disposition

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在尽心web开发时，可能遇到以下几种需求：（disposition配置）
• 希望某类或者某已知MIME 类型的文件（比如：*.gif;*.txt;*.htm）能够在访问时弹出“文件下载”对话框。
• 希望客户端下载时以指定文件名显示。
• 希望某文件直接在浏览器上显示而不是弹出文件下载对话框。

对于上面的需求，使用Content-Disposition属性就可以解决。下面是代码示例：

response.setHeader("Content-disposition", "attachment;filename=" + fileName)。

//Content-disposition为属性名。

//attachment表示以附件方式下载。

如果要在页面中打开，则改为inline。

//filename如果为中文，则会出现乱码。解决办法有两种：

//1、使用fileName = new String(fileName.getBytes(), "ISO8859-1")语句

/* 验证content-disposition */
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        String path = this.getServletContext().getRealPath("/picture/桌面壁纸.jpg");
        String fileName = path.substring(path.indexOf("\\") + 1);
        //1、使用fileName = new String(fileName.getBytes(), "ISO8859-1")语句
        fileName = new String(fileName.getBytes(),"ISO8859-1");
        // response开始发送响应头
        response.setHeader("content-disposition", "attachment;filename="
                + fileName);

        // 基本的流操作
        OutputStream out = null;
        FileInputStream in = null;
        try {
            in = new FileInputStream(path);// 绝对路径
            out = response.getOutputStream();
            byte[] buf = new byte[1024];
            int len;
            while ((len = in.read(buf)) != -1) {
                out.write(buf, 0, len);
            }
        } finally {
            if (in != null) {
                try {
                    // 关闭流
                    in.close();
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
            if (out != null) {
                try {
                    // 关闭流
                    out.close();
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }

        }
    }

    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        doGet(request, response);
    }

//2、使用 URLEncoder.encode(fileName,"UTF-8" 语句

    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        String path = this.getServletContext().getRealPath(
                "/picture/桌面壁纸.jpg");
        String fileName = path.substring(path.lastIndexOf("\\") + 1);
        // System.out.println(fileName);//桌面壁纸.jpg
        /*response.setCharacterEncoding("UTF-8");
        response.setContentType("text/html;charset=UTF-8");*///这样是错误的
        // 发送响应头，如果文件是中文名，这要经过url编码
        response.setHeader("Content-disposition", "attachment;filename="
                + URLEncoder.encode(fileName,"UTF-8"));

        // 下载图片
        OutputStream out = null;
        FileInputStream in = null;
        try {
            in = new FileInputStream(path);// 绝对路径
            out = response.getOutputStream();
            byte[] buf = new byte[1024];
            int len;
            while ((len = in.read(buf)) != -1) {
                out.write(buf, 0, len);
            }
        } finally {
            if(in != null){
                try{
                    // 关闭流
                    in.close();
                }catch(Exception e){
                    e.printStackTrace();
                }
            }
            if(out != null){
                try{
                    // 关闭流
                    out.close();
                }catch(Exception e){
                    e.printStackTrace();
                }
            }

        }

    }

    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        doGet(request, response);
    }