What are all the portlet classes in Spring mvc?

Question

In Spring MVC there seem to be two parallel class hierarchies, one with portlet, one without.

What is that? Why is it so and what should I use.

Answer 1

That's because

In addition to supporting conventional (servlet-based) Web development, Spring also supports JSR-168 Portlet development. As much as possible, the Portlet MVC framework is a mirror image of the Web MVC framework, and also uses the same underlying view abstractions and integration technology.

The Spring documentation (Chapter 16. Portlet MVC Framework) provides more information about the differences.

To answer your last question: you should use the Portlet MVC framework if you are developing portlets (web applications to be deployed in a portal). If you are developing conventional web applications you should use the Web MVC framework.