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http://www.stripesframework.org/jira/browse/STS-638?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=11681#action_11681
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Mike McNally commented on STS-638:
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> Well, one simple approach would be to introduce a "@DontWorryAboutMe"
> annotation
I see now that that would be somewhat more complicated than it seems at first
blush. An annotation on the bean would work but that'd be a little coarse.
> DefaultActionBeanPropertyBinder incorrectly binds "null" to missing fields
> sometimes
> ------------------------------------------------------------------------------------
>
> Key: STS-638
> URL: http://www.stripesframework.org/jira/browse/STS-638
> Project: Stripes
> Issue Type: Bug
> Components: ActionBean Dispatching
> Affects Versions: Release 1.5
> Environment: All
> Reporter: Mike McNally
>
> The DefaultActionBeanPropertyBinder, in concert with the "form" tag, sports a
> feature designed to handle the problematic behavior of HTTP "checkbox" and
> (though I understand this one a little less) "select" elements. The form tag
> dumps out a hidden field with a value that comprises a list of the form
> parameters coded on the page. That list is used by the property binder code
> to detect that form field values coded into the actual form are missing from
> the HTTP request parameter map. When that happens, the property binder binds
> a null value into the action bean properties corresponding to each missing
> parameter.
> This behavior is probably useful sometimes, but the code that performs the
> binding does not do it carefully, and can in some cases incorrectly overwrite
> an already-bound non-null property value. Specifically, consider the case
> where an action bean has a bean-valued property called "thing", and the form
> contains three fields: "thing", "thing.x", and "thing.y". The "thing" field
> is a stripes:select tag whose options are name-id pairs of existing instances
> of the "thing" bean type. The "thing.x" and "thing.y" field are (say) simple
> stripes:text tags representing string properties of the "thing" bean type.
> Consider that the form may be intended to allow a user to select either an
> existing "thing" from the select tag, or to create a new thing with
> properties "x" and "y". To achieve that, the form will also have a pair of
> radio buttons set either to "new" - to allow "x" and "y" properties to be
> typed in for a new "thing" - or to "known", which enables the stripes:select
> element and disables "thing.x" and "thing.y". Thus, upon form submission,
> the HTTP request will contain either "thing.x" and "thing.y", OR it will
> contain only an id value for "thing", because client-side code will be
> careful to disable the form elements according to the radio button settings.
> In the former case - the case where the form submits a "thing.x" and a
> "thing.y" - what happens on the server is that the property binder will
> instantiate a "thing" for the action bean, and then set the values of
> "thing.x" and "thing.y" according to the HTTP parameters. It will then check
> the hidden "field manifest" form field and notice that "thing" is missing.
> It will therefore re-set the action bean "thing" property to null, thus
> overwriting the work already done.
> In the latter case - the case where the form submits a "thing" id value from
> the select tag and no values from "thing.x" and "thing.y" - the opposite, but
> equally bad, error will be carried out by the property binder. The action
> bean will be given the instantiated instance of "thing" based on the
> passed-in id value from the HTTP request. Then the code will notice that
> "thing.x" and "thing.y" are missing from the parameter map, so it will bind a
> "null" over the properties in the instantiated "thing" instance.
> I'm not sure how this should be fixed. There's no good workaround in the
> action bean, and I can't figure out a good workaround on the page. For now
> I'm going to create my own property binder class that just doesn't do that
> missing field check at all.
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