關於“導出”，數據量大，速度慢做的優化

@RequestMapping("/exportProduct")
public void exportProduct(ProductQueryDTO productQueryDTO,HttpServletRequest request, HttpServletResponse response) throws Exception{
    //只有管理員才能導出數據
    User user = LoginUtil.getUserInfo();
    Integer roleType = user.getRoleType();
    if(GlobalConstant.SEVEN != roleType){
        return;
    }
    Set<String> excludeColumnFiledNames = new HashSet<String>(ValidationUtil.getHashMapValue(16));
    multiThreadExcelExport.exportExcel("商品", response, productSkuMapper, productQueryDTO, ExportProductDTO.class,excludeColumnFiledNames);
}

/** service
 * 導出
 * @param name 導出名字
 * @param response  導出流
 * @param excelMapper 導出的頂級父類
 * @param base 查詢的頂級父類
 * @param head 導出的實體類
 * @throws Exception
 */
@SuppressWarnings("unchecked")
public void exportExcel(String name,HttpServletResponse response,ExcelMapper excelMapper, Base base,Class head, Set<String> excludeColumnFiledNames) throws Exception{
    String fileName = name+fastDateFormat.format(new Date());
    ExcelWriter writer = EasyExcel.write(getOutputStream(fileName,response),head).excludeColumnFiledNames(excludeColumnFiledNames).registerWriteHandler(myHorizontalCellStyleStrategy()).build();
    WriteSheet writeSheet = EasyExcel.writerSheet("Sheet1").registerWriteHandler(new EasyExcelColumnWidthConfig()).build();
    // 根據數據讀寫速度來調整，一般來說讀的邏輯復雜，比較慢，如果讀比寫快，這里設為1

　　// 查詢總條數
    Long count=excelMapper.excelListCount(base);
    Long total=count>50000?50000:count;
    // 分頁大小可以適當調整
    int pageSize = 5000;
    Long pageCount = total % pageSize == 0 ? (total / pageSize) : (total / pageSize + 1);
    int BlockingQueueSize=pageCount.intValue()==0?1:pageCount.intValue();
    // 大小設置為2就可以，作為緩沖
    BlockingQueue<List<T>> queue = new ArrayBlockingQueue<>(BlockingQueueSize);
    AtomicInteger start = new AtomicInteger(0);
    AtomicInteger writerCount = new AtomicInteger(0);
    ThreadFactory threadFactory = new ThreadFactoryBuilder().setNameFormat("excel-pool-%d").build();
    //線程池
    ExecutorService executorService=new ThreadPoolExecutor(30 , 50 ,
            1, TimeUnit.MINUTES, new LinkedBlockingQueue<>(100), threadFactory);
    //開啟多個線程分頁查數據

    executorService.submit(() -> {
        while (start.get()<=total) {
            //自增
            int pageNum = start.getAndAdd(pageSize);
            try {
                List<T> list = findPage(pageNum, pageSize,excelMapper,base);
                if (CollectionUtils.isEmpty(list)) {
                    break;
                }
                queue.put(list);
            } catch (Exception e) {
                //異常情況也要放入空集合，防止寫線程無法退出循環
                log.error("異常情況",e);
            }
        }
    });
    Future<?> submit = executorService.submit(() -> {
        while (writerCount.get()<total) {
            List<T> list = null;
            try{
                list = queue.take();
                writerCount.getAndAdd(list.size());
                writer.write(list, writeSheet);
            }catch (InterruptedException e){
            }

        }
        try{
            writer.finish();
        }catch (Exception e) {
            log.error("異常情況",e);
            System.out.println("6666");
        }finally {
            executorService.shutdown();
        }
    });
    try {
        // 阻塞等待完成，異步處理也可以去掉這段代碼
        submit.get();
    } catch (Exception e) {
        throw new RuntimeException(e);
    }finally {
        executorService.shutdown();
    }
}

private List<T> findPage(int pageNum, int pageSize, ExcelMapper excelMapper,Base base) {
    // todo 實現分頁查詢
    base.setPage(pageNum);
    base.setPageSize(pageSize);
    List<T> list=excelMapper.excelList(base);
    return list;
}