Re: [Springframework-developer] Spring binding and validation for Struts

[Keith D. <ke...@in...>]

Awesome, Juergen, glad to see this cleanup here as I was always in to what
that code was doing (allowing us to use Spring's data binding with Struts)
but never really happy with the implementation.  Nice work.

I think the autowire option is important enough to keep in.  It really is
the simplest way to get DI on your actions.

Keith

> I've now also given a Juergen treatment ;-) to the Spring
> binding/validation
> adapter for Struts that Keith committed to the main source tree.
>
> For everybody not familiar with this from the Web Flow side of things: The
> idea here is to allow for using Spring's DataBinder/Errors mechanism
> within
> a Struts web tier, seamlessly exposing the result to traditional Struts
> views (with "html:form", "html:errors", etc).
>
> I've significantly reworked this: In contrast to its original inception
> where there've been a special RequestProcessor, a special PlugIn and a
> special ActionForm, what's left now is - a single SpringBindingActionForm
> adapter. SpringBindingActionForm cares for everything necessary: from
> extending Commons BeanUtils to exposing the Spring-managed errors as
> Struts
> ActionMessages.
>
> There is no special RequestProcessor necessary anymore, which I consider
> as
> a must: Too many Struts extensions subclass the RequestProcessor
> themselves,
> including Tiles and our own Delegating Action mechanism.
>
> The final usage style looks as follows. In "struts-config.xml", a single
> ActionForm is defined for all Actions:
>
> <form-beans>
>   <form-bean name="actionForm"
> type="org.springframework.web.struts.SpringBindingActionForm"/>
> </form-beans>
>
> In each Struts Action that wants to use Spring binding/validation for a
> plain POJO form object, the following pattern can be used:
>
> public ActionForward execute(ActionMapping actionMapping, ActionForm
> actionForm, HttpServletRequest request, HttpServletResponse response)
> throws
> Exception {
>   SpringBindingActionForm form = (SpringBindingActionForm) actionForm;
>   MyPojoBean bean = ...;
>   ServletRequestDataBinder binder = new ServletRequestDataBinder(bean,
> "myPojo");
>   binder.bind(request);
>   form.expose(binder.getErrors(), request);
>   return actionMapping.findForward("success");
> }
>
> Keith/Erwin, please give this reworked version a try in Web Flow's Struts
> adapter. As far as I can see, it should still work nicely for those needs.
>
> ---
>
> Regarding the further Struts support classes added alongside the
> binding/validation support:
>
> The TemplateAction class essentially duplicated what our existing
> ActionSupport already did, plus a view convenience mirrors of static
> utility
> methods (which I consider unnecessary - why not access the corresponding
> static RequestUtils methods directly). The "preExecute" and "postExecute"
> are fine in general, but it's not Spring's business to provide such Struts
> stuff that's not related to Spring mechanisms... Hence, I've dropped
> TemplateAction completely.
>
> DependencyInjectedAction, which autowires the Action instance by type, is
> not a bad idea. I don't think that it should be a dedicated class, though,
> so I've removed it as well. If we intend to recommend such an autowiring
> pattern for Struts Actions, we should build it as an option into the
> existing ActionSupport class. However, there's DispatchActionSupport and
> Lookup/MappingDispatchActionSupport as well, so we'd need to duplicate
> quite
> a bit...
>
> Note that we also offer a Delegating Action mechanism, which completely
> defines Struts Actions in a Spring context. Of course, any kind of
> autowiring is available to those instances already. Hence, I'm not sure
> whether we should provide yet another dependency injection for Struts
> Actions out-of-the-box. If we consider this important enough, I won't
> mind,
> but we should strive for integrating this into the existing
> XxxActionSupport
> classes - if at all.
>
> Juergen
>
>
>
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-- 
Keith Donald
Principal Consultant, Interface21
http://www.springframework.com - Spring Services From the Source