----- Original Message -----
From: Kathey Marsden <[EMAIL PROTECTED]>
Date: Monday, November 14, 2005 7:51 pm
Subject: Re: Question about using URLClassLoader and Derby
To: Derby Discussion <[email protected]>
Cc: Binod P G <[EMAIL PROTECTED]>
> I am moving this to derby-dev as I think my new questions are more
> appropriate for this list.
> Oyvind's suggestion to make a DerbyURLClassLoader to filter out the
> derby classes from the parent class loader all seems to be working ok
> (with some very minimal testing).
>
>
> David W. Van Couvering wrote (for Binod):
>
> >Make sure that there is only one URL classloader instance that has
> >access to the derby jar files. And make sure that whenever a code
> >accesses the datasource, it always go thru newDataSource method, then
> >yes, it should work.
> >
> >
> >
>
> I just want to verify that this just means that my app should use the
> same loader if it needed to get another datasource for say shutting
> downthe database. Other applications should be able to use their own
> DerbyURLClassLoaders to access Derby as long as they are accessing
> different databases, right?
Yes. It is also possible that two parts of same application want to create two
datasource instances.
BTW, where would your application run? I am assuming it is outside of
any managed environment like application server.
- Binod.
>
> >- Binod.
> >
> >p.s: This is all assuming that derby code doent do any other
> interesting>classloader mechanism inside :-). For example, it can
> use Thread's
> >context classLoader to load some other part of derby that might
> break.>
> >
> >
> Is there anything like Binod describes in Derby that might cause
> problems (e.g. code for loading generated byte code, loading databases
> from jars or aggregates) ?
>
> One other issue I have encountered is that I am not sure how to
> handlethe derby error log (derby.log). The configuration for
> this is only
> provided with System properties or entries in the derby.properties
> filewhich would affect other apps. How do I create my own isolated
> errorlog with out clobbering the error logs of other apps or having
> themclobber mine?
>
> Thanks
>
> Kathey
>
>
> Below is the DerbyURLClassLoader loadClass method for reference.
>
> /* Override the parent class loader to filter out any derby
> * jars in the classpath. Any classes that start with
> * "org.apache.derby" will load from the URLClassLoader
> *
> * @see java.lang.ClassLoader#loadClass(java.lang.String, boolean)
> */
> protected Class loadClass(String name, boolean resolve)
> throws ClassNotFoundException
> {
> // This code and a approach were suggeted by Knut Anders
> Hatlen and
> // Oyvind Bakksjo on the derby-user list.
> Class cl = findLoadedClass(name);
> if (cl == null) {
> // cut off delegation to parent for certain classes
> // to ensure loading from the desired source
> if (!name.startsWith("org.apache.derby")) {
> cl = getParent().loadClass(name);
> }
> }
> if (cl == null) cl = findClass(name);
> if (cl == null) throw new ClassNotFoundException();
> if (resolve) resolveClass(cl);
> return cl;
> }
>
>
>
>
>
>
