I've talked this over with the big Guns of Avalon, some month back and tried a couple
of suggested
solutions (including thread context based ones), but nothing worked for the unique
situation I had
at the time.
The problem re-interated is that Jesktop (block) mounts many of it's own classloaders
for
hot-installable and hot-upgradable apps. Some of them want to persist data, and the
persistence
store is the obvious place to do it. The trouble is that a ClassNotFoundException was
always
thrown because the Store couldn't work out which of the ten or so different
classloaders had the
definition of the class. Thread.setContextClassLoader(..) didn't work either.
What was tested at the time, but objected to because of inelegance was a way of
passing in the
classloader for use _during_ the internal store code to deserialize objects. I tested
it and it
worked, but under pressure from said guns, tried other things. Then I moved
countries, jobs, went
on a diet and saw thru a heavy winter ;-) Now, older and wiser, I'd like to
re-propose a tuned
additonal get() method for store:
1) ObjectRepository (interface ) -> new method ->
Object get( String key , ClassLoader classLoader );
2) File_Persistent_Object_Repository (class) new method :
public synchronized Object get( final String key , final ClassLoader classLoader )
{
......
}
3) File_Persistent_Object_Repository (class) new inner class :
/**
* A special ObjectInputStream to handle highly transient classes hosted by Avalon
components
* that are juggling many classloaders.
*/
private class FileStoreObjectInputStream extends ObjectInputStream
{
private ClassLoader classLoader;
private FileStoreObjectInputStream(ClassLoader classLoader, InputStream in)
throws IOException, StreamCorruptedException
{
super(in);
this.classLoader = classLoader;
}
protected Class resolveClass(ObjectStreamClass v)
throws IOException, ClassNotFoundException
{
Class cl = Class.forName(v.getName(), false, classLoader);
if (cl !=null)
{
return cl; // the classloader knows of the class
}
else
{
// classloader knows not of class, let the super classloader do it.
return super.resolveClass(v);
}
}
}
What's thought of this?
=====
Regards - Paul H
====
CVS -1, Perforce +1
__________________________________________________
Do You Yahoo!?
Get email at your own domain with Yahoo! Mail.
http://personal.mail.yahoo.com/
---------------------------------------------------------------------
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
