1. If you want to get current page path in OSGI Service class then pass request as an method argument to service class methods from model/servlet class & get page path using request present in the method parameter.
2. If you want to get current page path in servlet then you can get it using code shared by @Anudeep_Garnepudi.
You can not use Sling annotations in OSGI service. currentPage, currentNode etc.. are global sling objects which will be created while Sling resolving particular resource. As Sling model has all the capabilities of Sling, those variables/objects will be directly injected in to Sling Model in context of current request.
In OSGI service this is not that straight forward, you should get the current Page and then get path.
Get the ResourceResolver
Get current Resource
Adapt resourceResolver to PageManager
Get the current Page by passing current resource
Get path from Page
Try the below code snippet, might help. Here I am getting Resource and ResourceResolver from request.