一、背景
有一次项目的需求要求导出excel，并且将不同的数据分别写到不同的sheet中。
二、 方案概述
首先一开始使用easyexcel去导出excel，结果发现导出时间需要3秒左右。于是想着能不能缩短excel导出时间，于是第一次尝试使用异步线程去查询数据库，却发现接口的时间并没有明显缩短，于是自己就开始排查耗时的操作，于是发现是写sheet的时候是串行执行，并且每个写sheet的时间并不短，尤其在sheet比较多的时候，会导致导出的时间比较长。于是，想着能不能使用异步线程并发去写sheet，但是，使用的时候报错。后来去找报错的原因，是因为easyexcel并不支持并发写。于是，我就转战POI。尝试是否能够并发写入多个sheet。
使用easyexcel写入多个sheet
java
try {
response.setContentType("application/vnd.openxmlformats-officedocument.spreadsheetml.sheet");
response.setCharacterEncoding("utf-8");
// 这里URLEncoder.encode可以防止中文乱码 当然和easyexcel没有关系
String fileName = URLEncoder.encode(EXCEL, "UTF-8").replaceAll("\\+", "%20");
response.setHeader("Content-disposition", "attachment;filename*=utf-8''" + fileName + ".xlsx");
AtomicInteger atomicInteger = new AtomicInteger(0);
ExcelWriter build = EasyExcel.write(response.getOutputStream(),VirtualInstanceDataPoint.class).build();
list.stream().map(i -> CompletableFuture.supplyAsync(() -> {
return service.list();
}, executor)).collect(Collectors.toList()).stream()
.map(CompletableFuture::join).collect(Collectors.toList()).forEach(r->{
int andIncrement = atomicInteger.getAndIncrement();
WriteSheet build1 = EasyExcel.writerSheet(andIncrement, r.get(0).getDevice() + andIncrement).build();
build.write(r, build1);
});
build.finish();
response.flushBuffer();
} catch (Exception e) {
// 重置response
response.reset();
response.setContentType("application/json");
response.setCharacterEncoding("utf-8");
response.getWriter().println(JSON.toJSONString(R.error().message(e.getMessage()).code(20007)));
}并发写入多个sheet会报
org.apache.poi.openxml4j.exceptions.PartAlreadyExistsException: A part with the name '/xl/worksheets/sheet1.xml' already exists : Packages shall not contain equivalent part names and package implementers shall neither create nor recognize packages with equivalent part names. [M1.12]
POI写入多个sheet
java
String[] EXPORT_HEADER = {"head1","head2"};
@GetMapping("export3")
@ApiOperation(value = "excel导出信息")
@SneakyThrows
public void export3(HttpServletResponse response) {
OutputStream outputStream = response.getOutputStream();
response.reset();
response.setContentType("application/vnd.ms-excel");
response.setHeader("Content-disposition", "attachment;filename=template.xls");
AtomicInteger atomicInteger = new AtomicInteger();
HSSFWorkbook workbook = new HSSFWorkbook();
Font font = workbook.createFont();
font.setBold(true);
HSSFCellStyle cellStyle = workbook.createCellStyle();
cellStyle.setAlignment(HorizontalAlignment.CENTER);
cellStyle.setVerticalAlignment(VerticalAlignment.CENTER);
cellStyle.setFont(font);
List<IndexData> indexDatas = new ArrayList<>();
indexDatas.add(new IndexData("1",1.1));
indexDatas.add(new IndexData("2",2.2));
indexDatas.add(new IndexData("3",3.3));
for (IndexData indexData : indexDatas) {
HSSFSheet sheet = workbook.createSheet(indexData.getStr());
HSSFRow row = sheet.createRow(0);
// 创建表头
for (int i = 0; i < EXPORT_HEADER.length; i++) {
HSSFCell cell = row.createCell(i);
cell.setCellValue(EXPORT_HEADER[i]);
cell.setCellStyle(cellStyle);
}
row = sheet.createRow(1);
row.createCell(0).setCellValue(indexData.getStr());
row.createCell(1).setCellValue(indexData.getDoubleData());
}
workbook.write(outputStream);
