JSF wrong display of elements when iterating a Map -

i have simplify problem as possible. basically, map not been printed correctly after make modifications on it.

i have following xhtml code:

<c:foreach items="#{personcontroller.groupedpersons}" var="persong">     <p>         <h:commandbutton action="#{personcontroller.removepersongroup(persong.key)}" type="submit" value="remove">             <f:ajax render="@form" />         </h:commandbutton>     </p>     <p>#{persong.key}</p>     <p>#{persong.value.size()}</p> </c:foreach> 

this iterates on map , prints information. each key, there button allows removing map.

with code in personcontroller bean (which @viewscoped , implements serializable):

private hashmap<integer, list<person>> groupedpersons;  public void removepersongroup(integer age) {     groupedpersons.remove(age); } 

my testing data has key=20 , 3 values (person) , key=30 , 1 value (person). first time load page , print map works fine.

• 1st test: press button 2nd group (key 30). removes group , prints map fine, remaining group. press button 1st group (key 20). removes group , prints map fine, empty.
• 2nd test: reload page. press button 1st group (key 20). traces shows removepersongroup() works fine , groupedpersons has single element of key=30. however, when ajax refreshes form, xhtml shows #{persong.key} = 20 (which has been removed) , #{persong.value.size()} = null (nothing shown, value empty). doing wrong? cannot find problem

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update

after doing 2nd test , having wrong deta displayed in xhtml, when refresh form button , refresh whole page, xhtml shows actual data correctly! there must (concurrency related?) making xhtml show wrong data.