[Java] 下載檔案的中文編碼錯誤如何解決

當透過瀏覽器下載檔案時，需要處理不同瀏覽器對檔案名稱該如何正確編碼的問題。
可以參考[2]的實驗結果。

目前針對IE採用UrlEncode，chrome與firefox採用Mimetype base64編碼，其他未偵到的也都採用base64 :D，base64編碼可直接使用 MimeUtility.encodeText(fileName, "UTF-8", "B");即可。

範例碼如下：

String userBrowser = request.getHeader(HEADER_USER_AGENT);
       
       if(userBrowser != null){
        
        log.debug(String.format("User agent: %s", userBrowser));
        if(userBrowser.toLowerCase().indexOf("mozilla") > -1
          && userBrowser.toLowerCase().indexOf("msie") < 0 
          && userBrowser.toLowerCase().indexOf("chrome") < 0){
         
         log.debug("Detect 'FireFox' browser");
//         Mozilla/5.0 (Windows NT 6.1; WOW64; rv:25.0) Gecko/20100101 Firefox/25.0

         fileName = MimeUtility.encodeText(fileName, "UTF-8", "B");
         
        }else if(userBrowser.toLowerCase().indexOf("msie") > -1){
        
         log.debug("Detect 'IE' browser");
//         Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.1; WOW64; Trident/6.0; MATP)
         //cosa url encoder

         fileName = URLEncoder.encode(fileName);  
         
        }else{
        
//         Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/31.0.1650.57 Safari/537.36
         log.debug("Common attachment");
         
         fileName = MimeUtility.encodeText(fileName, "UTF-8", "B");
        }
       }
       else{
        
        log.debug("Cannot find User-Agent header");
        
//        encoding - the encoding to be used. Currently supported values are "B" and "Q".
//        If this parameter is null, then the "Q" encoding is used if most of characters to be encoded are in the ASCII charset, otherwise "B" encoding is used.
        fileName = MimeUtility.encodeText(fileName, "UTF-8", "B");

       }
       
       log.debug("Filename encoded:" + fileName);
       String contentDisposition = String.format("%s ;filename=\"%s\"", valOfDisposition, fileName);

       log.debug("Content diposition:" + contentDisposition);
       builder.header(HEADER_CONTENT_DISPOSITION,contentDisposition);

測試檔案:
ライセンス期限切中文中文kumokura_010507.exe

Base64編碼:

=?UTF-8?B?44Op44Kk44K744Oz44K55pyf6ZmQ5YiH5Lit5paH5Lit5paHa3Vt?= =?UTF-8?B?b2t1cmFfMDEwNTA3LmV4ZQ==?=

參考:
[1] 錯誤訊息：「Internet Explorer cannot download a file (Internet Explorer 無法下載檔案)」

[2] Unicode网页中上传下载文件时发生文件名乱码的问题