未捕获的TypeError：无法读取未定义的属性toLowerCase

Question

如何使用jQuery和spring security在所有Ajax请求中包含令牌？

目前我收到以下错误

  

未捕获的TypeError：无法读取属性＆＃39; toLowerCase＆＃39;未定义的

使用Javascript：

function editUser(data) {

var token = $("meta[name='_csrf']").attr("content");
var header = $("meta[name='_csrf_header']").attr("content");
var ctx = location.href.substring(0, location.href.lastIndexOf("/"));
var dataObject = JSON.stringify({ 'username': data });

$.ajax({
      url: ctx+'/users/edit',
      type: 'POST',
      beforeSend: function(xhr){
          xhr.setRequestHeader(header, token);
      },
      data: data
    });
}   

控制器：

@RequestMapping(value = "/users/edit", method = RequestMethod.POST)
public String editUser(@RequestParam("username") String username) {

    System.out.println(username);
    return "users/edit";
}

toLowerCase函数在jQuery中

// Caches the header
                setRequestHeader: function( name, value ) {
                    var lname = name.toLowerCase();
                    if ( !state ) {
                        name = requestHeadersNames[ lname ] = requestHeadersNames[ lname ] || name;
                        requestHeaders[ name ] = value;
                    }
                    return this;
                },

Answer 1

要么确保页面始终包含<meta name="_csrf" content="something">和<meta name="_csrf_header" content="something">标记，要么在尝试设置标题之前让AJAX代码检查值是否存在：

beforeSend: function(xhr) {
    if (header && token) {
        xhr.setRequestHeader(header, token);
    }
}