ThreadLocal on Google App Engine (GAE)

I would like to make some request-wide data available in my app engine application.

Examples:

• The URL for which the request was made.
• Authentication information.

I see that ThreadLocal is on the whitelist: http://code.google.com/appengine/docs/java/jrewhitelist.html

Is ThreadLocal a good and safe way to make this information available? Are there alternative / better / more accepted ways?

From stackoverflow

• Yes, it is an accepted practice to store these things in a ThreadLocal. However, a more preferable approach is to pass these values around (as method arguments) wherever they are needed, instead of reaching for them. It's more preferable, because it's more testable at least.