Mybatis中的游标查询Cursor(滚动查询)

// 策略为向下滚动    
    @Options(resultSetType = ResultSetType.FORWARD_ONLY)
    @Select({"select * from task where status!=#{status} order by create_time desc"})
    Cursor<Task> getTasksStatistic(Integer status);

// TaskCursorVo是封装类
TaskCursorVo getTaskStatus(Integer currentIndex, Integer pageSize);

public TaskCursorVo getTaskStatus(Integer currentIndex,Integer pageSize) {
        TaskCursorVo taskCursorVo=new TaskCursorVo();
        List<TaskStatusVo> collect=new ArrayList<>();
// 第一个参数为方法名，第二个参数是查询条件的值（如果没有查询条件就写null），第三个条件是从下标为currentIndex的开始查pageSize条数据
        Cursor<Task> tasksStatistic = sqlSessionTemplate.selectCursor("getTasksStatistic",DELETED.getCode(),new RowBounds(currentIndex,pageSize));
// 对结果进行遍历封装
        Iterator<Task> iterator = tasksStatistic.iterator();
        while (iterator.hasNext()) {
                Task task = iterator.next();
                TaskStatusVo taskStatusVo = new TaskStatusVo();
                BeanUtils.copyProperties(task, taskStatusVo);
                taskStatusVo.setStatusName(Objects.requireNonNull(getByCode(task.getStatus())).getDesc());
                collect.add(taskStatusVo);
        }
        taskCursorVo.setTaskStatusVos(collect);
// 需要把当前下标返回给前端
        taskCursorVo.setCurrentIndex(tasksStatistic.getCurrentIndex());
        Example e=new Example(Task.class);
        Example.Criteria c = e.createCriteria().andNotEqualTo("status", DELETED.getCode());
        List<Task> tasks = taskMapper.selectByExample(e);
// 把总条数查出来给前端
        taskCursorVo.setTotalSize(tasks.size());
        return taskCursorVo;
    }

@GetMapping("/taskStatus")
    public ResultModel taskStatus(@RequestParam(defaultValue = "0") Integer currentIndex,@RequestParam(defaultValue = "20") Integer pageSize){
// 第一次默认从第0条开始查询20条，往后的前端会把上次请求返回的当前下表传过来
// 如果不是从第一次查询，就要从上次查询当前下标的下一条数据开始查询
        if (currentIndex!=0){
            currentIndex+=1;
        }
        TaskCursorVo taskCursorVo = taskService.getTaskStatus(currentIndex, pageSize);
        return ResultModel.success(taskCursorVo);
    }