<s:text name="myobj.mymap['foo']" value="bar" />
Clearing the value from input box rendered by above drops the key-value instead of setting key's value to null.
There have been discussions before () and final word was that key's value should be set to null. But still, mapped property is ignored if value is empty.
Workarounds include having an extra "mymap" on the action bean and on save copy that to the in-place "myobj.mymap", or on pre-binding based on event clear the maps, but those takes some of the intuitivity away from the framework.
Note that the following works without problems;
<s:text name="myobj.myobjmap['foo'].attr" value="bar" />