Hi, I was asked to create this issue after exchanging some emails in the struts mailing list.
I had the following problem:
I am having problems populating an action variable Set by request using
struts type conversion if the Set has the element type defined as an
I have a UserAction-conversion.properties file with the following
configuration using the class implementation:
And UserAction has the collection Set<RolesInterface>. Roles obviously
If the Set element type <RolesInterface> is deleted it works just fine.
Am I doing something wrong or is this not possible?
And this was the response, which fixed my problem. :
I reproduced it and seems it's because it tries to instantiate a new
element but the interface cannot being instantiated. Please see  to
know why it tries to instantiate interface instead of class.
Annotating the getRoles or setRoles method with @Element(value =
path.to.class.Roles.class) may fix this issue. (shouldn't it be
path.to.class.Role instead? it seems Roles is a list not element)
After acknowledging the issue is fixed, the fix suggestion:
You're welcome :) glad to hear this. However, I think it's better that
Struts honor .properties file (where element class has been defined
strictly by user) before the generic parametrics . Could you please
register an issue at  with title "conversion fails when generic type
is an interface" then paste these emails contents in it's description.
Thanks for your report!