outputStream.flush();
outputStream.close();
}
static class IndexData {
public IndexData(String string, Double doubleData) {
this.str = string;
this.doubleData = doubleData;
}
public String getStr() {
return str;
}
public Double getDoubleData() {
return doubleData;
}
private String str;
private Double doubleData;
}POI多线程写多个sheet
java
String[] EXPORT_HEADER = {"head1","head2"};
@GetMapping("export3")
@ApiOperation(value = "excel导出")
@SneakyThrows
public void export3(HttpServletResponse response) {
OutputStream outputStream = response.getOutputStream();
response.reset();
response.setContentType("application/vnd.ms-excel");
response.setHeader("Content-disposition", "attachment;filename=template.xls");
AtomicInteger atomicInteger = new AtomicInteger();
HSSFWorkbook workbook = new HSSFWorkbook();
Font font = workbook.createFont();
font.setBold(true);
HSSFCellStyle cellStyle = workbook.createCellStyle();
cellStyle.setAlignment(HorizontalAlignment.CENTER);
cellStyle.setVerticalAlignment(VerticalAlignment.CENTER);
cellStyle.setFont(font);
List<IndexData> indexDatas = new ArrayList<>();
indexDatas.add(new IndexData("1",1.1));
indexDatas.add(new IndexData("2",2.2));
indexDatas.add(new IndexData("3",3.3));
indexDatas.stream().map(data ->CompletableFuture.runAsync(() ->{
HSSFSheet sheet = workbook.createSheet(data.getStr());
HSSFRow row = sheet.createRow(0);
// 创建表头
for (int i = 0; i < EXPORT_HEADER.length; i++) {
HSSFCell cell = row.createCell(i);
cell.setCellValue(EXPORT_HEADER[i]);
cell.setCellStyle(cellStyle);
}
row = sheet.createRow(1);
row.createCell(0).setCellValue(data.getStr());
row.createCell(1).setCellValue(data.getDoubleData());
})).collect(Collectors.toList()).stream().map(CompletableFuture::join).collect(Collectors.toList());
workbook.write(outputStream);
outputStream.flush();
outputStream.close();
}
static class IndexData {
public IndexData(String string, Double doubleData) {
this.str = string;
this.doubleData = doubleData;
}
public String getStr() {
return str;
}
public Double getDoubleData() {
return doubleData;
}
private String str;
private Double doubleData;
}但是有时候会报错
java.lang.IllegalArgumentException: calculated end index (2576) is out of allowable range (2564..2569)
是因为在 子线程中创建sheet产生并发。
一个解决方案是主线程预先创建sheet
另一个方案是为创建sheet的操作加锁
java
@GetMapping("export1")
@ApiOperation(value = "excel导出信息")
@SneakyThrows
public void export2(HttpServletResponse response) {
OutputStream outputStream = response.getOutputStream();
response.reset();
response.setContentType("application/vnd.ms-excel");
response.setHeader("Content-disposition", "attachment;filename=template.xls");
AtomicInteger atomicInteger = new AtomicInteger();
HSSFWorkbook workbook = new HSSFWorkbook();
Font font = workbook.createFont();
font.setBold(true);
HSSFCellStyle cellStyle = workbook.createCellStyle();
cellStyle.setAlignment(HorizontalAlignment.CENTER);
cellStyle.setVerticalAlignment(VerticalAlignment.CENTER);
cellStyle.setFont(font);
list.stream().map(instanceId -> CompletableFuture.runAsync(() -> {
List<> collect = service.list();
HSSFSheet sheet = workbook.createSheet(collect.get(0).getDevice()+ atomicInteger.getAndIncrement());
HSSFRow row = sheet.createRow(0);
