在Java Spring框架中实现BLOB类型的附件下载的详细步骤

@GetMapping("/download/{id}")
public void download(@PathVariable("id") Integer id, HttpServletResponse response) throws IOException {
    Attachment attachment = attachmentService.findById(id);
    if (attachment == null || attachment.getFileContent() == null) {
        throw new RuntimeException("File not found");
    }
    
    // 设置响应头信息
    response.setContentType(attachment.getContentType());
    response.setContentLength(attachment.getFileContent().length);
    response.setHeader(HttpHeaders.CONTENT_DISPOSITION, "attachment; filename=" + 
                       new String(attachment.getFileName().getBytes(StandardCharsets.UTF_8), StandardCharsets.ISO_8859_1));
    
    // 将文件内容写入到响应流中
    try (OutputStream out = response.getOutputStream()) {
        out.write(attachment.getFileContent());
        out.flush();
    }
}

@GetMapping("/stream-download/{id}")
public ResponseEntity<InputStreamResource> streamDownload(@PathVariable("id") Integer id) throws IOException {
    Attachment attachment = attachmentService.findById(id);
    if (attachment == null || attachment.getFileContent() == null) {
        return ResponseEntity.notFound().build();
    }
    
    InputStream inputStream = new ByteArrayInputStream(attachment.getFileContent());
    HttpHeaders headers = new HttpHeaders();
    headers.add(HttpHeaders.CONTENT_DISPOSITION, "attachment; filename=" + 
                new String(attachment.getFileName().getBytes(StandardCharsets.UTF_8), StandardCharsets.ISO_8859_1));
    headers.add(HttpHeaders.CONTENT_TYPE, attachment.getContentType());
    
    return ResponseEntity.ok()
            .headers(headers)
            .contentLength(attachment.getFileContent().length)
            .body(new InputStreamResource(inputStream));
}

<a href="/download/1" rel="external nofollow"  download="example.pdf">Download PDF</a>

function downloadFile(fileId) {
    fetch(`/download/${fileId}`)
        .then(response => response.blob())
        .then(blob => {
            const url = window.URL.createObjectURL(blob);
            const a = document.createElement('a');
            a.style.display = 'none';
            a.href = url;
            a.download = 'example.pdf'; // 可以根据实际情况调整文件名
            document.body.appendChild(a);
            a.click();
            window.URL.revokeObjectURL(url);
            document.body.removeChild(a);
        })
        .catch(console.error);
}