java - gson反序列化: Reference owner of nested object

Question

我想为我的对象编写自定义反序列化器，但为了实现这一点，我需要访问反序列化对象的另一部分。想象一个像这样的 JSON 对象:

{
    "id": 2,
    "name": "circle",
    "dependencies": {
        "donut": "e8ed7bbd8715de2f5a85930912fcf238"
    },
    "someReference": {
        "type": "Model",
        "refersTo": "donut"
    }
}

我知道如何编写适配器/解串器。我也知道如何通过前者将“e8ed7bbd8715de2f5a85930912fcf238”变成 Java 对象。我不知道并且想知道的是如何将我的“ donut ”变成“e8ed7bbd8715de2f5a85930912fcf238”或“创建期间”的最终 Java 对象。此信息位于父级的字段中，因为“someReference”对应于另一个 Java 对象。所以顶级类是一个 Owner 字段:

public class Owner {
    public int id;

    public String name;

    public List<String, Resource> dependencies;

    public MyReference someReference;
}

id、name、dependencies 到目前为止一切正常。

那么:如何在反序列化过程中引用父对象呢？这可能吗？对于我正在尝试做的事情，有什么解决方法？

Answer 1

我写了一个反序列化器来做你想要的(当然如果我理解的话)。与您的要求唯一不同的是，我不知道您所说的 Reference 是什么意思，所以我改用了 String。但我认为您可以轻松调整我的代码。

我的所有者定义:

package stackoverflow.questions.q23718183;

import java.util.*;

public class Owner {
    public int id;

    public String name;

    public Map<String, String> dependencies;

    public MyReference someReference;

    @Override
    public String toString() {
        return "Owner [id=" + id + ", name=" + name + ", dependencies=" + dependencies + ", someReference=" + someReference + "]";
    }

    public static class MyReference {
        String type;
        String refersTo;

        @Override
        public String toString() {
            return "MyReference [type=" + type + ", refersTo=" + refersTo + "]";
        }

    }

}

我的反序列化器:

package stackoverflow.questions.q23718183;

import java.io.IOException;
import java.lang.reflect.Type;
import java.util.*;

import com.google.gson.*;
import com.google.gson.stream.*;
import com.google.gson.reflect.TypeToken;

public class OwnerDeserializer implements JsonDeserializer<Owner> {

    @Override
    public Owner deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) throws JsonParseException {
        if (json == null)
            return null;
        else {
            Owner owner = new Owner();
            JsonObject jo = json.getAsJsonObject();

            owner.id = jo.get("id").getAsInt();
            owner.name = jo.get("name").getAsString();

            TypeToken<Map<String, String>> mapType = new TypeToken<Map<String, String>>() {};
            owner.dependencies = context.deserialize(jo.get("dependencies"), mapType.getType());

            Owner.MyReference reference = new Owner.MyReference();
            JsonObject jo2 = jo.get("someReference").getAsJsonObject();
            reference.type = jo2.get("type").getAsString();
            reference.refersTo = owner.dependencies.get(jo2.get("refersTo").getAsString());

            owner.someReference = reference;

            return owner;
        }
    }
}

我的测试代码:

package stackoverflow.questions.q23718183;

import com.google.gson.*;

public class Q23718183 {

    public static void main(String[] args) {
        String s = " {                                                          "+
                "    \"id\": 2,                                                 "+
                "    \"name\": \"circle\",                                      "+
                "    \"dependencies\": {                                        "+
                "        \"donut\": \"e8ed7bbd8715de2f5a85930912fcf238\"        "+
                "    },                                                         "+
                "    \"someReference\": {                                       "+
                "        \"type\": \"Model\",                                   "+
                "        \"refersTo\": \"donut\"                                "+
                "    } "+
                "}";

        GsonBuilder b = new GsonBuilder();
        b.registerTypeAdapter(Owner.class, new OwnerDeserializer());
        Gson g = b.create();

        Owner o = g.fromJson(s, Owner.class);

        System.out.println(o);


    }

}

这是结果:

Owner [id=2, name=circle, dependencies={donut=e8ed7bbd8715de2f5a85930912fcf238}, someReference=MyReference [type=Model, refersTo=e8ed7bbd8715de2f5a85930912fcf238]]

如您所见，donut 被其值替换为 dependencies 节点。