insert textfield value into a collection in struts2 - struts2

Question

I have this bean class
Class Address {
private String addressId;
private Set<Location> setOfLocations;
// more attributes
//getters and setters
}
Class Location{
private Long locationId;
private String locationName
private String nearestHospital;
//getters and setters
}
in the jsp I have a textField controls for the Address class members, and also for Location class members one for locationName and nearestHospital.
the Address class members map normally because the model driven interface map them to their respective fields. the problem is how i can map the location textFields to a location object inside Set member of the Address class

Answer 1

Add new item to collection
Using type conversion and a list instead of a set, this will work to add a new item to the list:
<s:textfield name="locations[%{locations.size()}].locationName"/>
If you want to use a set, then I don't know how to achieve what you want without spending some time digging, but you will want to start here.
Display and edit existing collection items
On the other hand, if you were to want to be able to display and edit an existing collection, then this should work if you use a list instead of a collection:
<s:iterator var="listItem" value="yourList" status="listStatus">
<s:set name="paramName">yourList[${ listStatus.index }].someField</s:set>
<s:textfield name="%{#paramName}" value="%{#listItem.someField}"/>
</s:iterator>
Here, your model would have a list called yourList. The items in yourList contain a field called someField. We are able to set the value onto the fields by setting the request parameter name to be in the form yourList[2].someField so that OGNL will evaluate this and set the parameter value onto the someField field of item 2 of yourList.
Using your classes as you show them above but with changing the locations to a list, we would have:
<s:iterator var="location" value="listOfLocations" status="locationStatus">
<s:set name="paramName">listOfLocations[${ locationStatus.index }]</s:set>
<s:hidden name="%{#paramName}.locationId" value="%{#location.locationId}"/>
<s:textfield name="%{#paramName}.locationName" value="%{#location.locationName}"/>
<s:textfield name="%{#paramName}.nearestHospital" value="%{#location.nearestHospital}"/>
</s:iterator>
Or, if you are using JSTL, this will do the same:
<c:forEach var="location" items="${ listOfLocations }" varStatus="locationStatus">
<s:set name="paramName">listOfLocations[${ locationStatus.index }]</s:set>
<s:hidden name="%{#paramName}.locationId" value="%{#location.locationId}"/>
<s:textfield name="%{#paramName}.locationName" value="%{#location.locationName}"/>
<s:textfield name="%{#paramName}.nearestHospital" value="%{#location.nearestHospital}"/>
</c:forEach>