How to access a collection of SseEmitters located inside a #Service Class - spring

Question

The sses Map has been moved from MessageController class to a class annotated with #Service MessageTemplate.class . Now we need a way to add SseEmitter instances (created inside openConn()) to the sses map inside MessageTemplate class.
Map may not be the best choice here, if so, what other cache alternatives available because I need a away to send messages back to individual clients?
#Controller
#RequestMapping(value="/")
public class MessageController{
#Autowired MessageOperations mesgOps;
//Moved to MessageTemplate
Map<String, SseEmitter> sses = new ConcurrentHashMap<>();
#GetMapping(value = "/conn/{username}")
public SseEmitter openConn(#PathVariable("username") String username){
SseEmitter sseEmitter = new SseEmitter(3600000L);
sses.put(username, sseEmitter);
return sseEmitter;
}
#Service
public class MessageTemplate implements MessageOperations{
//The above map now resides here.
Map<String, SseEmitter> sses = new ConcurrentHashMap<>();
..
}

Answer 1

Assuming, all the presented abstraction in the question are “custom” (the code that was written in your organization) and do not belong to spring ecosystem by themselves, I see the following:
A MessageTemplate is a singleton-scoped bean driven by spring
The controller is also a singleton bean.
MessageOperations interface is your custom interface that you’re using for injection.
In this case the obvious change would be:
interface MessageOperations {
SseEmitter associateSseEmitterWithUser(String userName);
}
#Service
public class MessageTemplate implements MessageOperations {
private Map<String, SseEmitter> sses = new ConcurrentHashMap<>();
// other existing code you might already have
public SseEmitter associateSseEmitterWithUser(String username) {
SseEmitter sseEmitter = new SseEmitter(3600000L);
sses.put(username, sseEmitter);
return sseEmitter;
}
}
#Controller
#RequestMapping(value = “/“)
public class MessageController {
#Autowired MessageOperations mesgOps;
#GetMapping(value=“/conn/{username})
public SseEmitter openConn(#PathVariable(“username”) String username) {
return mesgOps.associateSseEmitterWithUser(username);
}
}