Java实现文件点击没反应

Ext.Ajax.request({
url : '/yjy/training/TrainingTimeAction.do?method=downLoadAttchById',
params : {
timeId : timeids
},
success : function(response,options){
var result = Ext.util.JSON.decode(response.responseText);
Ext.Msg.alert("下载成功");
},
failure :function(response,options){
var result = Ext.util.JSON.decode(response.responseText);
Ext.Msg.alert("下载失败"+result.message);
}
});

后台action代码

String timeId = request.getParameter("timeId");
			String sql = "select doc_name from CPER.EHRTRAIN_item_DOCUMENT where item_id = ?";
			DbHelper dbHelper = new DbHelper();
			Object[] params = new Object[]{timeId};
			String fileName = (String)dbHelper.runSQLScalar(sql, params);
			String filePath = ServerPathUtil.getPathRoot()+"WEB-INF/cache/train_item_file/train_item_file_"+timeId+"/"+fileName;
	        File file = new File(filePath);
	        if(!file.exists()){
	        	logger.debug("文件不存在");
	        	throw new IOException("the file not exists");
	        }
	        response.setContentLength((int) file.length());
	        OutputStream o = response.getOutputStream();
	        byte b[] = new byte[5000];
	        //response.setContentType("application/x-msdownload");
	        response.setContentType("application/vnd.ms-excel");
	        response.setContentLength((int)file.length());
	        response.setHeader("Content-Disposition","attachment; filename="+fileName);
	        FileInputStream in = new FileInputStream(file);
	        int n;  
	        while ((n = in.read(b)) != -1) {
	            o.write(b, 0, n);
	        } 
	        in.close();
		}catch(Exception e){
			e.printStackTrace();
		}