Re: Loading plugins

=?ISO-8859-1?Q?Arne_Vajh=F8j?= <>
Wed, 06 Oct 2010 14:29:34 -0400
On 06-10-2010 13:21, Spud wrote:

My app is extendable via "plugins". A plugin is a .jar file that adds
some functionality to the app. The idea is that the user can copy new
jar files to a subdirectory, restart the app, and the new functionality
is available.

Here's the tricky issue: to get all the jar files on the classpath, we
have to do one of two things:

1. Write an unpleasant startup script that will roll through all the
subdirectories, find the jars, and add them to the -classpath string on
the java command line. I say "unpleasant" because this isn't a pure java
solution and will have to be customized for each platform.

2. Find some way to do this with classloaders after the app has started.

I'd prefer the second approach, but I fear classloader hell and can't be
sure the code would be reliable.

What's the best approach here?

I would go for #2.

This is what tons of app servers and standalone apps do.

It works.

You will of course need to know a little bit about classloading,
but ...


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