Thank you Christopher, but Peter made the same (ThreadLocal) proporsal a bit earlier in the thread. However, as for the other point concerning interface change, I'm not looking for a quick solution but rather redesign our current architecture. The 'hidden' parameter transfer may be not a best practice, but it has some great advantages. For example, if I need the current user's country somewhere deep in the BL I could change all interfaces inbetween and add the country (or locale) parameter, but than I have one of nine methods having this parameter. If I am consequent, I'd have to add standard parameters like current userId, locale, etc to each method in each interface which wouldn't make method signatures better readable. Consider: public void sendMessage(Message message) against public void sendMessage(Message message, UserId currentUserId, SessionId currentSessionId, Locale currentLocale.....) which one is better to understand?
Using a hidden CallContext is like using the request/session in the webapp or using interceptors/piggybaging in middleware. Since we are talking about must-have (but not must use) parameters in each call, I think the advantages are greater than the drawbacks. regards Leon On 7/21/06, Christopher Schultz <[EMAIL PROTECTED]> wrote:
Leon, > As far as I see I have two opportunuties: > 1. To alter all interfaces in all layers and add a CallContext > parameter which would contain additional information gathered in the > top level and evaluated on demand > or 2. Have this CallContext object in somewhere in the VM, where I can > access it from everywhere in the application without to actually > change interfaces. The only location for the second case is imho the > current Thread. As much as I cringe bringing this up, there is another possibility: use a ThreadLocal. You can basically use the Thread as a storage device, which sort of fits into your solution #2. The advantage is that you do not have to subvert the existing thread management strategy in Tomcat. > Now I have the unpleasant > situation that i need some information pretty deep in some use cases > of the application (like current locale) which I only have at the top > (servlet) level. I think that if you really need this information deep in your code, then you simply should modify your interfaces, etc. I realize that you probably want to get this solved as quickly as possible, but if you start coming up with unusual ways of getting data from one part of the call chain to another, then people who have to work on your code are going to get confused and angry. If you decide to do something crazy, make sure you document it fully, including the reasons why you didn't use standard method parameters to achieve the same end. -chris
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