/*js*/
<script type="text/javascript">
jQuery(document).ready(function () {
    $("a[ectype='clicknode']").click(function(){
        //后台查询ｕｒｌ地址的唯一标识，如记录ｉｄ
        var id = $(this).attr('name');
         //获取A标签下载地址,并在新标签页打开,并防止被浏览器阻止
        
        $.ajax({
                    url:"获取最终下载地址的ＵＲＬ请求地址,如：getlink.php",
                    data:"id="+id,
                    type:'post',
                    cache:false,
                    success:function(data){
                            var a = $("<a href='"+data+"' target='_blank' >test</a>").get(0);
                            var e = document.createEvent('MouseEvents');
                            e.initEvent('click', true, true);
                            a.dispatchEvent(e);
                    }
                    
        }); 
});
</script>

/*html*/
<a href="javascript:void(0);" ectype="clicknode">点击我获取下载地址，并打开</a>

/*
    getlink.php
    这里仅提供思路，下方实例为thinkphp中的代码。
*/
<?php
        $map['id'] = I('id');
        $seedurl = D('表名')->where($map)->getField('linkurl');
        echo $seedurl;
        exit;
?>