Although the change in Struts 1.1 to implement the RequestProcessor was a great improvement over having to extend the ActionServlet, as has been pointed out before, there can be issues when multiple people want to extend the RequestProcessor. For instance, my group extended the RequestProcessor so Struts would work well in our particular environment. Suppose we or our users want to utilize Tiles, which has some really great capabilities? Well, if we could extend the Tiles RequestProcessor we would now need another version of our RequestProcessor that extended the Tiles RequestProcessor rather than the base RequestProcessor. But in our case, we override doForward too (like Tiles does) and we would actually need Tiles to sit on top of (subclass) our RequestProcessor rather than the other way around. So we would have to take the Tiles source and generate another subclass of the TilesRequestProcessor that extended our RequestProcessor rather than the plain RequestProcessor.
And as more and more extensions become available, ideally we would like to be able to choose various combinations of extensions to use. Of course, using subclassing this becomes rather problematic for obvious reasons. If there are 3 different extensions you want to build upon, if you are lucky you could just create three different versions of your own RequestProcessor subclassing each of the those 3 separately. Of course, if you want to build on two at the same time..... Well, you get the idea. So, we, and we expect others, would like to improve the chances that our various extensions can be used together. We have implemented an approach based on the Decorator (Wrapper) pattern that allows processors to be chained together. If you choose not to subclass from this wrapper class things are the same. But if you make your RequestProcessor subclass from the wrapper and follow some simple steps, you can be part of an ordered chain of RequestProcessor instances. In addition to adding the wrapper, we had to make small changes to ActionServlet in getRequestProcessor (to build the chain the first time it is called) and the RequestProcessor itself to call the top (last) processor's methods and ControllerConfig to keep the chain of classes. Besides subclassing the wrapper class rather than the RequestProcessor, the only new things processors need to worry about is making sure to all the subclass version of the method they are extending and to call the top processors version's of other processor methods they call. For example, if you have your own processActionForward method you should remember to call super.processActionForward. You normally would want to do this anyway. Continuing the example if processActionForward wants to call doForward, it should call the top processors doForward instead because it might not be the top (last) processor in the chain. We know others have brought up the problem of multiple RequestProcessors before. We would be happy to donate our approach as a starting point, because we would like different extensions that require extensions to RequestProcessor to be usable together as much as possible without having to compile numerous different versions. For example, using the straight inheritance approach we would have to be prepared to generate a new version of the Tiles RequestProcessor extending our RequestProcessor every time there was a change made in the Tiles RequestProcessor. So maybe there are some far-reaching plans to address this issue in Struts or maybe someone else is already working on a different solution? If not, is there any interest in discussing extending the RequestProcessor support to support some kind of chaining approach? I would be happy to give more details on what we have come up with. I haven't submitted any patches yet, but I assume this is not the kind of thing one should simply submit as a patch anyway, at least not without discussing the appropriateness of the approach first. Thanks and sorry for the long post. Chris Seekamp -- To unsubscribe, e-mail: <mailto:[EMAIL PROTECTED]> For additional commands, e-mail: <mailto:[EMAIL PROTECTED]>
