moshi-adapters

A collection of custom adapters for Moshi.

Usage

Gradle dependency

dependencies {
  implementation("dev.zacsweers.moshix:moshi-adapters:<version>")
}

Adapters

@JsonString

A JsonQualifier for use with String properties to indicate that their value should be propagated with the raw JSON string representation of that property rather than a decoded type.

val moshi = Moshi.Builder()
  .add(JsonString.Factory())
  .build()

@JsonClass(generateAdapter = true)
data class Message(
  val type: String,
  @JsonString val data: String
)

@AdaptedBy

An annotation that indicates the Moshi JsonAdapter or JsonAdapter.Factory to use with a class or property (as a @JsonQualifier).

val moshi = Moshi.Builder()
  .add(AdaptedBy.Factory())
  .build()

@AdaptedBy(StringAliasAdapter::class)
data class StringAlias(val value: String)

class StringAliasAdapter : JsonAdapter<StringAlias>() {
  override fun fromJson(reader: JsonReader): StringAlias? {
    return StringAlias(reader.nextString())
  }

  override fun toJson(writer: JsonWriter, value: StringAlias?) {
    if (value == null) {
      writer.nullValue()
      return
    }
    writer.value(value.value)
  }
}

@TrackUnknownKeys

An annotation to help track unknown keys in JSON.

Note that this adapter is slow because it must parse the entire JSON object ahead of time, then writes and re-reads it.

In general, it is not recommended to use this adapter in production unless absolutely necessary or to sample its usage. This should be used for debugging/logging information only.

Usage:

val moshi = Moshi.Builder()
  .add(TrackUnknownKeys.Factory())
  .build()

@TrackUnknownKeys
@JsonClass(generateAdapter = true)
data class Message(
  val data: String
)

// JSON of {"data": "value", "foo": "bar"} would report an unknown "foo"