Get the users inside issue security level through a plugin

Hi everyone,

I am developping an external application connecting to Jira (both Server and Cloud) using the Rest API.
My goal is to get the users inside issue security levels. In the API, you can get the issue security scheme and their respectives levels but you cannot get more informations about the users inside those levels.

As my application needs to keep the security / accessibility aspect from inside Jira, its only the missing key to finish my work.

To do so, I want to list all users as ApplicationUser and then using the IssueSecurityLevelManager, get the levels they are member of.

I’m currently creating a REST plugin2 for Jira and another thread gave a solution to list all the users.

The problem is I cannot use UserSearchService.findUsersAllowEmptyQuery() as it is an interface and I don’t have the DefaultUserPickerSearchService in my packages I downloaded for my project.
My version of jira is 7.2.2

Thanks for the help