[ECO-5386] Implement JSON and MessagePack serialization for ObjectMessage

1. Added jackson-dataformat-msgpack 0.8.11 dependency for automatic msgpack handling
2. Implemented JSON serialization via ObjectMessage.toJsonObject() and JsonObject.toObjectMessage() extensions
3. Implemented MessagePack serialization via ObjectMessage.writeTo() and MessageUnpacker.readObjectMessage() extensions
4. Added @SerializedName("object") annotation for proper field naming consistency

Author: sacOO7

gradle/libs.versions.toml

@@ -25,6 +25,7 @@ mockk = "1.14.2"
 turbine = "1.2.0"
 ktor = "3.1.3"
 jetbrains-annoations = "26.0.2"
+jackson-msgpack = "0.8.11" # Compatible with msgpack-core 0.8.11
 
 [libraries]
 gson = { group = "com.google.code.gson", name = "gson", version.ref = "gson" }
@@ -54,6 +55,7 @@ turbine = { group = "app.cash.turbine", name = "turbine", version.ref = "turbine
 ktor-client-core = { module = "io.ktor:ktor-client-core", version.ref = "ktor" }
 ktor-client-cio = { module = "io.ktor:ktor-client-cio", version.ref = "ktor" }
 jetbrains = { group = "org.jetbrains", name = "annotations", version.ref = "jetbrains-annoations" }
+jackson-msgpack = { group = "org.msgpack", name = "jackson-dataformat-msgpack", version.ref = "jackson-msgpack" }
 
 [bundles]
 common = ["msgpack", "vcdiff-core"]

live-objects/build.gradle.kts

@@ -13,6 +13,7 @@ dependencies {
     implementation(project(":java"))
     implementation(libs.bundles.common)
     implementation(libs.coroutine.core)
+    implementation(libs.jackson.msgpack)
 
     testImplementation(kotlin("test"))
     testImplementation(libs.bundles.kotlin.tests)

live-objects/src/main/kotlin/io/ably/lib/objects/ObjectMessage.kt

@@ -1,5 +1,8 @@
 package io.ably.lib.objects
 
+import com.fasterxml.jackson.annotation.JsonProperty
+import com.google.gson.annotations.SerializedName
+
 /**
  * An enum class representing the different actions that can be performed on an object.
  * Spec: OOP2
@@ -318,6 +321,8 @@ internal data class ObjectMessage(
    * the `ProtocolMessage` encapsulating it is `OBJECT_SYNC`.
    * Spec: OM2g
    */
+  @SerializedName("object")
+  @JsonProperty("object")
   val objectState: ObjectState? = null,
 
   /**

live-objects/src/main/kotlin/io/ably/lib/objects/Serialization.kt

@@ -1,31 +1,88 @@
+@file:Suppress("UNCHECKED_CAST")
+
 package io.ably.lib.objects
 
-import com.google.gson.Gson
-import com.google.gson.GsonBuilder
-import com.google.gson.JsonArray
+import com.fasterxml.jackson.databind.ObjectMapper
+import com.google.gson.*
+import org.msgpack.core.MessagePack
 import org.msgpack.core.MessagePacker
 import org.msgpack.core.MessageUnpacker
+import org.msgpack.jackson.dataformat.MessagePackFactory
+
+// Gson instance for JSON serialization/deserialization
+internal val gson: Gson = GsonBuilder().create()
 
-internal val gson: Gson = createGsonSerializer()
+// Jackson ObjectMapper for MessagePack serialization (respects @JsonProperty annotations)
+// Caches type metadata and serializers for ObjectMessage class after first use, so super fast!!
+private val msgpackMapper = ObjectMapper(MessagePackFactory())
+
+internal fun ObjectMessage.toJsonObject(): JsonObject {
+  return gson.toJsonTree(this).asJsonObject
+}
 
-private fun createGsonSerializer(): Gson {
-  return GsonBuilder().create() // Do not call serializeNulls() to omit null values
+internal fun JsonObject.toObjectMessage(): ObjectMessage {
+  return gson.fromJson(this, ObjectMessage::class.java)
 }
 
+internal fun ObjectMessage.writeTo(packer: MessagePacker) {
+  // Jackson automatically creates the correct msgpack map structure
+  val msgpackBytes = msgpackMapper.writeValueAsBytes(this)
+
+  // Parse the msgpack bytes to get the structured value
+  val tempUnpacker = MessagePack.newDefaultUnpacker(msgpackBytes)
+  val msgpackValue = tempUnpacker.unpackValue()
+  tempUnpacker.close()
+
+  // Pack the structured value using the provided packer
+  packer.packValue(msgpackValue)
+}
+
+internal fun MessageUnpacker.readObjectMessage(): ObjectMessage {
+  // Read the msgpack value from the unpacker
+  val msgpackValue = this.unpackValue()
+
+  // Convert the msgpack value back to bytes
+  val tempPacker = MessagePack.newDefaultBufferPacker()
+  tempPacker.packValue(msgpackValue)
+  val msgpackBytes = tempPacker.toByteArray()
+  tempPacker.close()
+
+  // Let Jackson deserialize the msgpack bytes back to ObjectMessage
+  return msgpackMapper.readValue(msgpackBytes, ObjectMessage::class.java)
+}
+
+/**
+ * Default implementation of {@link LiveObjectSerializer} that handles serialization/deserialization
+ * of ObjectMessage arrays for both JSON and MessagePack formats using Jackson and Gson.
+ * Dynamically loaded by LiveObjectsHelper#getLiveObjectSerializer() to avoid hard dependencies.
+ */
+@Suppress("unused") // Used via reflection in LiveObjectsHelper
 internal class DefaultLiveObjectSerializer : LiveObjectSerializer {
+
   override fun readMsgpackArray(unpacker: MessageUnpacker): Array<Any> {
-    TODO("Not yet implemented")
+    val objectMessagesCount = unpacker.unpackArrayHeader()
+    return Array(objectMessagesCount) { unpacker.readObjectMessage() }
   }
 
   override fun writeMsgpackArray(objects: Array<out Any>?, packer: MessagePacker) {
-    TODO("Not yet implemented")
+    val objectMessages: Array<ObjectMessage> = objects as Array<ObjectMessage>
+    packer.packArrayHeader(objectMessages.size)
+    objectMessages.forEach { it.writeTo(packer) }
   }
 
   override fun readFromJsonArray(json: JsonArray): Array<Any> {
-    TODO("Not yet implemented")
+    return json.map { element ->
+      if (element.isJsonObject) element.asJsonObject.toObjectMessage()
+      else throw JsonParseException("Expected JsonObject, but found: $element")
+    }.toTypedArray()
   }
 
   override fun asJsonArray(objects: Array<out Any>?): JsonArray {
-    TODO("Not yet implemented")
+    val objectMessages: Array<ObjectMessage> = objects as Array<ObjectMessage>
+    val jsonArray = JsonArray()
+    for (objectMessage in objectMessages) {
+      jsonArray.add(objectMessage.toJsonObject())
+    }
+    return jsonArray
   }
 }