Tapestry 5：持久性页面数据的初始化

Question

Consider following scenario. Have a page with some persistent object obj :

public class SomePage {
   @Persistent
   @Property
   SomeBean obj;

   @Property
   @PageActivationContext
   private SomeActivation actObj;

   ...

   void onValidateFromForm() { ... }
}

This obj is edited on a page:

<t:textfield t:id="value" t:value="obj.value"/>

Lets consider initialization procedure of obj state like this:

(*) obj.value = actObj.value;

(I strongly need to unbind value from actObj , please don't ask why).

Have also a validation method. When validation fails, I'd like to show errors list on page and keep also all values, which user filled on form and which were stored into obj .

So:

1. when page firstly initialized with specific actObj I'd like to initialize obj
2. when page validation fails, I don't want to reinitialize obj , because I want to keep its values and show them user with errors list.

The question is: where I should place initialization block (*) ?

Answer 1

You should be able to use onActivate() as this will occur before the request parameters are applied. So your submit event will first set the value from the activation context and then overwrite it with the value from the text field.

Note that tapestry only does a redirect after post when validation succeeds. When validation fails tapestry renders the errors in the POST response. For this reason, you might find that you don't need @Persist at all and can go stateless via @PageActivationContext / onActivate() / onPassivate()

Answer 2

You can use activation handler instead of annotation, so:

@Persistent
@Property
private SomeBean obj;

@Property
private SomeActivation actObj;

@OnEvent(EventConstants.ACTIVATE)
void activatePage(SomeActivation actObj) {
  this.actObj = actObj;
  if (obj == null) {
    obj = // initialize
    obj.value = actObj.value
  }
}

@OnEvent(EventConstants.PASSIVATE)
Object passivatePage() {
  return actObj;
}

@OnEvent(value = EventConstants.SUCCESS, component = "form")
void success() {
  // do some staff

  // reset obj
  obj = null;
}

@OnEvent(value = EventConstants.FAILURE, component = "form")
void failure() {
  // do some staff
}