@Service
public class SomeWorkflowService {

    @Autowired
    HistoryService historyService;

    @Autowired
    TaskService taskService;

    public Map<String, Object> currentTaskService(String currentTaskId) {
        Map<String, Object> taskMap = new HashMap<>();
        Task currentTask = taskService.createTaskQuery().taskId(currentTaskId).singleResult();
        HistoricTaskInstance previousTask = findPreviousTask(currentTask.getProcessInstanceId());

        taskMap.put("Current task name: ", currentTask.getName());
        taskMap.put("Previous task name: ", previousTask.getName());

        return taskMap;
    }

    // Order tasks by end date and get the latest
    public HistoricTaskInstance findPreviousTask(String processInstanceId) {
        return historyService.createHistoricTaskInstanceQuery().
                processInstanceId(processInstanceId).orderByHistoricTaskInstanceEndTime().desc().list().get(0);
    }

}