executing java method with dependencies inside a dynamically loaded class

I have my jar file with its own libs like any other netbeans project. Additionally I have a "plugins" folder to store plugins in a .jar file format. I´m loading the plugins using an URLClassLoader and I´m also executing the proper method without any problem.

However, the jar f开发者_运维技巧ile in the plugins folder may contain dependencies with other packages (java-mail, for example) who aren´t in my classpath (the plugins folder isn´t in my classpath neither), so I´m worried whether that plugin would be executed correctly. I also don´t know where I should store that dependency.

Could I do something to overcome this issue? Where should I store the plugin dependency?

Thanks.

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The ClassLoader class uses a delegation model to search for classes and resources. Each instance of ClassLoader has an associated parent class loader. When requested to find a class or resource, a ClassLoader instance will delegate the search for the class or resource to its parent class loader before attempting to find the class or resource itself. The virtual machine's built-in class loader, called the "bootstrap class loader", does not itself have a parent but may serve as the parent of a ClassLoader instance.

(From the javadoc of ClassLoader)

The paragraph above means that normally, your class loaders form a tree and each one asks its parent before trying to load a class. So in theory, if your dependencies are visible by either the class loader that is loading the plugin, or any of the upstream class loaders, it will work.

However, there are two caveats with this:

1. If your plugin calls Thread.setContextClassLoader(), that might mess things up. But this should be more of the plugin writers' concern rather than yours.
2. Web servers typically don't obey this delegation rule to ensure maximum separation between different webapps and the server itself.

(I could probably give a less generic answer if there was some code I could look at.)

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According to biziclop, i have put the dependencies inside the plugin folder. It seems to work, but i have needed to download extra packages.

To clarify, i made a plugin using the apache httpClient library. I made the jar file, and then i put the jar file with its dependencies (httpClient and httpCore) inside the plugin folder. When i executed the plugin a "NoClassDefFoundError" appeared. To overcome this issue i have download the "commons-logging" and "servlet" packages and i have added them into the plugin folder.

At least, that´s not my problem because the plugin developer should test the plugin and provide those extra packages, but the fact is that those extra packages are unveiled while testing the plugin and not while compiling it.

Thanks for the help!