Java Spring返回以BOM表以UTF-8编码的CSV文件 [英] Java Spring returning CSV file encoded in UTF-8 with BOM

问题描述

显然，对于excel来说，它可以很好地打开CSV文件，它的开头应具有字节顺序标记. CSV的下载是通过在控制器中写入HttpServletResponse的输出流来实现的，因为在请求期间会生成数据.当我尝试写入BOM表字节-java.io.CharConversionException: Not an ISO 8859-1 character: []时出现异常(即使我指定的编码为UTF-8).

Apparently for excel to open CSV files nicely, it should have the Byte Order Mark at the start. The download of CSV is implemented by writing into HttpServletResponse's output stream in the controller, as the data is generated during request. I get an exception when I try to write the BOM bytes - java.io.CharConversionException: Not an ISO 8859-1 character: [] (even though the encoding I specified is UTF-8).

有问题的控制器方法

@RequestMapping("/monthly/list")
public List<MonthlyDetailsItem> queryDetailsItems(
        MonthlyDetailsItemQuery query,
        @RequestParam(value = "format", required = false) String format,
        @RequestParam(value = "attachment", required = false, defaultValue="false") Boolean attachment,
        HttpServletResponse response) throws Exception 
{   
    // load item list
    List<MonthlyDetailsItem> list = detailsSvc.queryMonthlyDetailsForList(query);
    // adjust format
    format = format != null ? format.toLowerCase() : "json";
    if (!Arrays.asList("json", "csv").contains(format)) format = "json";

    // modify common response headers
    response.setCharacterEncoding("UTF-8");
    if (attachment)
        response.setHeader("Content-Disposition", "attachment;filename=duomenys." + format);

    // build csv
    if ("csv".equals(format)) {
        response.setContentType("text/csv; charset=UTF-8");
        response.getOutputStream().print("\ufeff");
        response.getOutputStream().write(buildMonthlyDetailsItemCsv(list).getBytes("UTF-8"));
        return null;
    }

    return list;
}

推荐答案

我刚遇到类似的问题.对我有用的解决方案是从响应对象获取输出流，并按如下所示对其进行写入

I have just come across, this same problem. The solution which works for me is to get the output stream from the response Object and write to it as follows

    // first create an array for the Byte Order Mark
    final byte[] bom = new byte[] { (byte) 239, (byte) 187, (byte) 191 }; 
    try (OutputStream os = response.getOutputStream()) {
        os.write(bom);

        final PrintWriter w = new PrintWriter(new OutputStreamWriter(os, "UTF-8"));
        w.print(data);
        w.flush();
        w.close();
    } catch (IOException e) {
        // logit
    }

因此在OutputStreamWriter上指定了UTF-8.

So UTF-8 is specified on the OutputStreamWriter.

作为补充，我应该补充一点，同一应用程序需要允许用户上传文件，这些文件可能带有或不带有BOM.这可以通过使用类org.apache.commons.io.input.BOMInputStream来解决，然后使用该类来构造org.apache.commons.csv.CSVParser. BOMInputStream包括方法hasBOM()，用于检测文件是否具有BOM. 我首先陷入的一个陷阱是hasBOM()方法从基础流中读取(很明显！)，因此处理此问题的方法是先标记该流，然后在测试是否它没有BOM表，请重置流.我为此使用的代码如下:

As an addendum to this, I should add, the same application needs to allow users to upload files, these may or may not have BOM's. This may be dealt with by using the class org.apache.commons.io.input.BOMInputStream, then using that to construct a org.apache.commons.csv.CSVParser. The BOMInputStream includes a method hasBOM() to detect if the file has a BOM or not. One gotcha that I first fell into was that the hasBOM() method reads (obviously!) from the underlying stream, so the way to deal with this is to first mark the stream, then after the test if it doesn't have a BOM, reset the stream. The code I use for this looks like the following:

try (InputStream is = uploadFile.getInputStream();
        BufferedInputStream buffIs = new BufferedInputStream(is);
        BOMInputStream bomIn = new BOMInputStream(buffIs);) {
      buffIs.mark(LOOKAHEAD_LENGTH);
      // this should allow us to deal with csv's with or without BOMs
      final boolean hasBOM = bomIn.hasBOM();
      final BufferedReader buffReadr = new BufferedReader(
          new InputStreamReader(hasBOM ? bomIn : buffIs, StandardCharsets.UTF_8));

      // if this stream does not have a BOM, then we must reset the stream as the test
      // for a BOM will have consumed some bytes
      if (!hasBOM) {
        buffIs.reset();
      }

      // collect the validated entity details
      final CSVParser parser = CSVParser.parse(buffReadr,
          CSVFormat.DEFAULT.withFirstRecordAsHeader());
      // Do stuff with the parser
      ...
  // Catch and clean up

希望这对某人有帮助.

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