perf(core): Lazily create reflection JSON serializer

Defer creation of JsonReflectionObjectSerializer until unknown-object reflection serialization is needed. Normal SDK payloads use explicit serializers, so this avoids allocating unused reflection serializer state for each writer.

Author: adinauer

sentry/api/sentry.api

@@ -1313,7 +1313,6 @@ public final class io/sentry/JsonObjectReader : io/sentry/ObjectReader {
 
 public final class io/sentry/JsonObjectSerializer {
 	public static final field OBJECT_PLACEHOLDER Ljava/lang/String;
-	public final field jsonReflectionObjectSerializer Lio/sentry/JsonReflectionObjectSerializer;
 	public fun <init> (I)V
 	public fun serialize (Lio/sentry/ObjectWriter;Lio/sentry/ILogger;Ljava/lang/Object;)V
 }

sentry/src/main/java/io/sentry/JsonObjectSerializer.java

@@ -28,10 +28,11 @@ public final class JsonObjectSerializer {
 
   public static final String OBJECT_PLACEHOLDER = "[OBJECT]";
 
-  public final JsonReflectionObjectSerializer jsonReflectionObjectSerializer;
+  private final int maxDepth;
+  private @Nullable JsonReflectionObjectSerializer jsonReflectionObjectSerializer;
 
   public JsonObjectSerializer(int maxDepth) {
-    jsonReflectionObjectSerializer = new JsonReflectionObjectSerializer(maxDepth);
+    this.maxDepth = maxDepth;
   }
 
   public void serialize(
@@ -127,7 +128,7 @@ public void serialize(
       writer.value(object.toString());
     } else {
       try {
-        Object serializableObject = jsonReflectionObjectSerializer.serialize(object, logger);
+        Object serializableObject = getJsonReflectionObjectSerializer().serialize(object, logger);
         serialize(writer, logger, serializableObject);
       } catch (Exception exception) {
         logger.log(SentryLevel.ERROR, "Failed serializing unknown object.", exception);
@@ -138,6 +139,13 @@ public void serialize(
 
   // Helper
 
+  private @NotNull JsonReflectionObjectSerializer getJsonReflectionObjectSerializer() {
+    if (jsonReflectionObjectSerializer == null) {
+      jsonReflectionObjectSerializer = new JsonReflectionObjectSerializer(maxDepth);
+    }
+    return jsonReflectionObjectSerializer;
+  }
+
   private void serializeDate(
       @NotNull ObjectWriter writer, @NotNull ILogger logger, @NotNull Date date)
       throws IOException {

sentry/src/test/java/io/sentry/JsonObjectSerializerTest.kt

@@ -7,6 +7,8 @@ import java.util.Locale
 import java.util.TimeZone
 import java.util.concurrent.atomic.AtomicBoolean
 import java.util.concurrent.atomic.AtomicIntegerArray
+import kotlin.test.assertNotNull
+import kotlin.test.assertNull
 import org.junit.Test
 import org.mockito.kotlin.inOrder
 import org.mockito.kotlin.mock
@@ -192,6 +194,21 @@ internal class JsonObjectSerializerTest {
     verify(jsonSerializable).serialize(fixture.writer, fixture.logger)
   }
 
+  @Test
+  fun `serialize json serializable does not create reflection serializer`() {
+    val serializer = fixture.getSUT()
+    val jsonSerializable: JsonSerializable = mock()
+    serializer.serialize(fixture.writer, fixture.logger, jsonSerializable)
+    assertNull(serializer.reflectionObjectSerializer)
+  }
+
+  @Test
+  fun `serialize unknown object creates reflection serializer`() {
+    val serializer = fixture.getSUT()
+    serializer.serialize(fixture.writer, fixture.logger, object {})
+    assertNotNull(serializer.reflectionObjectSerializer)
+  }
+
   @Test
   fun `serialize unknown object without data`() {
     val value = object {}
@@ -355,3 +372,10 @@ internal class JsonObjectSerializerTest {
 data class ClassWithEnumProperty(val enumProperty: DataCategory)
 
 data class ClassWithLocaleProperty(val localeProperty: Locale)
+
+private val JsonObjectSerializer.reflectionObjectSerializer: JsonReflectionObjectSerializer?
+  get() {
+    val field = JsonObjectSerializer::class.java.getDeclaredField("jsonReflectionObjectSerializer")
+    field.isAccessible = true
+    return field.get(this) as JsonReflectionObjectSerializer?
+  }