AssigneeService Service that retrieves issue-assignable ApplicationUser objects. 
UserPickerSearchService This interface is deprecated. Use UserSearchService instead. Since v7.0.  
UserSearchService Service that retrieves a collection of ApplicationUser objects based on a partial query string 


DefaultAssigneeService The main implementation of AssigneeService
IteratedSearcher Iteratively queries an underlying data source that supports query offset and limit to perform a search with a client-side filter. 
UserMatcherPredicate Matcher to compare User parts (username, Full Name and email) with a query string and return true any part matches. 
UserSearchParams Optional parameters to restrict a user search. 
UserSearchUtilities Provide a centralised location for accessing functions and other utilities that help to produce the queries needed to perform user searches in both Crowd and in-memory Java