axios发送请求时springmvc无法接受参数

//设置全局的
axios.defaults.headers.post['Content-Type'] = 'application/x-www-form-urlencoded';
var instance = axios.create({}) // 这样创建出来的 只需要：
instance.defaults.headers.post['Content-Type'] = 'application/x-www-form-urlencoded';

var params = new URLSearchParams();
params.append("username", _this.username);
params.append("password", _this.password);
axios.post("/service/login", paramsOfJson
 ).then(function (response) {
 console.log(response);
 }).catch(function (error) {
 console.log(error);
 })

@PostMapping(value = "/login")
public String testLogin(@RequestBody Map dataMap)