打包下载成.zip文件

项目背景

公司使用vue + SpringBoot实现批量下载功能
今天在调试批量下载这个功能。打包成.zip文件时，在返回给前端浏览器出现报错信息：
后端报错：

ERROR c.c.p.c.e.BusinessExceptionHandler - java.io.IOException: 你的主机中的软件中止了一个已建立的连接。
org.apache.catalina.connector.ClientAbortException: java.io.IOException: 你的主机中的软件中止了一个已建立的连接。

找了好久的错，发现浏览器的控制台有报错信息

Access to XMLHttpRequest at 'http://...:8097/pcsms-admin/batchExport/pdf?vids=1e7ed541bdd6b9f5614cca14623f8681,8dfda9f7151745ad5aa5f0abc2c55d5c' from origin 'http://..:8001' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource.

于是在后端中设置响应体，如 HttpServletResponse response ：

response.setHeader("Access-Control-Allow-Origin","*");

紧接着又出现如下的报错信息：

Access to XMLHttpRequest at 'http://...:8097/batchExport/pdf?vids=1e7ed541bdd6b9f5614cca14623f8681,8dfda9f7151745ad5aa5f0abc2c55d5c' from origin 'http://...:8001' has been blocked by CORS policy: The value of the 'Access-Control-Allow-Origin' header in the response must not be the wildcard '*' when the request's credentials mode is 'include'. The credentials mode of requests initiated by the XMLHttpRequest is controlled by the withCredentials attribute.

在面向百度编程中，找到一个帖子有详细的解释--axios设置withCredentials导致“跨域”的解决方案。检查前端配置果然有：

axios.defaults.withCredentials = true;

(一) 当前端配置withCredentials=true时, 后端配置Access-Control-Allow-Origin不能为*, 必须是相应地址
(二) 当配置withCredentials=true时, 后端需配置Access-Control-Allow-Credentials
(三) 当前端配置请求头时, 后端需要配置Access-Control-Allow-Headers为对应的请求头集合

于是我们可以采取方法一：axios.defaults.withCredentials = false;

在找其他解决方法时，找到一个可以不更改前端配置的方法二--Jquery Ajax设置withCredentials解决跨域请求，在response里加上以下两个header

response.addHeader("Access-Control-Allow-Origin", request.getHeader("Origin"));
// response.setHeader("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept");
response.addHeader("Access-Control-Allow-Credentials","true");

最后，终于问题成功解决。

后端代码：

1. TestController

@RequestMapping(value = "/batchExport/pdf", method = RequestMethod.POST)
public void batchExportPdf(HttpServletRequest request, HttpServletResponse response, @RequestParam("vids") String vids) throws Exception {
        //获取uavFileId，不进行xss过滤
//        HttpServletRequest orgRequest = XssHttpServletRequestWrapper.getOrgRequest(request);
//        String ids = orgRequest.getParameter("vids");
        String[] vid = vids.split(",");
        byte[] data = sopService.batchExportPdf(vid);

        String fileName = URLEncoder.encode("批量下载PDF" + DateUtils.format(new Date(), "yyyyMMddHHmmss") + ".zip", "UTF-8");

        response.reset();
        // 当前端配置withCredentials=true时, 后端配置Access-Control-Allow-Origin不能为*, 必须是相应地址
        response.addHeader("Access-Control-Allow-Origin", request.getHeader("Origin"));
        // 这个若不起作用，使用下面的"FileName"的
//        response.addHeader("Access-Control-Expose-Headers","*");
        response.addHeader("Access-Control-Allow-Methods", "GET,POST,PUT,DELETE");
        // 设置在下载框默认显示的文件名
        response.setHeader("Content-disposition", "attachment;filename=" + fileName + ";" + "filename*=utf-8''" + fileName);
        response.setHeader("FileName",  fileName);
        // 让axios放行指定的响应头 https://blog.csdn.net/u012586326/article/details/125790079
        response.addHeader("Access-Control-Expose-Headers","FileName");
        // 写明文件大小
        response.addHeader("Content-Length", "" + data.length);
        // 指明response的返回对象是文件流
        response.setContentType("application/octet-stream; charset=UTF-8");
        response.setCharacterEncoding("UTF-8");
        // 当前端配置withCredentials=true时, 后端需配置Access-Control-Allow-Credentials
        response.addHeader("Access-Control-Allow-Credentials","true");

        IOUtils.write(data, response.getOutputStream());

    }

2. TestService

    /**
     * 批量下载pdf
     * @param vids
     * @return
     */
    byte[] batchExportPdf(String[] vids) throws Exception;

3. TestServiceImpl

    @Override
    public byte[] batchExportPdf(String[] vids) {
        ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
        // 用于将数据压缩成Zip文件格式
        ZipOutputStream zipOut = new ZipOutputStream(outputStream);
        FileInputStream inputStream = null;
        List<String> deletePdf = new ArrayList<>();
        List<FileInputStream> in = new ArrayList<>();
        try {
            for (String vid : vids) {
                // 下载到本地
                // PdfDTO包含：pdfPath（本地PDF路径）、fileName（下载后的文件名（不含文件后缀.pdf））
                PdfDTO dto = exportPdfByVid(vid);
                if (!ObjectUtils.isEmpty(dto)) {
                    zipOut.putNextEntry(new ZipEntry((Objects.requireNonNull(dto.getFileName())) + ".pdf"));
                    inputStream = new FileInputStream(new File(dto.getPdfPath()));
                    int len;
                    byte[] bytes = new byte[1024];
                    while ((len = inputStream.read(bytes)) != -1) {
                        zipOut.write(bytes, 0, len);
                    }
                    //关闭该zip文件中打开的项
                    zipOut.closeEntry();
                    deletePdf.add(dto.getPdfPath());
                    in.add(inputStream);
                }
            }
        } catch (Exception e) {
            log.error("批量下载时出现错误：" + e.toString());
            throw new BusinessException("批量下载时出现错误：" + e.getMessage());
        } finally {
            try {
                for (FileInputStream stream : in) {
                    stream.close();
                }
                // 关流
                IOUtils.closeQuietly(zipOut);
            } catch (IOException e) {
                log.error("批量下载时流关闭异常：" + e.toString());
            }
            // 删除源文件（我这里是因为从数据服务器下载了文件到本地，所以删掉本地的）
            File file = null;
            for (String s : deletePdf) {
                file = new File(s);
                file.delete();
            }
        }
        return outputStream.toByteArray();
    }

参考：
https://blog.csdn.net/cckevincyh/article/details/81140443
https://developer.mozilla.org/zh-CN/docs/Web/HTTP/Headers/Access-Control-Allow-Origin
https://blog.csdn.net/baidu_28068985/article/details/105558280
https://blog.csdn.net/HermitSun/article/details/100797223