我是 Flutter/Dart、Go 和移动开发的新手。我目前正在用 flutter 编写一个登录身份验证页面，该页面连接到用 go 编写的后端。为了检查是否一切正常，我想打印出后端在控制台中发回的 cookie。不幸的是，我收到错误消息，不知道该怎么做。

编辑:我已经能够读取 cookie，我应该以“session=UUID”这种格式保存 cookie 还是只保存“UUID”？我想将此 cookie 发回 header 中以供将来获取请求。我的 Go 代码将检查 cookie 名称“session”，但我不确定以该格式发回它是否正确。

Flutter 代码(我在另一个 stackoverflow 帖子上读到在使用 android 模拟器时使用 10.0.2.2 作为本地主机):

编辑:玩弄代码后，我能够读取 header 中的 cookie，但它也有名称，而不仅仅是 UUID。

import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;
import 'dart:convert';



class Login extends StatefulWidget {
  @override
  State<StatefulWidget> createState(){
    return new LoginState();
  }
}


class LoginState extends State <Login> {

  final formKey = GlobalKey<FormState>();
  String _email, _password;
  String cookie;



  void loginApi(){
    var form = formKey.currentState;
    var url = "http://10.0.2.2:8080";
      if (form.validate()) {
        form.save();
        var body = { "Email":_email, "Pass":_password};
        http.post(url,body:json.encode(body)).then((response){
          print(response.headers['set-cookie']);
        });
      }
  }

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(
        title: new Text("Login"),
        backgroundColor: Colors.white,
      ),
      body: new Container(
        alignment: Alignment.center,
        child: Form(
            key: formKey,
            child: Column(
              children: <Widget>[

                TextFormField(
                  autocorrect: false,
                  decoration: InputDecoration(
                    labelText: "Email:",
                  ),
                  validator: (str) =>
                  !str.contains('@') ? "Not a Valid Email!" : null,
                  onSaved: (str) =>  _email = str,
                ),

                TextFormField(
                  autocorrect: false,
                  decoration: InputDecoration(
                    labelText: "Password:",
                  ),
                  validator: (str) =>
                  str.length <= 7 ? "Not a Valid Password!" : null,
                  onSaved: (str) => _password = str,
                  obscureText: false,
                ),

                RaisedButton(
                  child: Text("Submit"),
                  onPressed:loginApi,
                ),
              ],
            )
        ),
      ),


    );
  }
}

Golang 代码(编辑:在 panic 错误后插入一个缺少的大括号并删除代码末尾的大括号):

package main

import (
    "encoding/json"
    "html/template"
    "net/http"

    uuid "github.com/satori/go.uuid"
    "golang.org/x/crypto/bcrypt"
)

type user struct {
    UserName string //Same as email
    Password []byte
}

type logindata struct {
    Email string
    Pass  string
}

var tpl *template.Template
var dbUsers = map[string]user{}
var dbSess = map[string]string{}

func init() {
    bs, _ := bcrypt.GenerateFromPassword([]byte("password"), bcrypt.MinCost)
    dbUsers["test@test.com"] = user{"test@test.com", bs}
}

func main() {
    http.HandleFunc("/", login)
    http.Handle("/favicon.ico", http.NotFoundHandler()) //Don't have favicon
    http.ListenAndServe(":8080", nil)
}

func login(w http.ResponseWriter, req *http.Request) {
    var data logindata

    decoder := json.NewDecoder(req.Body)
    err_decode := decoder.Decode(&data)
    if err_decode != nil {
        panic(err_decode)
    }
    u, ok := dbUsers[data.Email]
    if !ok {
        http.Error(w, "Username and/or password do not match", http.StatusForbidden)
        return
    }

    err_compare := bcrypt.CompareHashAndPassword(u.Password, []byte(data.Pass))
    if err_compare != nil {
        http.Error(w, "Username and/or password do not match", http.StatusForbidden)
        return
    }

    // create session
    sID, _ := uuid.NewV4()
    c := &http.Cookie{
        Name:  "session",
        Value: sID.String(),
    }
    http.SetCookie(w, c)
    dbSess[c.Value] = data.Email
    return

}

Flutter 代码的控制台输出(在我输入用户名和密码并单击提交后，用户名是“test@test.com”密码是“password”):

Performing hot reload...
Reloaded 0 of 489 libraries in 544ms.
I/flutter ( 3778): session=db3690d6-db6e-4658-8b5b-5f2d3f908a65

我还在我的浏览器上访问了 localhost:8080，希望显示一个空白页面，但它显示“页面不工作”，我的终端输出了以下错误，我猜是因为我正在使用浏览器访问它，但我没有' 发送 JSON 数据，不确定:

