Jeromy Evans
Fri, 25 Apr 2008 20:54:09 -0700
Eric D Nielsen wrote:
I've been investigating some interesting behavior regarding model-driven actions and found a past thread that covers the situation from late last year: http://www.nabble.com/ModelDriven-CRUD-validation-failure-still-causes-JPA-update-td12987242.html ... It would seem to be a way forward exists, however. Model Driven can be tweaked as follows: The model driven interceptor would need to a) capture the raw request parameters into some storage b) skip the second params interceptor c) create a copy of the getModel object (to ensure its detached from any persistence session -- need to make sure this works for other common persistence engines) d) run params/validation on this copy e) if no validation errors, run params on the orginal (still attached to the persistence session), and proceed as normal f) if validation errors, intercept calls to the getters for values in the raw request for redisplay -- need to worry about XSS issues here There's a lot of moving pieces, and I'm sure I'm missing some even more subtle interactions. However I do think something needs to be done. I'm interesting in tackling this, and am hoping for some feedback on the above outline of required changes.
Hi Eric,I haven't had an opportunity to absorb your suggestion properly yet but thought I'd mention I agree with your line of thinking that the validation mechanism in particular needs to be improved. However, this is a general problem that also applies to rich clients; that is responsibility for rolling back changes to a model, and various patterns have developed over the years. A temporary copy is a simple implementation, however within a JPA-environment automatically creating a clone is often infeasible or undesirable. For example, if it's attached to a session, this process may cause hydration of the entire object graph. Unless the framework is provided hints, it won't know what to safely/efficiently clone.
Having the framework maintain dirty flags or proxy for the model also seems ineffective as the JPA provider performs the exact same task, only better.
The option to write straight to the model (or DTO) and performing validation of the model (or DTO) is a distinguishing feature of Struts 2, but also the source of such complications. Anyway, I don't have a solution, but I do intend to start resolving the numerous validation issues in JIRA in the near future and this one is the list.
regards, Jeromy Evans . --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]