Java：一种将 Mime（内容）类型与 CommonsMultipartFile 中的文件扩展名相匹配的方法

在我的公司，出于额外原因，我需要将 mime 类型与文件扩展名进行比较。我有一个CommonsMultipartFile。我正在尝试找出进行这种比较的最佳方法。我见过一个MimetypesFileTypeMap，但不确定这是否适用于此。我试图避免（或限制）任何硬编码。

我得到的值是这样的：

CommonsMultipartFile file = ...;
String fileName = file.getOriginalFilename();
String contentType = file.getContentType();

String extension = FilenameUtils.getExtension(fileName);

我感谢任何对此的指导和帮助。谢谢！

用于这种情况的 Java 库非常有限（类型数量）。我就是这样做的：

static String getMimeType(String fileName) {
    // 1. first use java's built-in utils
    FileNameMap mimeTypes = URLConnection.getFileNameMap();
    String contentType = mimeTypes.getContentTypeFor(fileName);

    // 2. nothing found -> lookup our in extension map to find types like ".doc" or ".docx"
    if (contentType == null) {
        String extension = fileName.substring(fileName.lastIndexOf('.') + 1, fileName.length());;
        contentType = fileExtensionMap.get(extension);
    }
    return contentType;
}

第 2 步涉及拥有静态地图：

private static final Map<String, String> fileExtensionMap;

static {
    fileExtensionMap = new HashMap<String, String>();
    // MS Office
    fileExtensionMap.put("doc", "application/msword");
    fileExtensionMap.put("dot", "application/msword");
    fileExtensionMap.put("docx", "application/vnd.openxmlformats-officedocument.wordprocessingml.document");
    fileExtensionMap.put("dotx", "application/vnd.openxmlformats-officedocument.wordprocessingml.template");
    fileExtensionMap.put("docm", "application/vnd.ms-word.document.macroEnabled.12");
    fileExtensionMap.put("dotm", "application/vnd.ms-word.template.macroEnabled.12");
    fileExtensionMap.put("xls", "application/vnd.ms-excel");
    fileExtensionMap.put("xlt", "application/vnd.ms-excel");
    fileExtensionMap.put("xla", "application/vnd.ms-excel");
    fileExtensionMap.put("xlsx", "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet");
    fileExtensionMap.put("xltx", "application/vnd.openxmlformats-officedocument.spreadsheetml.template");
    fileExtensionMap.put("xlsm", "application/vnd.ms-excel.sheet.macroEnabled.12");
    fileExtensionMap.put("xltm", "application/vnd.ms-excel.template.macroEnabled.12");
    fileExtensionMap.put("xlam", "application/vnd.ms-excel.addin.macroEnabled.12");
    fileExtensionMap.put("xlsb", "application/vnd.ms-excel.sheet.binary.macroEnabled.12");
    fileExtensionMap.put("ppt", "application/vnd.ms-powerpoint");
    fileExtensionMap.put("pot", "application/vnd.ms-powerpoint");
    fileExtensionMap.put("pps", "application/vnd.ms-powerpoint");
    fileExtensionMap.put("ppa", "application/vnd.ms-powerpoint");
    fileExtensionMap.put("pptx", "application/vnd.openxmlformats-officedocument.presentationml.presentation");
    fileExtensionMap.put("potx", "application/vnd.openxmlformats-officedocument.presentationml.template");
    fileExtensionMap.put("ppsx", "application/vnd.openxmlformats-officedocument.presentationml.slideshow");
    fileExtensionMap.put("ppam", "application/vnd.ms-powerpoint.addin.macroEnabled.12");
    fileExtensionMap.put("pptm", "application/vnd.ms-powerpoint.presentation.macroEnabled.12");
    fileExtensionMap.put("potm", "application/vnd.ms-powerpoint.presentation.macroEnabled.12");
    fileExtensionMap.put("ppsm", "application/vnd.ms-powerpoint.slideshow.macroEnabled.12");
    // Open Office
    fileExtensionMap.put("odt", "application/vnd.oasis.opendocument.text");
    fileExtensionMap.put("ott", "application/vnd.oasis.opendocument.text-template");
    fileExtensionMap.put("oth", "application/vnd.oasis.opendocument.text-web");
    fileExtensionMap.put("odm", "application/vnd.oasis.opendocument.text-master");
    fileExtensionMap.put("odg", "application/vnd.oasis.opendocument.graphics");
    fileExtensionMap.put("otg", "application/vnd.oasis.opendocument.graphics-template");
    fileExtensionMap.put("odp", "application/vnd.oasis.opendocument.presentation");
    fileExtensionMap.put("otp", "application/vnd.oasis.opendocument.presentation-template");
    fileExtensionMap.put("ods", "application/vnd.oasis.opendocument.spreadsheet");
    fileExtensionMap.put("ots", "application/vnd.oasis.opendocument.spreadsheet-template");
    fileExtensionMap.put("odc", "application/vnd.oasis.opendocument.chart");
    fileExtensionMap.put("odf", "application/vnd.oasis.opendocument.formula");
    fileExtensionMap.put("odb", "application/vnd.oasis.opendocument.database");
    fileExtensionMap.put("odi", "application/vnd.oasis.opendocument.image");
    fileExtensionMap.put("oxt", "application/vnd.openofficeorg.extension");
    // Other
    fileExtensionMap.put("txt", "text/plain");
    fileExtensionMap.put("rtf", "application/rtf");
    fileExtensionMap.put("pdf", "application/pdf");
}

对我来说效果很好，希望有帮助！