Executable Jar file: Not working after being embedded within a html page?

[Kieran Shoo]

Hello, I have a small problem with my applet when embedding within a html page.

The applet works fine when ran as a Jar Executable, yet when embedded into html (Even after being signed) it throws this error...

Using JRE version 1.6.0_17-b04 Java HotSpot(TM) Client VM
User home directory = C:\Users\Kieran
----------------------------------------------------
c:   clear console window
f:   finalize objects on finalization queue
g:   garbage collect
h:   display this help message
l:   dump classloader list
m:   print memory usage
o:   trigger logging
q:   hide console
r:   reload policy configuration
s:   dump system and deployment properties
t:   dump thread list
v:   dump thread stack
x:   clear classloader cache
0-5: set trace level to <n>
----------------------------------------------------
java.lang.reflect.InvocationTargetException
	at com.sun.deploy.util.DeployAWTUtil.invokeAndWait(Unknown Source)
	at sun.plugin2.applet.Plugin2Manager.runOnEDT(Unknown Source)
	at sun.plugin2.applet.Plugin2Manager.createApplet(Unknown Source)
	at sun.plugin2.applet.Plugin2Manager$AppletExecutionRunnable.run(Unknown Source)
	at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.RuntimeException: java.lang.InstantiationException: FileDownloader
	at sun.plugin2.applet.Plugin2Manager$12.run(Unknown Source)
	at java.awt.event.InvocationEvent.dispatch(Unknown Source)
	at java.awt.EventQueue.dispatchEvent(Unknown Source)
	at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
	at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
	at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
	at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
	at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
	at java.awt.EventDispatchThread.run(Unknown Source)
Caused by: java.lang.InstantiationException: FileDownloader
	at java.lang.Class.newInstance0(Unknown Source)
	at java.lang.Class.newInstance(Unknown Source)
	... 9 more
Exception: java.lang.reflect.InvocationTargetException
java.lang.NullPointerException
	at sun.plugin2.applet.Plugin2Manager.findAppletJDKLevel(Unknown Source)
	at sun.plugin2.applet.Plugin2Manager.createApplet(Unknown Source)
	at sun.plugin2.applet.Plugin2Manager$AppletExecutionRunnable.run(Unknown Source)
	at java.lang.Thread.run(Unknown Source)
Exception: java.lang.NullPointerException
java.lang.reflect.InvocationTargetException
	at com.sun.deploy.util.DeployAWTUtil.invokeAndWait(Unknown Source)
	at sun.plugin2.applet.Plugin2Manager.runOnEDT(Unknown Source)
	at sun.plugin2.applet.Plugin2Manager.createApplet(Unknown Source)
	at sun.plugin2.applet.Plugin2Manager$AppletExecutionRunnable.run(Unknown Source)
	at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.RuntimeException: java.lang.InstantiationException: FileDownloader
	at sun.plugin2.applet.Plugin2Manager$12.run(Unknown Source)
	at java.awt.event.InvocationEvent.dispatch(Unknown Source)
	at java.awt.EventQueue.dispatchEvent(Unknown Source)
	at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
	at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
	at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
	at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
	at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
	at java.awt.EventDispatchThread.run(Unknown Source)
Caused by: java.lang.InstantiationException: FileDownloader
	at java.lang.Class.newInstance0(Unknown Source)
	at java.lang.Class.newInstance(Unknown Source)
	... 9 more
Exception: java.lang.reflect.InvocationTargetException
java.lang.NullPointerException
	at sun.plugin2.applet.Plugin2Manager.findAppletJDKLevel(Unknown Source)
	at sun.plugin2.applet.Plugin2Manager.createApplet(Unknown Source)
	at sun.plugin2.applet.Plugin2Manager$AppletExecutionRunnable.run(Unknown Source)
	at java.lang.Thread.run(Unknown Source)
Exception: java.lang.NullPointerException
java.lang.reflect.InvocationTargetException
	at com.sun.deploy.util.DeployAWTUtil.invokeAndWait(Unknown Source)
	at sun.plugin2.applet.Plugin2Manager.runOnEDT(Unknown Source)
	at sun.plugin2.applet.Plugin2Manager.createApplet(Unknown Source)
	at sun.plugin2.applet.Plugin2Manager$AppletExecutionRunnable.run(Unknown Source)
	at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.RuntimeException: java.lang.InstantiationException: FileDownloader
	at sun.plugin2.applet.Plugin2Manager$12.run(Unknown Source)
	at java.awt.event.InvocationEvent.dispatch(Unknown Source)
	at java.awt.EventQueue.dispatchEvent(Unknown Source)
	at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
	at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
	at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
	at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
	at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
	at java.awt.EventDispatchThread.run(Unknown Source)
Caused by: java.lang.InstantiationException: FileDownloader
	at java.lang.Class.newInstance0(Unknown Source)
	at java.lang.Class.newInstance(Unknown Source)
	... 9 more
Exception: java.lang.reflect.InvocationTargetException
java.lang.NullPointerException
	at sun.plugin2.applet.Plugin2Manager.findAppletJDKLevel(Unknown Source)
	at sun.plugin2.applet.Plugin2Manager.createApplet(Unknown Source)
	at sun.plugin2.applet.Plugin2Manager$AppletExecutionRunnable.run(Unknown Source)
	at java.lang.Thread.run(Unknown Source)
Exception: java.lang.NullPointerException

