java - 如何使用 spring boot 压缩下载的文件

Question

我是 java 初学者，需要一些帮助来使用 MSSQL 后端的 REST API 调用来压缩下载的文件。下面的代码片段将 ID 作为输入参数，获取特定于该 ID 的记录并将其下载到本地。我现在需要修改代码以在下载文件时压缩文件。

@GetMapping("/message/save")
    @CrossOrigin(origins = "*")
    public ResponseEntity<byte[]> download(@RequestParam("id") Long id) throws Exception {
        Optional<MessageEntity> messageRecord = messageRepository.findById(id);
        MessageEntity messageEntity = messageRecord.get();
        ObjectMapper objectMapper = new ObjectMapper();
        String xml = objectMapper.writeValueAsString(messageEntity);
        byte[] isr = xml.getBytes();
        String fileName = "message.zip";
        HttpHeaders respHeaders = new HttpHeaders();
        respHeaders.setContentLength(isr.length);
        respHeaders.setContentType(MediaType.APPLICATION_OCTET_STREAM);
        respHeaders.set(HttpHeaders.CONTENT_DISPOSITION, "attachment; filename=" + fileName);
        return new ResponseEntity<byte[]>(isr, respHeaders, HttpStatus.OK);
    }

我希望输出是一个压缩文件。

Answer 1

我不确定我是否清楚地理解了您的问题。但我假设您只需要从字符串制作 zip:

@GetMapping("/message/save")
@CrossOrigin(origins = "*")
public void download(@RequestParam("id") Long id, HttpServletRequest request,
                     HttpServletResponse response) throws Exception {
    MessageEntity messageEntity = messageRepository.findById(id).orElseThrow(() -> new Exception("Not found!"));
    String xml = new ObjectMapper().writeValueAsString(messageEntity);
    String fileName = "message.zip";
    String xml_name = "message.xml";
    byte[] data = xml.getBytes();
    byte[] bytes;
    try (ByteOutputStream fout = new ByteOutputStream();
         ZipOutputStream zout = new ZipOutputStream(fout)) {
        zout.setLevel(1);
        ZipEntry ze = new ZipEntry(xml_name);
        ze.setSize(data.length);
        zout.putNextEntry(ze);
        zout.write(data);
        zout.closeEntry();
        bytes = fout.getBytes();
    }
    response.setContentType("application/zip");
    response.setContentLength(bytes.length);
    response.setHeader("Content-Disposition",
            "attachment; "
                    + String.format("filename*=" + StandardCharsets.UTF_8.name() + "''%s", fileName));
    ServletOutputStream outputStream = response.getOutputStream();
    FileCopyUtils.copy(bytes, outputStream);
    outputStream.close();
}