// 创建表头
for (int i = 0; i < EXPORT_HEADER.length; i++) {
HSSFCell cell = row.createCell(i);
cell.setCellValue(EXPORT_HEADER[i]);
cell.setCellStyle(cellStyle);
}
for (int i = 0; i < collect.size(); i++) {
row = sheet.createRow(i + 1);
row.createCell(0).setCellValue(collect.get(i).getInstanceId());
row.createCell(1).setCellValue(collect.get(i).getDevice());
row.createCell(2).setCellValue(collect.get(i).getDataId());
row.createCell(3).setCellValue(collect.get(i).getDataName());
}
}, executor)).collect(Collectors.toList()).stream()
.map(CompletableFuture::join).collect(Collectors.toList());
workbook.write(outputStream);
outputStream.flush();
outputStream.close();
}以下使用加锁方式
java
String[] EXPORT_HEADER = {"head1","head2"};
@GetMapping("export3")
@ApiOperation(value = "excel导出信息")
@SneakyThrows
public void export3(HttpServletResponse response) {
OutputStream outputStream = response.getOutputStream();
response.reset();
response.setContentType("application/vnd.ms-excel");
response.setHeader("Content-disposition", "attachment;filename=template.xls");
AtomicInteger atomicInteger = new AtomicInteger();
HSSFWorkbook workbook = new HSSFWorkbook();
Font font = workbook.createFont();
font.setBold(true);
HSSFCellStyle cellStyle = workbook.createCellStyle();
cellStyle.setAlignment(HorizontalAlignment.CENTER);
cellStyle.setVerticalAlignment(VerticalAlignment.CENTER);
cellStyle.setFont(font);
List<IndexData> indexDatas = new ArrayList<>();
indexDatas.add(new IndexData("1",1.1));
indexDatas.add(new IndexData("2",2.2));
indexDatas.add(new IndexData("3",3.3));
indexDatas.stream().map(data ->CompletableFuture.runAsync(() ->{
HSSFSheet sheet = getSheet(data, workbook);
HSSFRow row = sheet.createRow(0);
// 创建表头
for (int i = 0; i < EXPORT_HEADER.length; i++) {
HSSFCell cell = row.createCell(i);
cell.setCellValue(EXPORT_HEADER[i]);
cell.setCellStyle(cellStyle);
}
row = sheet.createRow(1);
row.createCell(0).setCellValue(data.getStr());
row.createCell(1).setCellValue(data.getDoubleData());
})).collect(Collectors.toList()).stream().map(CompletableFuture::join).collect(Collectors.toList());
workbook.write(outputStream);
outputStream.flush();
outputStream.close();
}
@org.jetbrains.annotations.NotNull
private synchronized static HSSFSheet getSheet(IndexData data, HSSFWorkbook workbook) {
HSSFSheet sheet = workbook.createSheet(data.getStr());
return sheet;
}但是这种方式还是会有一些并发带来的错误。
java.lang.NullPointerException: null
at org.apache.poi.hssf.record.SSTSerializer.serialize(SSTSerializer.java:70)
at org.apache.poi.hssf.record.SSTRecord.serialize(SSTRecord.java:279)
at org.apache.poi.hssf.record.cont.ContinuableRecord.getRecordSize(ContinuableRecord.java:60)
at org.apache.poi.hssf.model.InternalWorkbook.getSize(InternalWorkbook.java:1072)
at org.apache.poi.hssf.usermodel.HSSFWorkbook.getBytes(HSSFWorkbook.java:1474)
at org.apache.poi.hssf.usermodel.HSSFWorkbook.write(HSSFWorkbook.java:1386)
at org.apache.poi.hssf.usermodel.HSSFWorkbook.write(HSSFWorkbook.java:1374)
但是在本机实测100个线程10个循环出错的个数在20-30之间
我们可以捕获这些错误使用do while循环，当出错的时候可以清空状态再次重试。
总结：
该方法只是本菜鸡的愚见，使用这种方式的确可以完成并发写sheet，缩短接口的相应速度，将3秒左右的接口降低到50ms左右。应该能适合sheet略多，但并发量、数据量不多的excel导出，但本人也是第一次使用POI,所以可能有错误，希望大佬们能够多多指点。