java接口导出csv

1、背景介绍

项目中需要导出数据质检结果，本来使用Excel，但是质检结果数据行数过多，导致用hutool报错，因此转为导出csv格式数据。

2、参考文档

https://blog.csdn.net/ityqing/article/details/127879556
工程环境：springboot 2.2.x

3、实现

controller

    @ApiOperation("导出质检结果csv")@GetMapping("/export/csv/{datasetId}")public void exportCsv( @PathVariable String datasetId,HttpServletResponse response) {CheckDataParamVO checkDataParamVO = new CheckDataParamVO();checkDataParamVO.setDatasetId(datasetId);checkDataService.exportCsv(checkDataParamVO, response);}

service

 /*** 导出csv格式质检结果** @param checkDataVO* @param response*/@Overridepublic void exportCsv(CheckDataParamVO checkDataVO, HttpServletResponse response) {List<CheckResultVO> res = getCheckResultAll(checkDataVO);String fileName = "质检结果表" + DateTime.now().getTime();writeCsv(response, fileName, res);}/*** CSV文件列分隔符*/private static final String CSV_COLUMN_SEPARATOR = ",";/*** CSV文件行分隔符*/private static final String CSV_ROW_SEPARATOR = System.lineSeparator();private static final List<String> titleName = Arrays.asList("序号", "异常类型", "图层名", "要素主键");/*** @param response 响应流* @param fileName 文件名称* @param dataList 数据源*/private void writeCsv(HttpServletResponse response, String fileName, List<CheckResultVO> dataList) {OutputStream out = null;try {StringBuffer buf = new StringBuffer();out = response.getOutputStream();String lastFileName = fileName + ".csv";response.setContentType("application/msexcel;charset=UTF-8");response.setHeader("Content-Disposition", "attachment; filename=" + URLEncoder.encode(lastFileName, "UTF-8"));// 组装表头for (String title : titleName) {buf.append(title).append(CSV_COLUMN_SEPARATOR);}buf.append(CSV_ROW_SEPARATOR);//组装行数据dataList.forEach(data -> {buf.append(Optional.ofNullable(data.getSid()).orElse(0)).append(CSV_COLUMN_SEPARATOR);buf.append(Optional.ofNullable(data.getCheckType()).orElse("")).append(CSV_COLUMN_SEPARATOR);buf.append(Optional.ofNullable(data.getSubname()).orElse("")).append(CSV_COLUMN_SEPARATOR);buf.append(Optional.ofNullable(data.getFid()).orElse("")).append(CSV_COLUMN_SEPARATOR);buf.append(CSV_ROW_SEPARATOR);});//添加bom，不加Excel打开中文会乱码out.write(new byte[]{(byte) 0xEF, (byte) 0xBB, (byte) 0xBF});out.write(buf.toString().getBytes("UTF-8"));} catch (Exception e) {log.error("导出CSV异常", e);} finally {if (out != null) {try {out.flush();out.close();} catch (IOException e) {log.error("导出CSV异常", e);}}}}

4、测试结果

可用
在这里插入图片描述

5、总结

以上是不使用第三方组件实现导出csv文件。测试成功。

6、补充

参考文章
https://blog.csdn.net/ityqing/article/details/127879556

6.1、bug

提到了一个中文乱码的bug
Excel 在读取 csv 的时候是通过读取文件头上的 bom 来识别编码的，这导致如果我们生成 csv 文件的平台输出无 bom 头编码的 csv 文件（例如 utf-8 ，在标准中默认是可以没有 bom 头的），Excel 只能自动按照默认编码读取，不一致就会出现乱码问题了。

6.2、解决：

写入的时候加上： out.write(new byte[] { (byte) 0xEF, (byte) 0xBB,(byte) 0xBF });

6.3、其他方式

参考文章用了两种方法，另一种是引入第三方组件CSVWriter
pom.xml文件增加依赖

<dependency><groupId>com.opencsv</groupId><artifactId>opencsv</artifactId><version>5.5.2</version>
</dependency>

java代码如下，自己没测。只是抄过来

/**
* @param response 响应流
* @param fileName 文件名称
* @param dataList  数据源
*/
private void writeCsv2(HttpServletResponse response, String fileName, List<TaskAplusExpire> dataList) {String lastFileName = fileName + ".csv";response.setContentType("application/msexcel;charset=UTF-8");try {response.setHeader("Content-Disposition", "attachment; filename="+ URLEncoder.encode(lastFileName, "UTF-8"));PrintWriter out = response.getWriter();// 手动加上BOM标识out.write(new String(new byte[] { (byte) 0xEF, (byte) 0xBB, (byte) 0xBF }));// 设置显示的顺序,数据源对象属性列表String[] columnMapping = { "pmid", "phone", "sendDate", "code", "message" };ColumnPositionMappingStrategy<TaskAplusExpire> mapper =new ColumnPositionMappingStrategy<TaskAplusExpire>();//数据源类型mapper.setType(TaskAplusExpire.class);mapper.setColumnMapping(columnMapping);// 写表头CSVWriter csvWriter = new CSVWriter(response.getWriter(), CSVWriter.DEFAULT_SEPARATOR,CSVWriter.NO_QUOTE_CHARACTER);String[] header = { "Pmid","Phone","Send Date","Code","Message"};csvWriter.writeNext(header);StatefulBeanToCsv beanToCsv = new StatefulBeanToCsvBuilder(out).withMappingStrategy(mapper).withQuotechar(CSVWriter.NO_QUOTE_CHARACTER).withSeparator(CSVWriter.DEFAULT_SEPARATOR).withEscapechar('\\').build();beanToCsv.write(dataList);csvWriter.close();out.close();} catch (IOException e) {e.printStackTrace();}catch (CsvDataTypeMismatchException e) {e.printStackTrace();} catch (CsvRequiredFieldEmptyException e) {e.printStackTrace();}