发布到我的 Django API 时：errorcom.google.gson.JsonParseException: 无法解析 json

Question

谁能告诉我我在这篇文章中做错了什么？

我怀疑我错误地发布到我的 django API。我基本上有一个 Question 对象，其中包含一个 Answers 数组的字段。我可以在没有答案的情况下正确发布，但是当我尝试为 answers 添加 JsonArray 时，发布失败并出现无法解析错误。

LogCat 摘录

05-21 00:12:52.875  15720-15720/com.pipit.waffle D/ConnectToBackend﹕ {"text":"gf or ed","answers":[{"text":"gf","votes":0,"id":null},{"text":"ed","votes":0,"id":null}],"user_id":"temp user id"}
05-21 00:12:52.875  15720-15720/com.pipit.waffle D/ConnectToBackend﹕ postQuestion called with {MY API} and has errorcom.google.gson.JsonParseException: unable to parse json
05-21 00:12:52.875  15720-15720/com.pipit.waffle D/ConnectToBackend﹕ postQuestion returns result with NULL

Django 端

序列化器.py

class EmbeddedAnswerSerializer(serializers.ModelSerializer):
    votes = serializers.IntegerField(read_only=True)
    picture = serializers.ImageField(read_only=True)
    class Meta:
        model = Answer
        fields = ('id', 'picture', 'text', 'votes',)


class QuestionSerializer(serializers.ModelSerializer):
    answers = EmbeddedAnswerSerializer(many=True, source='answer_set')

    class Meta:
        model = Question
        fields = ('id', 'answers', 'created_at', 'text', 'user_id',)


class AnswerSerializer(serializers.ModelSerializer):
    text = serializers.CharField(read_only=True)
    vote = serializers.BooleanField(required=True)
    picture = serializers.ImageField(read_only=True)
    votes = serializers.IntegerField(read_only=True)

models.py

class Question(models.Model):
    user_id = models.CharField(max_length=36)
    text = models.CharField(max_length=140)
    created_at = models.DateTimeField(auto_now_add=True)

    def __unicode__(self):
        return u'Question #{}'.format(self.pk)

class Answer(models.Model):
    picture = models.ImageField(("Picture"), upload_to=upload_pic_to, blank=True)
    question = models.ForeignKey(Question)
    text = models.CharField(max_length=25)
    votes = models.IntegerField(default=0)

    def __unicode__(self):
        return u'Answer to question {} ({} votes)'.format(self.question_id, self.votes)

客户端 (安卓)

public static void postQuestion(final Context mcontext, Question mquestion){
        JsonArray answerarray = new JsonArray();
        JsonObject answerjson = new JsonObject();
        JsonObject answerjson2 = new JsonObject();
        answerjson.addProperty("text", mquestion.getChoices().get(0).getAnswerBody());
        answerjson2.addProperty("text", mquestion.getChoices().get(1).getAnswerBody());
        answerjson.addProperty("votes", 0);
        answerjson2.addProperty("votes", 0);
        answerjson.addProperty("id", mquestion.getId());
        answerjson2.addProperty("id", mquestion.getId());
        answerarray.add(answerjson);
        answerarray.add(answerjson2);

        JsonObject json = new JsonObject();
        json.addProperty("text", mquestion.getQuestionBody());
        json.add("answers", answerarray);
        json.addProperty("user_id", "temp user id");
        final String url = "my endpoint";
        Ion.with(mcontext) //Ion Koush is just a library for making async android requests to a URL  - doubt this is the problem
                .load(url)
                .setJsonObjectBody(json)
                .asJsonObject()
                .setCallback(new FutureCallback<JsonObject>() {
                    @Override
                    public void onCompleted(Exception e, JsonObject result) {
                        if (e != null){
                            Log.d("ConnectToBackend", "postQuestion called with "+url+" and has error" + e.toString());
                            if (result==null){
                                Log.d("ConnectToBackend", "postQuestion returns result with NULL");
                            }
                        }
                        else{
                            //Do Stuff
                        }

                    }
                });
    }

这是一个成功 GET 到同一端点的示例

{"id":5,"answers":[{"id":10,"picture":"someurl","text":"microsoft","votes":0},{"id":9,"picture":"someurl","text":"apple","votes":0}],"created_at":"2015-03-15T04:14:00.782903Z","text":"MicroSoft or Apple","user_id":"8"}

Answer 1

你确定它实际上不是一个成功的字符串而不是字典吗？我在Django端遇到过这个问题，对Android了解不多。

使用 python 会是：

import json
your_dict = {...}

# this stringifies the dict
json.dumps(your_dict)

我知道您正在客户端上执行此操作，因此上面的代码不会是您的答案，但这是一个想法，希望对您有所帮助！

Answer 2

您可以通过更改 QuestionSerializer 以另一种方式尝试：

class QuestionSerializer(serializers.ModelSerializer):
    answers = serializers.SerializerMethodField()

    class Meta:
        model = Question
        fields = ('id', 'answers', 'created_at', 'text', 'user_id',)

    def get_answers(self,obj):
        ans_set = AnswerSerializer(Answer.objects.filter(question=obj),many=True)
        return ans_set

Answer 3

我认为该服务的数据格式不正确......

{"text":"gf or ed","answers":[{"text":"gf","votes":0,"id":null},{"text":"ed","votes":0,"id":null}],"user_id":"temp user id"}

'Picture' 不存在，你不是从 android 发送的......而且 Django 默认将字段设置为'required'，所以它应该会导致你的问题......

你有任何来自 python 的踪迹吗？尝试调试它。

Answer 4

您在这里缺少您的 views.py 代码，但我猜您正在使用 ListCreateAPIView 开箱即用。事实证明，django rest 框架不支持自动创建开箱即用的嵌套对象，因此您需要添加自己的代码来解决该功能。这里有很好的文档：

http://www.django-rest-framework.org/api-guide/serializers/#writable-nested-representations