notion.api.v1.json.GsonUnknownFieldDetection.kt Maven / Gradle / Ivy

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package notion.api.v1.json

import com.google.gson.Gson
import com.google.gson.JsonParseException
import com.google.gson.TypeAdapter
import com.google.gson.TypeAdapterFactory
import com.google.gson.internal.bind.ReflectiveTypeAdapterFactory
import com.google.gson.reflect.TypeToken
import java.lang.reflect.Field

class GsonUnknownFieldDetection : TypeAdapterFactory {

  override fun  create(gson: Gson, type: TypeToken?): TypeAdapter? {
    // If the type adapter is a reflective type adapter, we want to modify the implementation
    // using
    // reflection. The
    // trick is to replace the Map object used to lookup the property name. Instead of returning
    // null if the
    // property is not found, we throw a Json exception to terminate the deserialization.
    val delegate = gson.getDelegateAdapter(this, type)

    // Check if the type adapter is a reflective, cause this solution only work for reflection.
    if (delegate is ReflectiveTypeAdapterFactory.Adapter<*>) {
      try {
        // Get reference to the existing boundFields.
        val f: Field = delegate.javaClass.getDeclaredField("boundFields")
        f.isAccessible = true
        var boundFields = f.get(delegate) as Map<*, *>
        val sb = StringBuilder()
        for (key in boundFields.keys) {
          sb.append("$key, ")
        }
        val boundFieldsStr = sb.append("...").toString()

        // Then replace it with our implementation throwing exception if the value is null.
        boundFields =
            object : LinkedHashMap(boundFields) {
              override fun get(key: Any?): Any? {
                return super.get(key)
                    ?: throw JsonParseException(
                        "Unknown property detected: $key in $boundFieldsStr")
              }
            }
        // Finally, push our custom map back using reflection.
        f.set(delegate, boundFields)
      } catch (e: Exception) {
        // Should never happen if the implementation doesn't change.
        throw IllegalStateException(e)
      }
    }
    return delegate
  }
}