JSP/Servlet design question - Make request/response globally available via JNDI

Question

In PHP one is always able to access the current request or response from any part of their code. This concept is fundamental to PHP programming. Request data, response data, session data (etc) are always there!

This does not happen in Java Servlets! In order to have access to the HttpServletRequest, HttpServletResponse, HttpSession (etc) in your code you need to pass them around as function variables. This means that you cannot code a web framework that inherently "knows" about all these and removes the complexity of passing them around.

So, I have devised this solution:

1. Create anf register a ServletRequestListener.
2. Upon the requestInitialized event bind the current HttpServletRequest to the JNI context giving in the name of the current Thread (Thread.currentThread().getName());
3. Upon the requestDestroyed event unbind the above JNI resource to cleanup.

This way one has access to the current request/response from any place of their code, since they are always there in the JNI context and can be retrieved by providing the current thread's name.

All known servlet container implement the single-thread model for each request, so there is no way for the requests to get mixed up (of course one must not forget to clean them up).

Also the JNI resources of each web application are separated by default so there are no concerns of mixing them up or of security issues that could arise from one web application having access to the requests of the others.

Kinda twisted, but nice and simple...

What do you think?

Answer 1

I think some web frameworks (GWT, Axis) already do that, but in a much simpler way: by using a ThreadLocal static variable (or accessible from a singleton). Spring also has this possibility.

I'm not sure it works with all the containers, though. If the container uses non-blocking IO and reuses the same thread to handle multiple requests in parallel, it won't work anymore.

See Get the HttpServletRequest (request) object from Java code for a similar question (and its answers).

Answer 2

If you are worried about different requests getting messed up (and then think about "sub requests" like a model window), perhaps you'd rather think about using Seam? They use an abstraction called a "Session" to handle a LOT of the things that we developers try to hack around with other traditional web technology stacks. Seam is built on JSF just as an fyi. You don't have to use EJB 3 or Hibernate with it, but it does integrate nicely with both of those as well. Something to think about.