RE: injecting code into java.* classes

[Peter Schneider <sc...@lathanda.de>]

Hi

[...]
> This took care of the security exception and it returned a 
> Class object. However, when I tried to instantiate the URL 
> object, I get this error:
> java.lang.IllegalAccessError: try to access method 
> java.net.URLStreamHandler.parseURL(Ljava/net/URL;Ljava/lang/St
> ring;II)V from class java.net.URL at 
> java.net.URL.<init>(URL.java:145) at 
> java.net.URL.<init>(URL.java:76) at 
> java.net.URL.<init>(URL.java:70) at 
> net.nvisionsoftware.DynamicJavaMon.gui.T2.main(T2.java:30)
> 
> Any idea what's going on or how I can actually inject code 
> into java.* classes? Thanks,
I suppose wrong classloader!
The class your code wants to access was loaded by the system
classloader.
Which means it isn't in the same namespace and therefore it isn't
allowed to access these members.

Btw, I really hope there is no way to inject such code, during runtime.

Peter



--
To unsubscribe, e-mail:   <ma...@jakarta.apache.org>
For additional commands, e-mail: <ma...@jakarta.apache.org>

Re: injecting code into java.* classes

[Juozas Baliuka <ba...@mwm.lt>]

Hi,
You can use reflection to call private
methods(java.lang.reflect.AccessibleObject), or to try find
some better solutions for problems.


> Hi
>
> [...]
> > This took care of the security exception and it returned a
> > Class object. However, when I tried to instantiate the URL
> > object, I get this error:
> > java.lang.IllegalAccessError: try to access method
> > java.net.URLStreamHandler.parseURL(Ljava/net/URL;Ljava/lang/St
> > ring;II)V from class java.net.URL at
> > java.net.URL.<init>(URL.java:145) at
> > java.net.URL.<init>(URL.java:76) at
> > java.net.URL.<init>(URL.java:70) at
> > net.nvisionsoftware.DynamicJavaMon.gui.T2.main(T2.java:30)
> >
> > Any idea what's going on or how I can actually inject code
> > into java.* classes? Thanks,
> I suppose wrong classloader!
> The class your code wants to access was loaded by the system
> classloader.
> Which means it isn't in the same namespace and therefore it isn't
> allowed to access these members.
>
> Btw, I really hope there is no way to inject such code, during runtime.
>
> Peter
>
>
>
> --
> To unsubscribe, e-mail:
<ma...@jakarta.apache.org>
> For additional commands, e-mail:
<ma...@jakarta.apache.org>


--
To unsubscribe, e-mail:   <ma...@jakarta.apache.org>
For additional commands, e-mail: <ma...@jakarta.apache.org>

Re: injecting code into java.* classes

[Abel Wang <ab...@nvisionsoftware.net>]

Is the system class loader different than java.lang.ClassLoader (which is
where I'm attempting the injection)?  Sorry, I'm not as well versed with
ClassLoaders as I should be.  How does java determine name space?  If I
don't "inject" into URL, it can call
java.net.URLStreamHandler.parseURL(Ljava/net/URL;Ljava/lang/String;II).  If
I inject a simple println statement in the constructor, it can't.  Does that
mean that since I injected into the code, another class loader (not the
System class loader) loaded the class and therefore it can't access the
protected method in URLStreamHandler?   So if different class loaders load
the classes, even if they have the same package name, they are considered
different name spaces?  How does java determine namespace?

Hmmmm.... ok, here's another question.  Inside of java.lang.ClassLoader,
when someone asks for a class, it asks the parent class loader to load the
class, and then, java.lang.ClassLoader returns the class.  Where is this
class stored when it is "loaded into memory"

Once again, sorry for the stupid questions.  I'm just trying to get a handle
on how the class loader works in java.


And why do you hope there is no way to inject code into core java classes at
runtime?  Besides the huge potential for messing up core java classes?

Thanks,

--Abel
----- Original Message -----
From: "Peter Schneider" <sc...@lathanda.de>
To: "'BCEL Users List'" <bc...@jakarta.apache.org>
Sent: Monday, August 12, 2002 10:15 AM
Subject: RE: injecting code into java.* classes


> I suppose wrong classloader!
> The class your code wants to access was loaded by the system
> classloader.
> Which means it isn't in the same namespace and therefore it isn't
> allowed to access these members.
>
> Btw, I really hope there is no way to inject such code, during runtime.
>
> Peter
>
>
>
> --
> To unsubscribe, e-mail:
<ma...@jakarta.apache.org>
> For additional commands, e-mail:
<ma...@jakarta.apache.org>
>
>


--
To unsubscribe, e-mail:   <ma...@jakarta.apache.org>
For additional commands, e-mail: <ma...@jakarta.apache.org>