Re: Deprecation in data model

Very intersting, thanks.

I'm trying my own root data model with an extends
freemarker.template.SimpleHash, and with a redefinition of get(String
key) method, With that I can see the calls to the terms in root model,
youpiii! It's a great new year!

Two questions :

- you say a custom class is required only if return value is a hash,
for the redefined get method in TemplateModel. But how I know if it's
a hash ? Il see than TemplatehashModel don't inherit from
java.util.Map.

- in a custom ObjectWrapper.wrap, how I know the template name of this object ?


Great year.



2009/12/31 Daniel Dekany <[email protected]>:
> Thursday, December 31, 2009, 1:49:53 PM, Ista Pouss wrote:
>
>> 2009/12/31 Daniel Dekany <[email protected]>:
>>> Wednesday, December 30, 2009, 3:57:36 PM, Ista Pouss wrote:
>>>
>>> As far as FreeMarker is concerned, yes, but it's always a question if
>>> the framework your are using gives sufficiently low-level access to
>>> FreeMarker... Anyway, if it does, since "term" is a top-level data,
>>> you could use a custom TemplateHashModel implementation that does
>>> this. (If are using a java.util.Map as the data-model root, you could
>>> wrap it into your TemplateHashModel implementation just before passing
>>> to the template.process call)
>>>
>>
>> Yes my root data model is a Map, so You say I do something like
>>
>> template.process(new CustomTemplateHashModel(map), output);
>>
>> and, in my Custom...
>>
>> TemplateModel get(String key)
>> {
>>  if (deprecated(key))
>>    System.out.println("Damned! Deprecated!");
>>  return super.get(key);
>> }
>>
>> Is it OK ?
>
> Yes, something like that.
>
>> But what's append if the deprecated term is, from root, thing in
>> "foo.bar.thing" ?
>
> The basic idea is that the TemplateModel that you return with
> get(String) must also be of a custom class so that it will be aware of
> the name (path) of its parent and also of the whole deprecation
> checking thing. More precisely, using a custom class for the return
> value is only required if (a) the returned value itself is a hash (so
> it can create further TemplateModel-s; you want to monitor that) (b)
> you are still on a path that can lead to a deprecated object.
>
> As of the implementation... I would write a custom ObjectWrapper by
> extending BeansWrapper or DefaultObjectWrapper (whichever you plan to
> use). Then I would configure FreeMarker to use that wrapper
> (Configuration.setObjectWrapper or the "object_wrapper" property).
>
> What should the custom implementation do? I would override the
> wrap(Object) method, which would just call super.wrap, except if the
> object to wrap is an instance of com.yourcompany.MapWithDeprecations,
> in which case it would wrap it with
> com.yourcompany.DeprecationAwareTemplateHashModel.
> DeprecationAwareTemplateHashModel would be the extension of the class
> that the ObjectWrapper you extended normally uses for maps (so if
> those have any fancy extra features, yours will have them too).
>
> MapWithDeprecations would be something that extends HashMap class. You
> would instantiate it somehow like "new MapWithDeprecations(dataModel,
> deprecations)", and that's what you pass to Template.process. So I
> simply made the deprecations the part of the data-model, and made the
> ObjectWrapper be aware of that information. If somewhere you just pass
> in a plain HashMap as the data-model, it will still work, only without
> the deprecation warnings. (Or if you pass in a MapWithDeprecations,
> but you are using a standard ObjectWrapper, it will still work, just
> again without deprecation warnings. Robust...)
>
>> Thanks.
>
> --
> Best regards,
>  Daniel Dekany
>
>
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