@RequiresSession
  public Set<HostConfigMapping> findSelected(final long clusterId, Long hostId) {
    populateCache();
    
    if (!hostConfigMappingByHost.containsKey(hostId))
      return Collections.emptySet();
    
    Set<HostConfigMapping> set = new HashSet<>(hostConfigMappingByHost.get(hostId));
    
    CollectionUtils.filter(set, new Predicate() {
      
      @Override
      public boolean evaluate(Object arg0) {
        return ((HostConfigMapping) arg0).getClusterId().equals(clusterId) 
            && ((HostConfigMapping) arg0).getSelected() > 0;
      }
    });
    
    return set;
  }
Used for host configuration mapping operations.
ambari-server/src/main/java/org/apache/ambari/server/orm/dao/HostConfigMappingDAO.java