Dynamic class reloading in modular web application

Question

Hi.
My web application has these requirements:
A. Functional modularization (like plug-ins). Modules will be simple jars containing application logic classes: dto beans, business logic services, dao (jpa), framework stuff (Struts2), etc...
B. At runtime and without restarting the application "class loading" must be aware of classes inside new, changed and removed modules.
C. Some of these jars will be outside the web application folder (WEB-INF/lib), possibly outside the container itself too.
My question:
1. Can I achieve all or some of my requirements with a Java web application?
2. How should I manage the modules?
3. Do I need some special web container feature (maybe osgi)?
4. Can I use a custom class loader in my application?
The architecture objectives are:
I. Provide scalability.
II. Efficient development process (independent deployment and no application restart required).
III. Better production support (no application restart required for changes).
More on the architecture:
a). Functional scalability, meaning this that my application may functionally grow up to an indeterminate number of small functional modules.
b). Modules will be developed, deployed and maintained independently so the application discovers and loads classes on demand.
c). Avoid a big .war file containing all the small modules because a small change in one module would involves deploying all the other modules (possibly hundreds o even thousands of them) and restarting the application.
d). Above point involves dynamic class reloading.
I guess this is addressed by OSGI (looks like heavy to deal with), Jigsaw (still under development) and maybe others. I think the key point is the class loader. I will develop a custom class loader but maybe you have some advice for me before starting to develop.
Thanks and regards.

Answer 1

Classes maintained by the container should not be loaded by an application. You want the container to read those classes and react accordingly. Most of those classes are read when the container starts up a container restart will be required. Trying to leverage another container within a container does not sound like it will be worth (if you can get it to work).
Perhaps you should state the problem that you are trying to solve with these modules so that others may suggest more feasible solutions to achieve your target goals.