如何在Flutter应用程序中从JWT获得索赔

JWT令牌只是base64编码的JSON字符串（其中3个，由点分隔）：

import 'dart:convert';Map<String, dynamic> parseJwt(String token) {  final parts = token.split('.');  if (parts.length != 3) {    throw Exception('invalid token');  }  final payload = _deprebase64(parts[1]);  final payloadMap = json.depre(payload);  if (payloadMap is! Map<String, dynamic>) {    throw Exception('invalid payload');  }  return payloadMap;}String _deprebase64(String str) {  String output = str.replaceAll('-', '+').replaceAll('_', '/');  switch (output.length % 4) {    case 0:      break;    case 2:      output += '==';      break;    case 3:      output += '=';      break;    default:      throw Exception('Illegal base64url string!"');  }  return utf8.depre(base64Url.depre(output));}