序
本文主要研究一下如何使用webflux提升数据导出效率
传统导出
@GetMapping("/download-old") public ResponseEntity<Resource> downloadInOldWays(){ return ResponseEntity.ok() .header(HttpHeaders.CONTENT_DISPOSITION,"attachment; filename=demo.xls") .header("Accept-Ranges","bytes") .body(new ByteArrayResource(exportBytes(1000))); } public byte[] exportBytes(int dataRow){ StringBuilder output = new StringBuilder(); output.append(ExcelUtil.startWorkbook()); output.append(ExcelUtil.startSheet()); output.append(ExcelUtil.startTable()); output.append(ExcelUtil.writeTitleRow(Sets.newHashSet("title","content"))); IntStream.rangeClosed(1,dataRow).forEach(i -> { try { TimeUnit.MILLISECONDS.sleep(100); } catch (InterruptedException e) { e.printStackTrace(); } output.append(ExcelUtil.writeDataRow(Lists.newArrayList("title"+i,"content"+i))); }); output.append(ExcelUtil.endTable()); output.append(ExcelUtil.endSheet()); output.append(ExcelUtil.endWorkbook()); return output.toString().getBytes(StandardCharsets.UTF_8); }
这里模拟的是等所有数据都准备好了再导出,这种速度肯定慢,差不多需要等待100秒浏览器才能弹出下载框,如果前面有网关,很容易在网关那里超时了
webflux导出
@GetMapping("/download") public Mono<Void> downloadByWriteWith(ServerHttpResponse response) throws IOException { response.getHeaders().set(HttpHeaders.CONTENT_DISPOSITION,"attachment; filename=demo.xls"); response.getHeaders().add("Accept-Ranges","bytes"); Flux<DataBuffer> flux = excelService.export(1000); return response.writeWith(flux); } public Flux<DataBuffer> export(int dataRow){ return Flux.create(sink -> { sink.next(stringBuffer(ExcelUtil.startWorkbook())); sink.next(stringBuffer(ExcelUtil.startSheet())); sink.next(stringBuffer(ExcelUtil.startTable())); //write title row sink.next(stringBuffer(ExcelUtil.writeTitleRow(Sets.newHashSet("title","content")))); //write data row IntStream.rangeClosed(1,dataRow).forEach(i -> { try { TimeUnit.MILLISECONDS.sleep(100); } catch (InterruptedException e) { e.printStackTrace(); } sink.next(stringBuffer(ExcelUtil.writeDataRow(Lists.newArrayList("title"+i,"content"+i)))); }); sink.next(stringBuffer(ExcelUtil.endTable())); sink.next(stringBuffer(ExcelUtil.endSheet())); sink.next(stringBuffer(ExcelUtil.endWorkbook())); sink.complete(); }); }
这里使用ReactiveHttpOutputMessage的writeWith(Publisher<? extends DataBuffer> body)方法,实现边准备数据边导出
等待十几秒就弹下载框,之后就server端一边输出,浏览器一边下载,100秒左右下载完毕
小结
两种方法目前看来用时差不多,不过后者可以避免超时。当然使用传统mvc也可以实现类似效果,就是拿到response的输出流不断地write和flush。不过webflux可以配合reactive的repository,实现端到端的reactive stream,同时也可以避免OOM。