java - 如何修复 "Expected BEGIN_OBJECT but was BEGIN_ARRAY"？

Question

我正在使用 Retrofit 2 发送 HTTP 请求，我已经定期完成了所有操作，但是，情况“不标准”。我有一个问题，响应类中要接收的对象之一曾经作为对象发送，而另一个作为列表发送。所以我不知道是在响应类中将其初始化为对象还是数组。

Here is my full JSON response:

{
    "data": [
        {
            "name": "John",
            "surname": "Smith",
            "nicname": "Joe",
            "age": "32",
            "description": "Example",
            "state": "Nevada",
            "city": "Las Vegas",
            "job": "Security",
            "adress": "Some adress 1",
            "postcode": "412421",
            "details": {
                "intro": {
                    "title": "Mr.",
                      "married": "No",
                    "children": "2"
                },
                "rest": {
                    "pitctures":"24",
                    "chats": "7",
                    "lastChat": "12-01-2016",
                    "lastVisited": "07-04-2017",
                }
            }
        },
        {
            "name": "John",
            "surname": "Smith",
            "nicname": "Joe",
            "age": "32",
            "description": "Example",
            "state": "Nevada",
            "city": "Las Vegas",
            "job": "Security",
            "adress": "Some adress 1",
            "postcode": "412421",
            "details": {
                "intro": {
                    "title": "Mr.",
                      "married": "No",
                    "children": "No"
                },
                "rest": []
            }
        }
    ],
    "errors": false,
    "update_notifications": {
        "message": [],
        "friend_request": [],
        "code": "IzS0hivN1cyHBdygpeWv"
    }
}

Details.java class:

public class Details {

    @SerializedName("intro")
    @Expose
    private Intro intro;
    @SerializedName("rest")
    @Expose
    private Rest restObject;

    private ArrayList<Rest> restList;

    public Details(Intro intro, Rest restObject) {
        this.intro = intro;
        this.restObject = restObject;
    }

    public Details(Intro intro, ArrayList<Rest> restList) {
        this.intro = intro;
        this.restList = restList;
    }

    public Intro getIntro() {
        return intro;
    }

    public void setIntro(Intro intro) {
        this.intro = intro;
    }

    public Rest getRestObject() {
        return restObject;
    }

    public void setRestObject(Rest restObject) {
        this.restObject = restObject;
    }

    public ArrayList<Rest> getRestList() {
        return restList;
    }

    public void setRestList(ArrayList<Rest> restList) {
        this.restList = restList;
    }
}

And here is my CustomDeserializer.java (rest array neeed to be empty, maybe that's a problem) based on @Farid's answer:

public class CustomDeserializer implements JsonDeserializer<Details> {

    @Override
    public Details deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) throws JsonParseException {

        JsonObject detailsObject = json.getAsJsonObject().get("details").getAsJsonObject();
        Details details;

        JsonObject introObject = detailsObject.get("intro").getAsJsonObject();
        String title = introObject.get("title").getAsString();
        String married = introObject.get("married").getAsString();
        String children = introObject.get("children").getAsString();

        try {
            JsonObject restObject = detailsObject.get("rest").getAsJsonObject();

            String pitctures = restObject.get("pitctures ").getAsString();
            String chats = restObject.get("chats ").getAsString();
            String lastChat = restObject.get("lastChat ").getAsString();
            String lastVisited = restObject.get("lastVisited ").getAsString();

            details = new Details(new Intro(title, married, children),
                      new Rest(pitctures, chats, lastChat, lastVisited));
        }catch (IllegalStateException e){
            JsonArray restArray = detailsObject.get("rest").getAsJsonArray();
            ArrayList<Rest> restList = new ArrayList<>();
            details = new Details(new Intro(title, married, children), restList);
        }
        return details;
    }
}

In MainActivity based on @Farid's answer:

Gson gsonConverter = new GsonBuilder().registerTypeAdapter(Details.class, new CustomDeserializer()).create();


