我应该如何决定用@async注解哪些rest方法，以及为什么我们需要用@async注解某些方法？
例如

@RestController
public class controller {

    private  employeeservice eserv;

    @GetMapping(value = "/emp")
    public List<Employee> getEmployees()
    {
        return this.eserv.getEmployees();
    }

    @PostMapping(value="/emp")
    public Employee addemployee(@RequestBody Employee emp)
    {
        return this.eserv.addemployee(emp);
    }
}

这是服务类示例

@Service
public class employeeserviceimpl implements employeeservice {

    @Override
    public List<Employee> getEmployees(){
        return list;
    }

    @Override
    public Employee addemployee(Employee emp) {
        list.add(emp);
        return emp;
    }
}