This week's book giveaway is in the OO, Patterns, UML and Refactoring forum. We're giving away four copies of Refactoring for Software Design Smells: Managing Technical Debt and have Girish Suryanarayana, Ganesh Samarthyam & Tushar Sharma on-line! See this thread for details.
I think that the difference is on the classloader and methods that are used to find the resource. Classloaders have a hierarchy, that is, they form some kind of tree (where context classloader is the root of the tree) and resources (classes or properties files) loaded into memory by some classloader might no be visible to their parent. Also, they differ on where they search for the resource, for example, HttpServletRequest has a getResourceAsStream() method, that searches for resources under /WEB-INF either if webapp is "exploded" on the filesystem or packaged in a .war archive. Other getResourceAsStream() methods don't do that. You have to read documentation for specific behaviour of each method. Please, does anybody could confirm this ?