        Retrofit retrofit = new Retrofit.Builder()
                .baseUrl(myUrl)
                .addConverterFactory(GsonConverterFactory.create(gsonConverter))
                .build();

        service1 = retrofit.create(MyAPI.class);

        final ProgressDialog progressDialog = new ProgressDialog(this);
        progressDialog.setCancelable(false);
        progressDialog.setMessage("Please wait!");
        progressDialog.show();

        final MyRequest myRequest = new MyRequest();

        myRequest.setPin(pin);

        final Call<MyResponse> myResponseCall = service1.get (code, myRequest);

        myResponseCall.enqueue(new Callback<MyResponse>() {
                @Override
                public void onResponse(Call<MyResponse> call, Response<MyResponse> response) {
                }
            });

Answer 1

这是可能的。您必须创建一个自定义反序列化器。如您所见，有 JsonDeserializer<Details>其类型参数为Details这意味着任何时候 GSON 尝试反序列化 Details对象，它会调用CustomDeserializer反序列化它。里面有什么Details对象应该手动反序列化，如 CustomDeserializer 中所示。类，而 Details 之外的所有其他类型类(例如 Class、String、int)将由 GSON 无缝处理

CustomDeserializer.java

    public class CustomDeserializer implements JsonDeserializer<Details> {

    @Override
    public Details deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) throws JsonParseException {

        JsonObject detailsObject = json.getAsJsonObject();
        Details details;
        Intro intro = new Intro(detailsObject.get("intro").getAsJsonObject().get("example").getAsString());

        try {
            JsonObject restObject = detailsObject.get("rest").getAsJsonObject();
            String example = restObject.get("example").getAsString();

            details = new Details(intro, new Rest(example));
        }catch (IllegalStateException e){ // In case rest is ArrayList
            JsonArray restArray = detailsObject.get("rest").getAsJsonArray();
            ArrayList<Rest> resList = new ArrayList<>();
            for (JsonElement element: restArray){
                JsonObject restObject = element.getAsJsonObject();
                String example = restObject.get("example").getAsString();
                resList.add(new Rest(example));
            }

            details = new Details(intro, resList);
        }

        return details;
    }
}

那么你必须注册CustomDeserializer如TypeAdapter如下:

 Gson gsonConverter = GsonBuilder().registerTypeAdapter(Details::class.java,
 CustomDeserializer()).create();

 Retrofit retrofit = new Retrofit.Builder()
 .addConverterFactory(GsonConverterFactory.create(gsonConverter))
 ///Rest of Retrofit builder code

如果您想了解有关自定义反序列化的更多信息，请搜索“gson 反序列化”并找到最吸引您的教程。

<小时/>

下面的代码 fragment 是OP特定的类

Response.java

public class Response {

    private List<DataItem> data = null;
    private Boolean errors;
    private String example;

    public List<DataItem> getData() {
        return data;
    }

    public void setData(List<DataItem> data) {
        this.data = data;
    }

    public Boolean getErrors() {
        return errors;
    }

    public void setErrors(Boolean errors) {
        this.errors = errors;
    }

    public String getExample() {
        return example;
    }

    public void setExample(String example) {
        this.example = example;
    }

}

Data.java

 public class DataItem { 
    private String example;
    private Details details;

    public String getExample() {
        return example;
    }

    public void setExample(String example) {
        this.example = example;
    }

    public Details getDetails() {
        return details;
    }

    public void setDetails(Details details) {
        this.details = details;
    }
}

Details.java

public class Details {

    private Intro intro;
    private Rest restObject;
    private ArrayList<Rest> restList;

    public Details(Intro intro, ArrayList<Rest> restList) {
        this.intro = intro;
        this.restList = restList;
    }

    public Details(Intro intro, Rest restObject) {
        this.intro = intro;
        this.restObject = restObject;
    }

    public Rest getRestObject() {
        return restObject;
    }

    public ArrayList<Rest> getRestList() {
        return restList;
    }

    public Intro getIntro() {
        return intro;
    }

    public void setIntro(Intro intro) {
        this.intro = intro;
    }
}

Intro.java

public class Intro {

    public Intro(String example) {
        this.example = example;
    }

    private String example;

    public String getExample() {
        return example;
    }

    public void setExample(String example) {
        this.example = example;
    }

}

Rest.java

public class Rest {
    private String example;

    public Rest(String example) {
        this.example = example;
    }

    public String getExample() {
        return example;
    }
}