2018/05/24 23:29:38 http: panic serving [::1]:40010: EOF
goroutine 6 [running]:
net/http.(*conn).serve.func1(0xc82001a280)
    /usr/lib/go-1.6/src/net/http/server.go:1389 +0xc1
panic(0x76c6c0, 0xc82000a160)
    /usr/lib/go-1.6/src/runtime/panic.go:443 +0x4e9
main.login(0x7f96c9a848b8, 0xc82012c000, 0xc8201121c0)
    /home/daniel/Desktop/Workspace/Genesis/main.go:43 +0x176
net/http.HandlerFunc.ServeHTTP(0x8a8688, 0x7f96c9a848b8, 0xc82012c000, 0xc8201121c0)
    /usr/lib/go-1.6/src/net/http/server.go:1618 +0x3a
net/http.(*ServeMux).ServeHTTP(0xc820013020, 0x7f96c9a848b8, 0xc82012c000, 0xc8201121c0)
    /usr/lib/go-1.6/src/net/http/server.go:1910 +0x17d
net/http.serverHandler.ServeHTTP(0xc82001a100, 0x7f96c9a848b8, 0xc82012c000, 0xc8201121c0)
    /usr/lib/go-1.6/src/net/http/server.go:2081 +0x19e
net/http.(*conn).serve(0xc82001a280)
    /usr/lib/go-1.6/src/net/http/server.go:1472 +0xf2e
created by net/http.(*Server).Serve
    /usr/lib/go-1.6/src/net/http/server.go:2137 +0x44e
2018/05/24 23:29:38 http: panic serving [::1]:40012: EOF
goroutine 18 [running]:
net/http.(*conn).serve.func1(0xc82011c080)
    /usr/lib/go-1.6/src/net/http/server.go:1389 +0xc1
panic(0x76c6c0, 0xc82000a160)
    /usr/lib/go-1.6/src/runtime/panic.go:443 +0x4e9
main.login(0x7f96c9a848b8, 0xc8201161a0, 0xc820154000)
    /home/daniel/Desktop/Workspace/Genesis/main.go:43 +0x176
net/http.HandlerFunc.ServeHTTP(0x8a8688, 0x7f96c9a848b8, 0xc8201161a0, 0xc820154000)
    /usr/lib/go-1.6/src/net/http/server.go:1618 +0x3a
net/http.(*ServeMux).ServeHTTP(0xc820013020, 0x7f96c9a848b8, 0xc8201161a0, 0xc820154000)
    /usr/lib/go-1.6/src/net/http/server.go:1910 +0x17d
net/http.serverHandler.ServeHTTP(0xc82001a100, 0x7f96c9a848b8, 0xc8201161a0, 0xc820154000)
    /usr/lib/go-1.6/src/net/http/server.go:2081 +0x19e
net/http.(*conn).serve(0xc82011c080)
    /usr/lib/go-1.6/src/net/http/server.go:1472 +0xf2e
created by net/http.(*Server).Serve
    /usr/lib/go-1.6/src/net/http/server.go:2137 +0x44e
2018/05/24 23:29:43 http: panic serving [::1]:40016: EOF
goroutine 7 [running]:
net/http.(*conn).serve.func1(0xc82001a380)
    /usr/lib/go-1.6/src/net/http/server.go:1389 +0xc1
panic(0x76c6c0, 0xc82000a160)
    /usr/lib/go-1.6/src/runtime/panic.go:443 +0x4e9
main.login(0x7f96c9a848b8, 0xc82012c1a0, 0xc8201122a0)
    /home/daniel/Desktop/Workspace/Genesis/main.go:43 +0x176
net/http.HandlerFunc.ServeHTTP(0x8a8688, 0x7f96c9a848b8, 0xc82012c1a0, 0xc8201122a0)
    /usr/lib/go-1.6/src/net/http/server.go:1618 +0x3a
net/http.(*ServeMux).ServeHTTP(0xc820013020, 0x7f96c9a848b8, 0xc82012c1a0, 0xc8201122a0)
    /usr/lib/go-1.6/src/net/http/server.go:1910 +0x17d
net/http.serverHandler.ServeHTTP(0xc82001a100, 0x7f96c9a848b8, 0xc82012c1a0, 0xc8201122a0)
    /usr/lib/go-1.6/src/net/http/server.go:2081 +0x19e
net/http.(*conn).serve(0xc82001a380)
    /usr/lib/go-1.6/src/net/http/server.go:1472 +0xf2e
created by net/http.(*Server).Serve
    /usr/lib/go-1.6/src/net/http/server.go:2137 +0x44e

最佳答案

在你的代码中

    http.post(url,body:json.encode(body)).then((http.Response response){
      cookie = response.headers['session'];
    });
    debugPrint(cookie);

这条线

debugPrint(cookie);

之前执行

cookie = response.headers['session'];

因此当您打印它时，预计 cookie 为 null。出于某些奇怪的原因，debugPrint(null) 抛出了一个关于“slit on null”的异常

试试看

    http.post(url,body:json.encode(body)).then((http.Response response){
      cookie = response.headers['session'];
      debugPrint(cookie);   
    });

关于post - 带有 Go 后端的 Flutter/Dart 前端中的发布请求问题，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/50516777/