通过多线程读取数据,使用EasyExcel按顺序导出数据
导出时如果要保证顺序需要使用单线程,但是查询时可以用多线程,因为多线程查询后返回数据不是按照顺序排列的,所以我的思路是再循环时给每个线程打标识,通过标识来排序多线程返回的结果
创建一个Future对象,用于排序多线程查询结果
java
static class Result {
final Integer threadId;
final List<UserInfo> data;
Result(Integer threadId, List<UserInfo> data) {
this.threadId = threadId;
this.data = data;
}
}
java
@PostMapping("export3")
public void export3(HttpServletResponse response) throws IOException, InterruptedException, ExecutionException {
// 查询总数
Long dataCount = userInfoMapper.selectCount();
// 每页条数
Long searchCount = 100000L;
// 获取页数并向上取整 5.2 -> 6
int ceil = (int) Math.ceil((double) dataCount / searchCount);
// 使用线程池
ExecutorService executorService = Executors.newFixedThreadPool(Runtime.getRuntime().availableProcessors());
List<Future<Result>> futures = new ArrayList<>();
Map<Integer, Result> resultsMap = new ConcurrentHashMap<>();
// 通过多线程查询,并设置线程ID
for (int i = 1; i <= ceil; i++) {
Integer pageNum = Math.toIntExact((i - 1) * searchCount);
int finalI = i;
futures.add(executorService.submit(() -> new Result(finalI, userInfoMapper.getList(pageNum, searchCount))));
}
// 收集所有线程的结果
for (Future<Result> future : futures) {
resultsMap.put(future.get().threadId, future.get());
}
// 通过线程ID排序
List<Result> sortedResults = resultsMap.values().stream()
.sorted(Comparator.comparingInt(result -> result.threadId))
.collect(Collectors.toList());
// 构建表头
WriteCellStyle headWriteCellStyle = new WriteCellStyle();
headWriteCellStyle.setHorizontalAlignment(HorizontalAlignment.CENTER);
WriteCellStyle contentWriteCellStyle = new WriteCellStyle();
contentWriteCellStyle.setHorizontalAlignment(HorizontalAlignment.CENTER);
HorizontalCellStyleStrategy horizontalCellStyleStrategy = new HorizontalCellStyleStrategy(
headWriteCellStyle, contentWriteCellStyle);
// 设置返回格式
response.setHeader("Content-Disposition", "attachment; filename=test" + DateUtil.format(new Date(), "yyyyMMddHHmmss") + ".xlsx");
response.setContentType("application/vnd.ms-excel");
response.setCharacterEncoding("UTF-8");
ExcelWriter excelWriter = EasyExcelFactory.write(response.getOutputStream(), UserInfo.class)
.registerWriteHandler(horizontalCellStyleStrategy).needHead(true)
.excelType(ExcelTypeEnum.XLSX)
.build();
// 如果是单sheet,则放在循环外面,多sheet放在循环里面
WriteSheet writeSheet = EasyExcelFactory.writerSheet("Sheet1")
.head(UserInfo.class)
.registerWriteHandler(new LongestMatchColumnWidthStyleStrategy())
.registerWriteHandler(horizontalCellStyleStrategy)
.build();
try {
// 使用单线程写入Excel
sortedResults.forEach(r -> excelWriter.write(r.data, writeSheet));
} finally {
executorService.shutdown();
excelWriter.finish();
}
}