Hi Keith.
I look at the system as having several complementary models, controllers and event triggers. Struts Action, ActionForm, and submit triggers are among them but not the only ones. In other words, I don't see Struts Actions as being the only system entities that can respond to event triggers, and ActionForm beans are not the only data containers. As you have discovered, the struts objects are really only good at responding to a subset of the possible events, and handling a subset of the pages data. I think that is intentional rather than a flaw. If you buy that, then you can use "page load" as an event trigger, and your own home grown "NewsModel" bean. Some other home grown controller can go get the data and push it into the news bean. These homegrowns cause you trouble when you try to force them to be children of Action and ActionForm. So I'm suggesting only that the tag load and display the data from the news model. However, if you wish to have the "page load event" trigger a model update, the lines get a bit blurry because I'm using the custom tag's execution thread to kick off the model load, and refresh the display. Although that thread is involved with "double duty" the object model is still clean --- the custom tag is just rendering data, and some other controller logic is getting the data. You could use other events to load the news bean such as user log in, periodic polling, etc. Not sure what your requirements are here but I'm guessing you want the news updated on each page load. OK I'll shut up with the philosophical stuff and let you get back to the real solution that Matt helped you with :) Good Luck /Ross -----Original Message----- From: Keith Chew [mailto:[EMAIL PROTECTED]] Sent: Wednesday, March 06, 2002 6:02 PM To: Struts Users Mailing List Subject: RE: design flaw if using a template... Hi Ross Good comments. You see, with custom tags, there are several problems: - For each different parts of the template, I need to create a custom tag - This custom tag is actually what an xxxAction class is meant to do, ie retrieve data from a database and prepare the data for view - If I later decide not to put news in the template and put it in a separete page, I need to port the taglib code to an xxxAction class. Not very flexible. - taglibs from Struts point of view, only renders data for viewing. It should not be performing model work, which should really be in the xxxAction class. So, I can see that Struts was designed to handle "user invoked" actions, not "code invoked" actions. Any more thoughts? Keith -----Original Message----- From: Ross MacCharles [mailto:[EMAIL PROTECTED]] Sent: Thursday, 7 March 2002 11:14 a.m. To: 'Struts Users Mailing List' Subject: RE: design flaw if using a template... Consider rethinking the philosophy that all data rendered in the JSP must come from an ActionForm. In my mind the ActionForm generally represents the editable data for the page displayed to the user. There's no problem with displaying data from other sources on the same page - especially read only data. For news I would simply use a custom tag to get it and display it. Put another way, I wouldn't want to have to set up a bean with "setNews" and "setMemberCount" when I have no intention of allowing my application to edit those values. /Ross -----Original Message----- From: Keith Chew [mailto:[EMAIL PROTECTED]] Sent: Wednesday, March 06, 2002 4:28 PM To: Struts Users Mailing List Subject: design flaw if using a template... Hi Struts provides us with a nice MVC architecture, where: - a user's click maps to an Action - based on the results, the user is forwarded to the view Now, I have a template.jsp which all pages will use. The template will contain some views that are common to all pages, eg: - Latest News - Site visits - Member count To retrieve these information, it gets them from the database. However, there is no user click to invoke the action. This is where the limitation of Struts comes in. Let me explain: In the template.jsp, we can have: <template:insert template="news.jsp"/> In news.jsp we can access the database and retrieve the news for display. This breaks the MVC pattern, since the view is accessing the model. Alternatively, we have have this in the template.jsp: <template:insert template="news.do"/> This will call the NewsAction which accesses the database, and forwards the results to the news.jsp for display. This is a great concept, but it does not work. Struts does not allow multiple forwards (this happens when the current page is already a .do). Here's an example: (1) User clicks on viewUserDetail.do (2) ViewDetialAction forwards to user.jsp (3) In template.jsp (used by user.jsp), news.do invokes NewsAction, and it forwards to news.jsp This is a double forward, which results in an exception. Basically, I want to call <template:insert template="news.do"/> in the JSP. Has anyone done something like this? Keith -- To unsubscribe, e-mail: <mailto:[EMAIL PROTECTED]> For additional commands, e-mail: <mailto:[EMAIL PROTECTED]> -- To unsubscribe, e-mail: <mailto:[EMAIL PROTECTED]> For additional commands, e-mail: <mailto:[EMAIL PROTECTED]> -- To unsubscribe, e-mail: <mailto:[EMAIL PROTECTED]> For additional commands, e-mail: <mailto:[EMAIL PROTECTED]> -- To unsubscribe, e-mail: <mailto:[EMAIL PROTECTED]> For additional commands, e-mail: <mailto:[EMAIL PROTECTED]>
