Once I found it difficult too, and I never used EventContext because I think it is not better than multiple onActivate.
Finally I wrote my own PageActivationContext called PageActivationUnit, the difference is that PageActivationContext only can occur once, but PageActivationUnit can be used in multiple fields. For example, a product search page, it has params like category,keyword,pagesize,pageno,brand and so on. If using PageActivationUnit, the java would be like: @PageActivationUnit private Category category; @PageActivationUnit private String keyword; @PageActivationUnit private Integer pagesize; @PageActivationUnit private Integer pageNo; @PageActivationUnit private Brand brand; PageActivationUnit will handle all the activate and passivate event for me, and the url requested would be like '/searchpage/category-value/keyword-value/pagesize-10/pageNo-2/brand-value'. Yes, I encode the field name in the url and its value in a pair. Another advantage is if later another param 'orderBy' is added, I don't have to change any code at all. DH http://www.gaonline.com.cn ----- Original Message ----- From: "Kalle Korhonen" To: "Tapestry users" <users@tapestry.apache.org> Sent: Tuesday, December 08, 2009 2:22 PM Subject: Best practice for initializing page to default context > Most things in T5 are delightfully simple, but I find this > surprisingly difficult: how to best initialize a page to default > context (and redirect to it). Imagine you have a search & result page. > If I access the page without any context I want all records to be > displayed. In onActivate() without parameters I set the context to > *all* and return this to redirect, then I query the database in > setupRender() to initialize the data for the grid. However, sorting > the grid will also cause a call to onActivate() without parameters, > resetting my data to the default context. The parameter-less call to > onActivate() would be harmless if I didn't do a redirect from > onActivate() but then I cannot set the default context and redirect. > In setupRender() I could decide whether redirect is needed or not but > at that time, I'm already committed to rendering the request. > > Because events cause a parameterless onActivate() call, I tend to > reserve onActivate() for possible component/event initialization needs > only and always link to pages with initial context already set. I also > find it roughly impossible to use overloaded versions of onActivate() > and subsequently, if my page has multiple entry points, I typically > resort to implementing it in a single onActivate(EventContext > eventContext) operation containing a big if-else clause. Since the > activation context is anyway sent with an event request (as in > ?t:ac=mycontext), rather than using the encoded context for rendering, > wouldn't it be just simpler if that context was used for activating > the page for the event request and the following redirect for > rendering would just use whatever context onPassivate() returns? What > do others think, how do you handle this? > > Kalle > > --------------------------------------------------------------------- > To unsubscribe, e-mail: users-unsubscr...@tapestry.apache.org > For additional commands, e-mail: users-h...@tapestry.apache.org > >
