使用Gson自定义反序列化成地图 [英] Custom deserialization into a Map using Gson

问题描述

我有以下JSON：

{
    "abc": {
        "linkedTo": "count",
        // possibly more data...
    },
    "plmtq": {
        "linkedTo": "title",
        "decode": "true",
        // possibly more data...
    }
}

我需要将这个JSON加载到一个 Map< String，Holder> 中，并带有abc和plmtq。

以下是我的持有人类：

I need to load this JSON into a Map<String, Holder>, with keys "abc" and "plmtq".
Below is my Holder class:

public class Holder {
  private final Map<String, String> data;

  public Holder(Map<String, String> data) {
    this.data = data;
  }

  // More methods in this class...
}

JSON不符合我的类结构，但我不能更改JSON或类。

我需要的是一种自定义反序列化的方法所以我可以将JSON解析成一个 Map< String，Holder> 。

有没有办法这样做？

The JSON does not match my class structure, but I cannot change the JSON or the classes.
What I need is a way to customize the deserialization so I can parse the JSON into a Map<String, Holder>.
Is there any way to do this?

下面是代码，但它看起来太复杂，必须有一个更简单的方法来实现...

Below is the code which does that, but it looks too complex and there must be a simpler way to do it...

private static Map<String, Holder> getMap(String jsonLine)
{
    Map<String, Holder> holder = new HashMap<>();
    JsonElement jelement = new JsonParser().parse(jsonLine);
    JsonObject jobject = jelement.getAsJsonObject();

    for (Map.Entry<String, JsonElement> entry : jobject.entrySet())
    {
        Map<String, String> metadata = new HashMap<>();
        JsonObject element = entry.getValue().getAsJsonObject();

        for (Map.Entry<String, JsonElement> entry2 : element.entrySet())
        {
            metadata.put(entry2.getKey(), entry2.getValue().getAsString());
        }

        holder.put(entry.getKey(), new Holder(metadata));
    }
    return holder;
}

推荐答案

如果你真的需要保持您的持有者类，我唯一​​可以想到的是为您的持有者创建一个自定义解串器 class。

If you really need to keep your Holder class as is, the only option I can think of is to create a custom deserializer for your Holder class.

通过这样做，每当你告诉Gson将一些JSON解析成一个 Holder 对象，它将使用您的解串器，而不是通常的方式（即将JSON键映射到对象属性）。

By doing this, whenever you tell Gson to parse some JSON into a Holder object, it will use your deserializer, instead of doing it 'the normal way' (i.e., mapping JSON keys to object properties).

这样的东西：

private class HolderDeserializer implements JsonDeserializer<Holder> {

  @Override
  public Holder deserialize(JsonElement json, Type type, JsonDeserializationContext context) 
    throws JsonParseException {

    Type mapType = new TypeToken<Map<String, String>>() {}.getType();
    Map<String, String> data = context.deserialize(json, mapType);

    return new Holder(data);
  }  
}

然后在创建 Gson 对象：

GsonBuilder gsonBuilder = new GsonBuilder();
gsonBuilder.registerTypeAdapter(Holder.class, new HodlerDeserializer());
Gson gson = gsonBuilder.create();

最后，你解析你的JSON，如下所示：

And finally, you parse your JSON like this:

Type responseType = new TypeToken<Map<String, Holder>>() {}.getType();
Map<String, Holder> response = gson.fromJson(jsonLine, responseType);

您可能需要查看Gson的文档以进行自定义（de）serialization 和我的另一个答案获得更多信息...

You may want to look at Gson's docs for custom (de)serialization and this other answer of mine to get more info...

注意：这个答案已经编辑，以便在评论/聊天中讨论后更清晰。

这篇关于使用Gson自定义反序列化成地图的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！