java - 无法获取格式正确的 json 对象

Question

假设我从 api 获取一些 json 数组，如下

[{"id":1,"title":"title","description":"description","vote":null,"created_at":"2013-11-12T21:08:10.922Z","updated_at":"2013-11-12T21:08:10.922Z"}]

我想从 URL_Some 网址检索此 json 作为 Some 对象

public class Some implements Serializable {

    private String id;
    private String title;
    private String description;
    private String vote;
    private String created_at;
    private String updated_at;
    }//with all getters and setters

.

public List<Some> getSome() throws IOException {
        try {
            HttpRequest request = execute(HttpRequest.get(URL_Some));
            SomeWrapper response = fromJson(request, SomeWrapper.class);
            Field[] fields = response.getClass().getDeclaredFields();
            for (int i=0; i<fields.length; i++)
            {
                try {
                    Log.i("TAG", (String) fields[i].get(response));
                } catch (IllegalAccessException e) {
                    e.printStackTrace();  //To change body of catch statement use File | Settings | File Templates.
                }
                Log.i("TAG", fields[i].getName());
            }
            if (response != null && response.results != null)
                return response.results;
            return Collections.emptyList();
        } catch (HttpRequestException e) {
            throw e.getCause();
        }
    }

和SomeWrapper只是

private static class SomeWrapper {

        private List<Some> results;
    }

问题是我不断收到此消息

java.lang.IllegalStateException: Expected BEGIN_OBJECT but was BEGIN_ARRAY

PS:我用

import com.google.gson.Gson;

import com.google.gson.GsonBuilder;

import com.google.gson.JsonParseException;

Answer 1

你的 json 实际上应该是这样的:

{"results": [{"id":1,"title":"title","description":"description","vote":null,"created_at":"2013-11-12T21:08:10.922Z","updated_at":"2013-11-12T21:08:10.922Z"}]}

Gson 将尝试解析 json 并创建一个 SomeWrapper 对象。仅此一点就告诉 Gson 他将等待这种格式的 json {...}因为他在等待一个物体。然而，您传递了一个数组，这就是为什么它提示期望 BEGIN_OBJECT ( { ) 但得到 BEGIN_ARRAY 而不是 ( [ )。之后，它会期望这个 json 对象有一个 results字段，它将保存一个对象数组。

您可以创建List<Some>然而，无需包装类即可直接使用。为此，请执行以下操作:

Type type= new TypeToken<List<Some>>() {}.getType();
List<Some> someList = new GsonBuilder().create().fromJson(jsonArray, type);

在这种情况下，您可以使用您发布的原始 json 数组。