javaweb實現檔案下載

• 實現檔案下載
• 解決下載檔名帶有中文亂碼問題

效果圖

實現思路

根據請求連接獲取檔名和檔案型別,設定響應頭,獲取輸入流和輸出流

核心程式碼

public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
    {
        String fileName = request.getParameter("fileName");
        //獲得請求頭中的User-Agent
 

        String agent = request.getHeader("User-Agent");
        //根據不同瀏覽器進行不同的編碼
        String fileNameEncoder = "";
        if (agent.contains("MSIE")) {
            // IE瀏覽器
            fileNameEncoder = URLEncoder.encode(fileName, "utf-8");
            fileNameEncoder = fileNameEncoder.replace("+", " "
 
);
        } else if (agent.contains("Firefox")) {
            // 火狐瀏覽器
            BASE64Encoder base64Encoder = new BASE64Encoder();
            fileNameEncoder = "=?utf-8?B?"+ base64Encoder.encode(fileName.getBytes("utf-8")) + "?=";
        } else {
            // 其它瀏覽器
            fileNameEncoder = URLEncoder.encode(fileName, "utf-8"
 
);             
        }
        //告訴瀏覽器解析檔案的型別
        response.setContentType(this.getServletContext().getMimeType(fileName));
        //告訴瀏覽器不能解析檔案且適配各種瀏覽器提供檔案預設的名稱
        response.setHeader("Content-Disposition", "attachment;filename="+fileNameEncoder); 
        String realPath = getServletContext().getRealPath(fileName);
        InputStream in = new FileInputStream(realPath);
        ServletOutputStream out = response.getOutputStream();
        int len = 0;
        byte[] bytes = new byte[1024];
        while ((len = in.read(bytes)) > 0)
        {
            out.write(bytes, 0, len);   
        }
        out.close();
        in.close();
    }

重點

1. response.setHeader(“Content-Disposition”, “attachment;filename=”+fileNameEncoder); 實現強制下載
2. response.setContentType(this.getServletContext().getMimeType(fileName)); 可以省略
3. 解決檔名稱亂碼問題
   if (agent.contains(“MSIE”)) {
   // IE瀏覽器
   fileNameEncoder = URLEncoder.encode(fileName, “utf-8”);
   fileNameEncoder = fileNameEncoder.replace(“+”, ” “);
   } else if (agent.contains(“Firefox”)) {
   // 火狐瀏覽器
   BASE64Encoder base64Encoder = new BASE64Encoder();
   fileNameEncoder = “=?utf-8?B?”+ base64Encoder.encode(fileName.getBytes(“utf-8”)) + “?=”;
   } else {
   // 其它瀏覽器
   fileNameEncoder = URLEncoder.encode(fileName, “utf-8”);
   }