檔名是英文的：

public void doGet(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
        
    String path = this.getServletContext().getRealPath("/download/1.jpg");
    String filename = path.substring(path.lastIndexOf("\\") + 1);
        
    response.setHeader("content-disposition", "attachment;filename=" + filename);
        
    InputStream in = null;
    ServletOutputStream out = null;
    try{
        in = new FileInputStream(path);
        int len = 0;
        byte buffer[] = new byte[1024];
        out = response.getOutputStream();
        while((len = in.read(buffer)) > 0){
            out.write(buffer, 0, len);
        }
    }finally{
        if(in != null){
            try{
                in.close();
            }catch(Exception e){
                e.printStackTrace();
            }
        }
        if(out != null){
            try{
                out.close();
            }catch(Exception e){
                e.printStackTrace();
            }
        }
    }
}
 

檔名含有中文，可用程式碼：

private void test2(HttpServletResponse response)
        throws FileNotFoundException, IOException {
    String path = this.getServletContext().getRealPath("/download/黑客.jpg");
    String filename = path.substring(path.lastIndexOf("\\") + 1);
        
    response.setHeader("content-disposition", "attachment;filename=" + URLEncoder.encode(filename,"UTF-8"));
        
    InputStream in = null;
    ServletOutputStream out = null;
    try{
        in = new FileInputStream(path);
        int len = 0;
        byte buffer[] = new byte[1024];
        out = response.getOutputStream();
        while((len = in.read(buffer)) > 0){
            out.write(buffer, 0, len);
        }
    }finally{
        if(in != null){
            try{
                in.close();
            }catch(Exception e){
                e.printStackTrace();
            }
        }
        if(out != null){
            try{
                out.close();
            }catch(Exception e){
                e.printStackTrace();
            }
        }
    }
}