The applet itself downloads files from an address to be loaded later from another program, without having to re-download everytime someone decides to use the other program. As stated before, running as an executable jar works perfectly fine. The applet is signed, and here is the source of a test html page to display the applet:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN">
<html>
<head>
<title>My Applet Page</html>
</head>

<body>
<applet code="FileDownloader.class" archive="Download.jar" width="400px" height="400px">
Java is not installed on your machine or your browser does not allowed Java Applet to run<br /><br />Get the latest Java technology at <a href="http://www.java.com/">http://www.java.com/</a>
</applet>
</body>
</html>

I don't believe there are any errors, the code will execute perfectly via executable jar or from the classes using a batch file.

Thanks for your time,
~Kieran

[Ulf Dittmer]

The applet works fine when ran as a Jar Executable, yet when embedded into html (Even after being signed) it throws this error...

An executable jar file depends on there being a class having a main method. An applet works rather differently - it needs to extend the Applet (or JApplet) class - does your FileDownloader class do that?

[Kieran Shoo]

Ulf Dittmer wrote:

The applet works fine when ran as a Jar Executable, yet when embedded into html (Even after being signed) it throws this error...

An executable jar file depends on there being a class having a main method. An applet works rather differently - it needs to extend the Applet (or JApplet) class - does your FileDownloader class do that?

I've fixed this now - thanks alot

[Paul Clapham]

It's not exactly a problem that your class has a main method. But when the browser goes to run your applet, it isn't going to call that main method. It wants to call some other methods, and that's where the problem arises. You should have a look at the Applet Tutorial to see what you should be doing instead.

[Kieran Shoo]

Ahh so instead of the main method I should be using the initialize method.

Thanks alot, i'll test to see if it works just now.
~Kieran

-Edit-

Alright, I replaced

public static void main(String[] args) {
		createFrame();
		initiateDownloads(multipleUrl.length, multipleUrl);
	}

With

public void init() {
        try {
            SwingUtilities.invokeAndWait(new Runnable() {
                public void run() {
                    createFrame();
					initiateDownloads(multipleUrl.length, multipleUrl);
                }
            });
        } catch (Exception e) { 
            System.err.println("Could not initialize applet");
        }
    }

However it still throws an error upon running the applet...

Java Plug-in 1.6.0_17
Using JRE version 1.6.0_17-b04 Java HotSpot(TM) Client VM
User home directory = C:\Users\Kieran
----------------------------------------------------
c:   clear console window
f:   finalize objects on finalization queue
g:   garbage collect
h:   display this help message
l:   dump classloader list
m:   print memory usage
o:   trigger logging
q:   hide console
r:   reload policy configuration
s:   dump system and deployment properties
t:   dump thread list
v:   dump thread stack
x:   clear classloader cache
0-5: set trace level to <n>
----------------------------------------------------


java.lang.reflect.InvocationTargetException
	at com.sun.deploy.util.DeployAWTUtil.invokeAndWait(Unknown Source)
	at sun.plugin2.applet.Plugin2Manager.runOnEDT(Unknown Source)
	at sun.plugin2.applet.Plugin2Manager.createApplet(Unknown Source)
	at sun.plugin2.applet.Plugin2Manager$AppletExecutionRunnable.run(Unknown Source)
	at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.RuntimeException: java.lang.InstantiationException: FileDownloader
	at sun.plugin2.applet.Plugin2Manager$12.run(Unknown Source)
	at java.awt.event.InvocationEvent.dispatch(Unknown Source)
	at java.awt.EventQueue.dispatchEvent(Unknown Source)
	at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
	at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
	at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
	at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
	at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
	at java.awt.EventDispatchThread.run(Unknown Source)
Caused by: java.lang.InstantiationException: FileDownloader
	at java.lang.Class.newInstance0(Unknown Source)
	at java.lang.Class.newInstance(Unknown Source)
	... 9 more
Exception: java.lang.reflect.InvocationTargetException
java.lang.NullPointerException
	at sun.plugin2.applet.Plugin2Manager.findAppletJDKLevel(Unknown Source)
	at sun.plugin2.applet.Plugin2Manager.createApplet(Unknown Source)
	at sun.plugin2.applet.Plugin2Manager$AppletExecutionRunnable.run(Unknown Source)
	at java.lang.Thread.run(Unknown Source)
Exception: java.lang.NullPointerException