获取嵌套的JSON对象使用改造GSON [英] Get nested JSON object with GSON using retrofit

问题描述

我消费从我的Andr​​oid应用程序的API，所有的JSON的反应是这样的：

I'm consuming an API from my android app, and all the JSON responses are like this:

{
    'status': 'OK',
    'reason': 'Everything was fine',
    'content': {
         < some data here >
}

现在的问题是，我所有的POJO有状态，的原因字段，在<$ C $一个C>内容字段是真正的POJO我想要的。

The problem is that all my POJOs have a status, reason fields, and inside the content field is the real POJO I want.

有什么办法创造GSON的自定义转换总是提取内容字段，所以改造返回此时，相应的POJO？

Is there any way to create a custom converter of Gson to extract always the content field, so retrofit returns the appropiate POJO?

推荐答案

您可以编写一个自定义解串器，返回嵌入对象。

You would write a custom deserializer that returns the embedded object.

比方说，你的JSON是：

Let's say your JSON is:

{
    "status":"OK",
    "reason":"some reason",
    "content" : 
    {
        "foo": 123,
        "bar": "some value"
    }
}

您会再有一个内容 POJO：

You'd then have a Content POJO:

class Content
{
    public int foo;
    public String bar;
}

然后你写一个解串器：

Then you write a deserializer:

class MyDeserializer implements JsonDeserializer<Content>
{
    @Override
    public Content deserialize(JsonElement je, Type type, JsonDeserializationContext jdc)
        throws JsonParseException
    {
        // Get the "content" element from the parsed JSON
        JsonElement content = je.getAsJsonObject().get("content");

        // Deserialize it. You use a new instance of Gson to avoid infinite recursion
        // to this deserializer
        return new Gson().fromJson(content, Content.class);

    }
}

现在，如果你建立一个 GSON 与 GsonBuilder 并注册解串器：

Now if you construct a Gson with GsonBuilder and register the deserializer:

Gson gson = 
    new GsonBuilder()
        .registerTypeAdapter(Content.class, new MyDeserializer())
        .create();

您可以直接反序列化的JSON到你的内容：

You can deserialize your JSON straight to your Content:

Content c = gson.fromJson(myJson, Content.class);

修改，从添加注释：

如果您有不同类型的消息，但他们都有内容区域，就可以使解串器通用这样做：

If you have different types of messages but they all have the "content" field, you can make the Deserializer generic by doing:

class MyDeserializer<T> implements JsonDeserializer<T>
{
    @Override
    public T deserialize(JsonElement je, Type type, JsonDeserializationContext jdc)
        throws JsonParseException
    {
        // Get the "content" element from the parsed JSON
        JsonElement content = je.getAsJsonObject().get("content");

        // Deserialize it. You use a new instance of Gson to avoid infinite recursion
        // to this deserializer
        return new Gson().fromJson(content, type);

    }
}

您只需要注册一个实例，为每个类型的：

You just have to register an instance for each of your types:

Gson gson = 
    new GsonBuilder()
        .registerTypeAdapter(Content.class, new MyDeserializer<Content>())
        .registerTypeAdapter(DiffContent.class, new MyDeserializer<DiffContent>())
        .create();

当你调用 .fromJson（）类型带入解串器，所以它应该再适用于所有的类型。

When you call .fromJson() the type is carried into the deserializer, so it should then work for all your types.

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