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.
--
This message is automatically generated by JIRA.
-
If you think it was sent incorrectly contact one of the administrators:
http://www.stripesframework.org/jira/secure/Administrators.jspa
-
For more information on JIRA, see: http://www.atlassian.com/software/jira
------------------------------------------------------------------------------
This SF.net email is sponsored by:
SourcForge Community
SourceForge wants to tell your story.
http://p.sf.net/sfu/sf-spreadtheword
_______________________________________________
Stripes-development mailing list
[email protected]
https://lists.sourceforge.net/lists/listinfo/stripes-development
