Test customizing the Jackson object mapper (#30670)

Starting with https://github.com/FasterXML/jackson-databind/issues/2683
Jackson will no longer use the generic bean serialization when serializing a
`java.time.Instant`, but throw an error (since the bean serialization
doesn't make sense for those types anyway).

Our test relied on the bean serialization to test using custom object
mappers. This PR improves the test to use a 'real' custom mapper instead
of just relying on the bean fallback.

.github/workflows/scala3-build.yml

@@ -26,7 +26,7 @@ jobs:
           - akka-discovery/test
           - akka-persistence/compile
           - akka-pki/test
-          - akka-serialization-jackson/Test/compile
+          - akka-serialization-jackson/test
           - akka-slf4j/test
           - akka-stream/test akka-stream-testkit/test akka-stream-tests/test
           - akka-stream-tests-tck/test

akka-serialization-jackson/src/test/scala/akka/serialization/jackson/JacksonSerializerSpec.scala

@@ -15,11 +15,9 @@ import java.util.Locale
 import java.util.Optional
 import java.util.UUID
 import java.util.logging.FileHandler
-
 import scala.collection.immutable
 import scala.concurrent.duration.FiniteDuration
 import scala.concurrent.duration._
-
 import com.fasterxml.jackson.annotation.JsonIgnore
 import com.fasterxml.jackson.annotation.JsonSubTypes
 import com.fasterxml.jackson.annotation.JsonTypeInfo
@@ -34,18 +32,20 @@ import com.fasterxml.jackson.databind.MapperFeature
 import com.fasterxml.jackson.databind.Module
 import com.fasterxml.jackson.databind.ObjectMapper
 import com.fasterxml.jackson.databind.SerializationFeature
+import com.fasterxml.jackson.databind.SerializerProvider
 import com.fasterxml.jackson.databind.annotation.JsonDeserialize
 import com.fasterxml.jackson.databind.annotation.JsonSerialize
 import com.fasterxml.jackson.databind.exc.InvalidTypeIdException
 import com.fasterxml.jackson.databind.json.JsonMapper
 import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule
+import com.fasterxml.jackson.databind.module.SimpleModule
 import com.fasterxml.jackson.module.scala.JsonScalaEnumeration
+
 import scala.annotation.nowarn
 import com.typesafe.config.ConfigFactory
 import org.scalatest.BeforeAndAfterAll
 import org.scalatest.matchers.should.Matchers
 import org.scalatest.wordspec.AnyWordSpecLike
-
 import akka.actor.ActorRef
 import akka.actor.ActorSystem
 import akka.actor.Address
@@ -458,6 +458,20 @@ class JacksonJsonSerializerSpec extends JacksonSerializerSpec("jackson-json") {
     import ScalaTestMessages._
 
     "be possible to create custom ObjectMapper" in {
+      val customJavaTimeModule = new SimpleModule() {
+        import com.fasterxml.jackson.databind.ser.std._
+        addSerializer(classOf[Instant], new StdSerializer[Instant](classOf[Instant]) {
+          override def serialize(value: Instant, gen: JsonGenerator, provider: SerializerProvider): Unit = {
+            gen.writeStartObject()
+            gen.writeFieldName("nanos")
+            gen.writeNumber(value.getNano)
+            gen.writeFieldName("custom")
+            gen.writeString("field")
+            gen.writeEndObject()
+          }
+        })
+      }
+
       val customJacksonObjectMapperFactory = new JacksonObjectMapperFactory {
         override def newObjectMapper(bindingName: String, jsonFactory: JsonFactory): ObjectMapper = {
           if (bindingName == "jackson-json") {
@@ -483,7 +497,7 @@ class JacksonJsonSerializerSpec extends JacksonSerializerSpec("jackson-json") {
             bindingName: String,
             configuredModules: immutable.Seq[Module]): immutable.Seq[Module] =
           if (bindingName == "jackson-json")
-            configuredModules.filterNot(_.isInstanceOf[JavaTimeModule])
+            configuredModules.filterNot(_.isInstanceOf[JavaTimeModule]) :+ customJavaTimeModule
           else
             super.overrideConfiguredModules(bindingName, configuredModules)
 
@@ -529,10 +543,10 @@ class JacksonJsonSerializerSpec extends JacksonSerializerSpec("jackson-json") {
 
         val msg = InstantCommand(Instant.ofEpochMilli(1559907792075L))
         val json = serializeToJsonString(msg, sys)
-        // using the custom ObjectMapper with pretty printing enabled, and no JavaTimeModule
+        // using the custom ObjectMapper with pretty printing enabled, and a custom JavaTimeModule
         json should include("""  "instant" : {""")
-        json should include("""    "nanos" : 75000000,""")
-        json should include("""    "seconds" : 1559907792""")
+        json should include("""    "nanos" : 75000000""")
+        json should include("""    "custom" : "field"""")
       }
     }