android - 如何阻止 Moshi 解析特定的对象属性

Question

我的 JSON 响应(来自服务器)具有 JSON 对象的属性，但我不想解析它们，而是想将其中一些保留为 JSON 编码的字符串。

例如:

{
"date": "23-03-2019",
"changed": true,
"data": {
    "login": "9999999",
    "loginFormatted": "999 99 99",
    }
}

这里我想将“数据”属性解析为字符串。我该怎么做？ (我使用的是 Retrofit v2.4.0 和 Moshi v1.5.0)

我的响应模型类:

public class Response {
    @Json(name = "date")
    public long date;
    @Json(name = "changed")
    public boolean changed;
    @Json(name = "data")
    public String data;
}

Answer 1

当 Moshi 查看 Response 的层次结构时类，它决定使用 JsonAdapter<String>解析字段 data .所以解决办法就是告诉Moshi不要用JsonAdapter<String>解析它但将任务委托(delegate)给我们的 JsonAdapter .

说话很便宜，这是代码。

class KeepAsJsonString {
  public void run() throws Exception {
    String json = "" +
      "{\n" +
      "\"date\": \"23-03-2019\",\n" +
      "\"changed\": true,\n" +
      "\"data\": {\n" +
      "    \"login\": \"9999999\",\n" +
      "    \"loginFormatted\": \"999 99 99\"\n" +
      "    }\n" +
      "}";

    Moshi moshi = new Moshi.Builder().add(new DataToStringAdapter()).build();
    JsonAdapter<Response> jsonAdapter = moshi.adapter(Response.class);

    Response response = jsonAdapter.fromJson(json);
    System.out.println(response.data); // {"login":"9999999","loginFormatted":"999 99 99"}
  }

  static class Response {
    @Json(name = "date")
    public String date;
    @Json(name = "changed")
    public boolean changed;
    // Ask moshi to forward the intermediate result to some function with a String annotated with @DataString,
    // in our case, DataToStringAdapter.fromJson() and DataToStringAdapter.toJson()
    @Json(name = "data")
    public @DataString String data;
  }

  @Retention(RUNTIME)
  @JsonQualifier
  public @interface DataString {
  }

  static class DataToStringAdapter {
    @ToJson
    void toJson(JsonWriter writer, @DataString String string) throws IOException {
      // Write raw JSON string
      writer.value(new Buffer().writeUtf8(string));
    }

    @FromJson @DataString
    String fromJson(JsonReader reader, JsonAdapter<Object> delegate) throws IOException {
      // Now the intermediate data object (a Map) comes here
      Object data = reader.readJsonValue();
      // Just delegate to JsonAdapter<Object>, so we got a JSON string of the object
      return delegate.toJson(data);
    }
  }

  public static void main(String[] args) throws Exception {
    new KeepAsJsonString().run();
  }
}

在 Kotlin 中它看起来像这样:

@JsonQualifier
@Retention(AnnotationRetention.RUNTIME)
@Target(AnnotationTarget.FIELD, AnnotationTarget.VALUE_PARAMETER, AnnotationTarget.FUNCTION)
annotation class DataString

internal class JsonObjectToStringJsonAdapter {

    @ToJson
    fun toJson(@DataString s: String): String {
        return s
    }

    @FromJson
    @DataString
    fun fromJson(reader: JsonReader, adapter: JsonAdapter<Any>): String {
        val jsonObject: Any = reader.readJsonValue()!!
        return adapter.toJson(jsonObject)
    }
}

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更新:

正如 Eric Cochran 提到的，当 issue 时，将有一种更有效的方式 ( JsonReader.readJsonString() ) 将 JSON 读取为字符串是固定的。