android - moshi 自定义 JsonAdapter 跳过坏元素的问题

Question

我有一个用于跳过坏元素的 moshi 自定义 json 适配器，如下所示:

class SkipBadElementsListAdapter(private val elementAdapter: JsonAdapter<Any?>) :
JsonAdapter<List<Any?>>() {
object Factory : JsonAdapter.Factory {
    override fun create(
        type: Type,
        annotations: Set<Annotation>,
        moshi: Moshi
    ): JsonAdapter<*>? {
        if (annotations.isNotEmpty() || Types.getRawType(type) != List::class.java) {
            return null
        }
        val elementType = Types.collectionElementType(type, List::class.java)
        val elementAdapter = moshi.adapter<Any?>(elementType)
        return SkipBadElementsListAdapter(elementAdapter).nullSafe()
    }
}

override fun fromJson(reader: JsonReader): List<Any?>? {

    val result = mutableListOf<Any?>()
    reader.beginArray()
    while (reader.hasNext()) {
        try {
            val peeked = reader.peekJson()
            result += elementAdapter.fromJson(peeked)
        } catch (ignored: JsonDataException) {
            Timber.tag("JsonParseError").d(ignored.toString())
        }
        reader.skipValue()
    }
    reader.endArray()
    return result

}

override fun toJson(writer: JsonWriter, value: List<Any?>?) {

    if (value == null) {
        throw NullPointerException("value was null! Wrap in .nullSafe() to write nullable values.")
    }
    writer.beginArray()
    for (i in value.indices) {
        elementAdapter.toJson(writer, value[i])
    }
    writer.endArray()
}

}

但是在添加了这个自定义 json 适配器后，我在 firebase 中收到了很多 fatal error :

Fatal Exception: java.lang.AssertionError
   at com.squareup.moshi.JsonUtf8Reader.<init>(JsonUtf8Reader.java:118)
   at com.squareup.moshi.JsonUtf8Reader.peekJson(JsonUtf8Reader.java:1076)
   at ir.part.app.signal.core.util.api.SkipBadElementsListAdapter.fromJson(SkipBadElementsListAdapter.java:30)
   at ir.part.app.signal.core.util.api.SkipBadElementsListAdapter.fromJson(SkipBadElementsListAdapter.java:7)
   at com.squareup.moshi.JsonAdapter$2.fromJson(JsonAdapter.java:137)
   at ir.part.app.signal.core.model.SignalListResponseJsonAdapter.fromJson(SignalListResponseJsonAdapter.java:41)
   at ir.part.app.signal.core.model.SignalListResponseJsonAdapter.fromJson(SignalListResponseJsonAdapter.java:17)
   at com.squareup.moshi.JsonAdapter$2.fromJson(JsonAdapter.java:137)
   at retrofit2.converter.moshi.MoshiResponseBodyConverter.convert(MoshiResponseBodyConverter.java:45)
   at retrofit2.converter.moshi.MoshiResponseBodyConverter.convert(MoshiResponseBodyConverter.java:27)
   at retrofit2.OkHttpCall.parseResponse(OkHttpCall.java:225)
   at retrofit2.OkHttpCall$1.onResponse(OkHttpCall.java:121)
   at com.google.firebase.perf.network.zzh.onResponse(zzh.java:22)
   at okhttp3.RealCall$AsyncCall.execute(RealCall.java:203)
   at okhttp3.internal.NamedRunnable.run(NamedRunnable.java:32)
   at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1133)
   at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:607)
   at java.lang.Thread.run(Thread.java:776)

我查看moshi lib代码并猜测“sourcePeek.require”中出现问题:

    JsonUtf8Reader(JsonUtf8Reader copyFrom) {
    ...
    // Make sure our buffer has as many bytes as the source's buffer. This is necessary because
    // JsonUtf8Reader assumes any data it has peeked (like the peekedNumberLength) are buffered.
    try {
      sourcePeek.require(copyFrom.buffer.size());
    } catch (IOException e) {
      throw new AssertionError();
    }
}

我的自定义 moshi 适配器有什么问题？!我想从数据列表中的服务器接收的 json 中跳过坏元素并显示正确的项目。

Answer 1

跳过适配器不知道要跳过多少。您希望它跳到当前列表元素的末尾，崩溃可能部分通过复杂对象离开了 JsonReader。

通过 peekJson() 解决到委托(delegate)适配器和总是 无论是否有异常都跳过。