[2128] in java-interest
Re: class loaders
daemon@ATHENA.MIT.EDU (Chuck McManis)
Mon Sep 25 22:48:37 1995
Date: Mon, 25 Sep 1995 17:05:12 -0700
From: cmcmanis@scndprsn.Eng.Sun.COM (Chuck McManis)
To: java-interest@java.Eng.Sun.COM, jpayne@starwave.com
>Can I define my own class loader which loads classes from the file
>system?
Yes.
> ... If I do, will I be subject to the security measures which are
>in place for WWWClassLoader, which loads classes from the network?
In alpha3 yes.
> ... Or
>are the security measures dependent on that particular class loader
>subclass?
In Beta the security measures are implemented by a "SecurityManager".
There is a subclass of SecurityManager called AppletSecurity that defines
the policies for applets.
If you are an applet, the AppletClassloader will not let you instantiate
a new class loader. If you are simply a Java program you have the option
to call the security manager in your loadClass method if you so choose.
>Also, if my class loader periodically checks the file system for an
>update to that class, and reloads that class, will the system actually
>successfully start using the new definition of the class. Something
>tells me that it will actually continue to use the original
>definition, because the class is actually stored internally in the
>interpreter.
Your latter statement is the more correct one. It is of course possible
to define a native method in your class loader that does a manual substitution
on the internal class list however that is probably a fairly dangerous
operation, especially if you make an incompatible class change.
--Chuck
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