how to use different entity manager for different data source

I want to execute the same query on different database based on the request mapping url in controller .

Below is code snippet from my service impl class.

@Service("metricsService")
public class MetricsServiceImpl implements MetricsService {
    
    @PersistenceContext
    private EntityManager entityManager;
    
   String sql_query = "Select count(*) from user_details";

    public int countWPReqRaisedWithinDateRange(Date fromDate,Date toDate) {
        Query query = entityManager.createNativeQuery(sql_query);
        query.setParameter("fromDate", fromDate);
        query.setParameter("toDate",toDate);
        int count = ((Number) query.getSingleResult()).intValue();
        return count;
    }

}

I want to execute the same sql_query on different database based on the request mapping url.How can i customise this injected entity manager to execute on different database??