Install the applet and Web page on a Web server.

3. Use a browser to access the Web page with the test
applet. Be sure the Java Console is activated.

4. Test the applet.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED:

The value of the numeric JavaScript variable is successfully
retrieved by the Java application.

ACTUAL:

The applet crashes, because it is coded to cast the returned
object to an object type that is different from what is
actually received.

ERROR MESSAGES/STACK TRACES THAT OCCUR :
java.lang.ClassCastException: java.lang.Integer
at kb.init(kb.java:459)
at sun.applet.AppletPanel.run(AppletPanel.java:341)
at java.lang.Thread.run(Thread.java:536)


This bug can be reproduced always.

---------- BEGIN SOURCE ----------
import java.applet.Applet;
import java.awt.event.*;
import java.awt.Graphics;
import netscape.javascript.JSObject;

public class wraptest extends Applet implements KeyListener
  {
  JSObject win;

  public void init()
    {
    win = JSObject.getWindow(this);
    get_javascript_boolean();
    get_javascript_int();
    get_javascript_float();
    get_javascript_string();
    this.addKeyListener(this);
    }

  public void start()
    {
    requestFocus();
    }

  public void stop()
    {
    }

  public void paint(Graphics g)
    {
    requestFocus();

    // Draw a Rectangle around the applet's display area.

    g.drawRect(0, 0, getSize().width - 1, getSize().height - 1);
    }

  public void keyPressed(KeyEvent e)
    {
    int key = e.getKeyCode();

    if (KeyEvent.VK_F1 <= key && key <= KeyEvent.VK_F12)
      {
      System.out.println("F" + (key + 1 - KeyEvent.VK_F1) + " key pressed.");
      if (e.getKeyCode() == KeyEvent.VK_F9)
        {
        win.eval("ShowDecision()");
        get_javascript_boolean();
        requestFocus();
        }
      else if (e.getKeyCode() == KeyEvent.VK_F10)
        {
        win.eval("ShowAnswer()");
        get_javascript_int();
        requestFocus();
        }
      else if (e.getKeyCode() == KeyEvent.VK_F11)
        {
        win.eval("ShowPi()");
        get_javascript_float();
        requestFocus();
        }
      else if (e.getKeyCode() == KeyEvent.VK_F12)
        {
        win.eval("ShowMsg()");
        get_javascript_string();
        requestFocus();
        }
      e.consume();
      }
    }

  public void keyTyped(KeyEvent e)
    {
    }

  public void keyReleased(KeyEvent e)
    {
    }

  void get_javascript_boolean()
    {
    Object obj;
    Boolean b;

    obj = win.getMember("decision");
    if (obj != null)
      {
      System.out.println("\"decision\" returned wrapped as a " + obj.getClass().getName());
      try
        {
        b = (Boolean)obj.getClass().getMethod("booleanValue", null).invoke(obj, null);
        System.out.println("\"decision\" value is " + b.booleanValue());
        }
      catch (Exception e)
        {
        System.out.println("Could not convert \"decision\" to a \"boolean\"!");
        }
      }
    else
      System.out.println("\"decision\" is null!");
    }

  void get_javascript_int()
    {
    Object obj;
    Integer i;

    obj = win.getMember("answer");
    if (obj != null)
      {
      System.out.println("\"answer\" returned wrapped as a " + obj.getClass().getName());
      try
        {
        i = (Integer)obj.getClass().getMethod("intValue", null).invoke(obj, null);
        System.out.println("\"answer\" value is " + i.intValue());
        }
      catch (Exception e)
        {
        System.out.println("Could not convert \"answer\" to an \"int\"!");
        }
      }
    else
      System.out.println("\"answer\" is null!");
    }

  void get_javascript_float()
    {
    Object obj;
    Double d;

    obj = win.getMember("pi");
    if (obj != null)
      {
      System.out.println("\"pi\" returned wrapped as a " + obj.getClass().getName());
      try
        {
        d = (Double)obj.getClass().getMethod("doubleValue", null).invoke(obj, null);
        System.out.println("\"pi\" value is " + d.doubleValue());
        }
      catch (Exception e)
        {
        System.out.println("Could not convert \"pi\" to a \"double\"!");
        }
      }
    else
      System.out.println("\"pi\" is null!");
    }

  void get_javascript_string()
    {
    Object obj;
    String s;

    obj = win.getMember("msg");
    if (obj != null)
      {
      System.out.println("\"msg\" returned wrapped as a " + obj.getClass().getName());
      try
        {
        s = (String)obj.getClass().getMethod("toString", null).invoke(obj, null);
        System.out.println("\"msg\" value is \"" + s.toString() + "\"");
        }
      catch (Exception e)
        {
        System.out.println("Could not convert \"msg\" to a \"String\"!");
        }
      }
    else
      System.out.println("\"msg\" is null!");
    }
  }

<HTML>
<HEAD>
<TITLE>JavaScript Variable Wrapper Test</TITLE>
</HEAD>
<SCRIPT>
var decision = true;
var answer = 42;
var pi = 3.14159;
var msg = "This is a test";

function ShowDecision()
  {
  alert("JavaScript variable \"decision\" is " + decision);
  }
function ShowAnswer()
  {
  alert("JavaScript variable \"answer\" is " + answer);
  }
function ShowPi()
  {
  alert("JavaScript variable \"pi\" is " + pi);
  }
function ShowMsg()
  {
  alert("JavaScript variable \"msg\" is \"" + msg + "\"");
  }
</SCRIPT>
<BODY>
Applet's Sandbox:
<P>
<APPLET MAYSCRIPT CODE="wraptest.class" WIDTH=64 HEIGHT=48>
</APPLET>
</BODY>
</HTML>

---------- END SOURCE ----------

CUSTOMER WORKAROUND :
Object obj = screen.getMember("rows");
try
  {
  rows =
(char)((Integer)obj.getClass().getMethod("intValue",
null).invoke(obj, null)).intValue();
  }
catch (Exception ex)
      {
      }
(Review ID: 143976)
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