Can't I use subfolders in WEB-INF/lib?

Question

I'm doing some clean-ups in a GWT (no maven) project. It has a lot of jars added in WEB-INF/lib. I know the purpose of those jars (for example for REST service - luckily it's documented) so I wanted to put them in appropriate subfolders for nicer look.

After re-adding them to build path (as now they are in subfolders) I tried to run SuperDevMode and got multiple warnings:

Server class 'X' could not be found in the web app, but was found on the system classpath

and some errors like:

Cannot find a default implementation of the HK2 ServiceLocatorGenerator

When I put those jars back in WEB-INF/lib (without subfolders) and re-add to build path everything runs just fine.

My question is: can't/should't I use subfolders in WEB-INF/lib? If so, why?

Answer 1

Server class loader is programmed to look only into WEB-INF/lib, not other folder nor subfolders.

I strongly suggest to get into the maven world, it has a steep learning curve but it will assure to your project a solid foundation to grow on. Another big plus of Maven is that it can automatically pick up the latest security patch of your libraries (Equifax, anyone?).

Extract from the Apache Tomcat 7 Docs:

WebappX — A class loader is created for each web application that is deployed in a single Tomcat instance. All unpacked classes and resources in the /WEB-INF/classes directory of your web application, plus classes and resources in JAR files under the /WEB-INF/lib directory of your web application, are made visible to this web application, but not to other ones.

Answer 2

Server class loader is programmed to look only into WEB-INF/lib, not other folder nor subfolders.

I strongly suggest to get into the maven world, it has a steep learning curve but it will assure to your project a solid foundation to grow on. Another big plus of Maven is that it can automatically pick up the latest security patch of your libraries (Equifax, anyone?).

Extract from the Apache Tomcat 7 Docs:

WebappX — A class loader is created for each web application that is deployed in a single Tomcat instance. All unpacked classes and resources in the /WEB-INF/classes directory of your web application, plus classes and resources in JAR files under the /WEB-INF/lib directory of your web application, are made visible to this web application, but not to other ones.