Here's an answer from Binod, one of our app server engineers...
Kathey Marsden wrote:
My goal is:
I want to use a specific version of Derby which I ship with my app and I
don't want to interfere with any other derby versions loaded in the
same JVM or have them interfere with me. I am creating a new
datasource in a separate URLClassLoader and using that for creating all
my connections. Are there other things I need to do to meet my goal?
I have a feeling it all must be more complex than it looks to me right now.
Thanks
Kathey
Below is some code showing what I have done in playing with this so far.
Method to load derby in separate loader and create datasource:
private static DataSource newDataSource(ClassLoader loader, String
databaseName) throws Exception
{
DataSource ds = (DataSource)
loader.loadClass("org.apache.derby.jdbc.EmbeddedDataSource").newInstance();
// setDatabaseName with reflection
Class[] argType = {String.class};
String[] args = new String[] {databaseName};
Method sh = ds.getClass().getMethod("setDatabaseName", argType);
sh.invoke(ds, args);
return ds;
}
// Calling program ....
.....
URL[] urls =
new URL[]{new URL(derbyJarURLString)};
System.out.println(urls[0].getFile());
ClassLoader loader1 =new URLClassLoader(urls);
DataSource ds = newDataSource(loader1,"mydb;create=true");
ds.getConnection();
...
--- Begin Message ---
David W. Van Couvering wrote On 11/09/05 10:51 PM,:
> Hi, guys. Is there any helpful information you can provide Kathey? You
> can respond to me or directly to [EMAIL PROTECTED] If you load
> one class with a classloader, will all other classes for objects created
> by that class be loaded from the same classloader? If not, how do you
> achieve what she is trying to accomplish?
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.
- 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.
>
> Thanks!
>
> David
>
>
> ------------------------------------------------------------------------
>
> Subject:
> Question about using URLClassLoader and Derby
> From:
> Kathey Marsden <[EMAIL PROTECTED]>
> Date:
> Wed, 09 Nov 2005 08:55:58 -0800
> To:
> Derby Discussion <[email protected]>
>
>
> My goal is:
> I want to use a specific version of Derby which I ship with my app and I
> don't want to interfere with any other derby versions loaded in the
> same JVM or have them interfere with me. I am creating a new
> datasource in a separate URLClassLoader and using that for creating all
> my connections. Are there other things I need to do to meet my goal?
> I have a feeling it all must be more complex than it looks to me right now.
>
> Thanks
>
> Kathey
>
> Below is some code showing what I have done in playing with this so far.
>
> Method to load derby in separate loader and create datasource:
>
> private static DataSource newDataSource(ClassLoader loader, String
> databaseName) throws Exception
> {
> DataSource ds = (DataSource)
> loader.loadClass("org.apache.derby.jdbc.EmbeddedDataSource").newInstance();
> // setDatabaseName with reflection
> Class[] argType = {String.class};
> String[] args = new String[] {databaseName};
> Method sh = ds.getClass().getMethod("setDatabaseName", argType);
> sh.invoke(ds, args);
> return ds;
>
> }
>
> // Calling program ....
> .....
> URL[] urls =
> new URL[]{new URL(derbyJarURLString)};
> System.out.println(urls[0].getFile());
> ClassLoader loader1 =new URLClassLoader(urls);
> DataSource ds = newDataSource(loader1,"mydb;create=true");
> ds.getConnection();
> ...
>
>
>
--
--- End Message ---
begin:vcard
fn:David W Van Couvering
n:Van Couvering;David W
org:Sun Microsystems, Inc.;Database Technology Group
email;internet:[EMAIL PROTECTED]
title:Senior Staff Software Engineer
tel;work:510-550-6819
tel;cell:510-684-7281
x-mozilla-html:TRUE
version:2.1
end:vcard
