ajax弹出状态值415错误

$.ajax({
    url: Common.base_url+"/account/getphonecode",
    data: JSON.stringify({ 'Mobile': mobile }),
    type: "POST",
    dataType: "json",
    contentType : 'application/json;charset=UTF-8',
    success: function (data) {
      /* 其他代码 */
    }
});

跨域操作下，以上代码一直报错：415 (Unsupported Media Type)

最后调试成功只因为一句代码

headers:{"Content-Type":"application/json;charset=UTF-8"},

$.ajax({
    url: Common.base_url+"/account/getphonecode",
    data: JSON.stringify({ 'Mobile': mobile }),
    type: "POST",
    dataType: "json",
    contentType : 'application/json;charset=UTF-8',
    headers:{"Content-Type":"application/json;charset=UTF-8"},
    success: function (data) {

    /* 其他代码 */

  }});