java 文件下载

文件下载的主要思路是前台触发form的post请求，后台将文件获取后写入输出流中。

1、前台定义form表单

<form id="downForm" method="post">
    <input type="hidden" id="filepath" name="filepath" value="">
    <input type="hidden" id="filename" name="filename" value="">
</form>

2、后台定义相关触发方法

function downForm(fileName,filePath){
    $("#downForm").attr("action","/demand/down");
    $("#filepath").val(filePath);
    $("#filename").val(fileName);
    $("#downForm").submit();
}

3、后台接收参数

public void down(HttpServletRequest request,HttpServletResponse response){
        request.setAttribute("filePath", request.getParameter("filepath"));
        request.setAttribute("fileName", request.getParameter("filename"));
        try {
            fileService.fileDownlaod(request,response, true);
        } catch (Exception e) {
            System.out.println(e.getMessage());
        }
    }

4、实现写入操作

　　

    public void fileDownlaod(HttpServletRequest request,HttpServletResponse response, boolean isOnLine) throws Exception{
        String filepath = (String) request.getAttribute("filePath");
        String filename = (String) request.getAttribute("fileName");
        File f = new File(filepath);
        if (!f.exists()) {
            throw new GlobalException("文件不存在");
        }
        response.reset(); // 非常重要
        if (isOnLine) { // 在线打开方式
            URL u = new URL("file:///" + filepath);
            response.setContentType(u.openConnection().getContentType());
            response.setHeader("Content-Disposition", "inline; filename=" + f.getName());
        } else { // 纯下载方式
            response.setContentType("application/x-msdownload");
            response.setHeader("Content-Disposition", "attachment; filename=" + new String(filename.getBytes("gb2312"), "iso-8859-1"));
        }
        OutputStream out = response.getOutputStream();
        BufferedInputStream br = new BufferedInputStream(new FileInputStream(f));
        byte[] buf = new byte[1024];
        int len = 0;
        while ((len = br.read(buf)) > 0){
            out.write(buf, 0, len);
        }
        br.close();
        out.close(); 
    }