Java实现限制文件上传类型功能

public void validateFileType(MultipartFile file) {
    List<String> allowedTypes = List.of("image/png", "image/jpeg", "application/pdf");
    String contentType = file.getContentType();

    if (!allowedTypes.contains(contentType)) {
        throw new IllegalArgumentException("不支持的文件类型: " + contentType);
    }
}

public void validateExtension(MultipartFile file) {
    String filename = file.getOriginalFilename().toLowerCase();
    List<String> allowedExtensions = List.of(".jpg", ".jpeg", ".png", ".pdf");

    if (allowedExtensions.stream().noneMatch(filename::endsWith)) {
        throw new IllegalArgumentException("不支持的文件后缀");
    }
}

import org.apache.tika.Tika;

public void validateByTika(MultipartFile file) throws IOException {
    Tika tika = new Tika();
    String detectedType = tika.detect(file.getInputStream());

    List<String> allowedTypes = List.of("image/jpeg", "image/png", "application/pdf");
    if (!allowedTypes.contains(detectedType)) {
        throw new IllegalArgumentException("文件类型不合法: " + detectedType);
    }
}

@PostMapping("/upload")
public ResponseEntity<?> upload(@RequestParam MultipartFile file) throws IOException {
    validateFileType(file);      // 判断 MIME 类型
    validateExtension(file);     // 判断文件名后缀
    validateByTika(file);        // 推荐：更准确安全

    // 保存逻辑略...
    return ResponseEntity.ok("上传成功");
}

file:
  allowed-types:
    - image/png
    - image/jpeg
    - application/pdf

@ConfigurationProperties(prefix = "file")
@Data
public class FileConfig {
    private List<String> allowedTypes;
}

@Autowired
private FileConfig fileConfig;

if (!fileConfig.getAllowedTypes().contains(contentType)) {
    throw new IllegalArgumentException("不支持的文件类型");
}