ext 文件下载

//下载规则文件接口
function downloadTagRuleFile(fileName){
var url = '/tagrule?fileName=' + fileName;
Ext.Ajax.request({ //下载之前先判断一下文件存不存在;
url: url + "&checkFileExist=checkFileExist",
params: {checkFileExist: 'checkFileExist'},   //这样参数没有传过去
method: 'PUT',   //这里自己改，因为需要才写成这样的！
callback: function(op, suc, resp){
alert(resp.responseText);
if(suc){ //'success':false,'message':'file not found!'
var ret = eval("(" + resp.responseText + ")");
if(ret.success){
//下载文件;
var downloadForm = document.getElementById("tagRuleDownloadForm");
downloadForm.action = url;
    downloadForm.method = "POST";
    downloadForm.submit();
}else{
Ext.Msg.alert(TagRulerRes.TIP, ret.message);
}
}else{
Ext.Msg.alert(TagRulerRes.TIP, TagRulerRes.DOWNLOAD_FAILURE);
}
}
});
}

/**
     * 文件下载
     * 查看，修改规则时下载规则文件;
     */
    public void downloadFile(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException
    {
        response.setContentType("text/html");
        String fileName = request.getParameter("fileName");
        if(fileName == null || fileName.length() == 0)
        {
            log.info("文件不存在! fileName is null !");
            this.responseText("{'success':false,'message':'" +
                ResourceCfg.getResourceMessage(String.valueOf(ErrorCode.ADFILE_NOT_EXISTS)) + "'}", response);
            return ;
        }
       
        String checkFileExist = request.getParameter("checkFileExist");
        String svrFilePath = (MATRIX_BAK_DIRMATRIX_BAK_DIR + fileName).replace("\\", "/");
       
        File file = new File(svrFilePath);
        if (!file.exists())
        {
            log.info("文件不存在! path:" + file.getAbsolutePath());
            this.responseText("{'success':false,'message':'" +
                ResourceCfg.getResourceMessage(String.valueOf(ErrorCode.ADFILE_NOT_EXISTS)) + "'}", response);
        }
        else
        {  
            if (checkFileExist != null && checkFileExist.equals("checkFileExist"))
            {
                log.info("文件存在! path:" + file.getAbsolutePath());
                this.responseText("{'success':true,'message':''}", response);
            }
            else
            {  
                //写文件到网流;
                responseFile(response, fileName, svrFilePath);
            }
        }
    }