fix: correct self reference serialization

services/src/main/kotlin/spp/probe/services/common/ModelSerializer.kt

@@ -20,8 +20,8 @@ import com.google.gson.*
 import com.google.gson.reflect.TypeToken
 import com.google.gson.stream.JsonReader
 import com.google.gson.stream.JsonWriter
-import spp.probe.services.common.serialize.RuntimeClassNameTypeAdapterFactory
 import spp.probe.services.common.serialize.CappedTypeAdapterFactory
+import spp.probe.services.common.serialize.RuntimeClassNameTypeAdapterFactory
 import java.io.IOException
 import java.io.OutputStream
 import java.util.*

services/src/main/kotlin/spp/probe/services/common/serialize/RuntimeClassNameTypeAdapterFactory.kt

@@ -18,9 +18,11 @@ package spp.probe.services.common.serialize
 
 import com.google.gson.*
 import com.google.gson.internal.Streams
+import com.google.gson.internal.bind.JsogRegistry
 import com.google.gson.reflect.TypeToken
 import com.google.gson.stream.JsonReader
 import com.google.gson.stream.JsonWriter
+import org.apache.skywalking.apm.agent.core.logging.api.LogManager
 import java.io.IOException
 
 /**
@@ -113,6 +115,9 @@ import java.io.IOException
  */
 class RuntimeClassNameTypeAdapterFactory<T> private constructor(baseType: Class<*>?, typeFieldName: String?) :
     TypeAdapterFactory {
+
+    private val log = LogManager.getLogger(RuntimeClassNameTypeAdapterFactory::class.java)
+
     private val baseType: Class<*>
     private val typeFieldName: String
     private val labelToSubtype: MutableMap<String, Class<*>> = LinkedHashMap()
@@ -224,6 +229,23 @@ class RuntimeClassNameTypeAdapterFactory<T> private constructor(baseType: Class<
                         Streams.write(jsonObject, out)
                     } else {
                         val clone = JsonObject()
+
+                        //search for self-references
+                        try {
+                            srcType.declaredFields.forEach {
+                                it.isAccessible = true
+                                val fieldValue = it.get(value)
+                                if (fieldValue === value) {
+                                    val selfRef = JsonObject()
+                                    selfRef.addProperty("@ref", JsogRegistry.get().geId(value))
+                                    selfRef.addProperty("@class", value.javaClass.name)
+                                    clone.add(it.name, selfRef)
+                                }
+                            }
+                        } catch (e: Throwable) {
+                            log.error("Error while serializing self-references", e)
+                        }
+
                         clone.add(typeFieldName, JsonPrimitive(label))
                         for ((key, value1) in jsonObject.entrySet()) {
                             clone.add(key, value1)

services/src/test/kotlin/spp/probe/services/common/serialize/JsogTest.kt

@@ -0,0 +1,82 @@
+/*
+ * Source++, the open-source live coding platform.
+ * Copyright (C) 2022 CodeBrig, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package spp.probe.services.common.serialize
+
+import io.vertx.core.json.JsonObject
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertTrue
+import org.junit.Test
+import spp.probe.services.common.ModelSerializer
+
+class JsogTest {
+
+    class RootSelfRef {
+        var self: RootSelfRef? = null
+    }
+
+    @Test
+    fun testRootSelfRef() {
+        val rootSelfRef = RootSelfRef()
+        rootSelfRef.self = rootSelfRef
+        val json = ModelSerializer.INSTANCE.toExtendedJson(rootSelfRef)
+        val jsonObject = JsonObject(json)
+
+        assertEquals(3, jsonObject.size())
+        assertTrue(jsonObject.containsKey("@class"))
+        assertTrue(jsonObject.containsKey("@id"))
+        assertTrue(jsonObject.containsKey("self"))
+
+        val self = jsonObject.getJsonObject("self")
+        assertEquals(2, self.size())
+        assertTrue(self.containsKey("@class"))
+        assertTrue(self.containsKey("@ref"))
+        assertEquals(self.getString("@ref"), jsonObject.getString("@id"))
+    }
+
+    class InnerSelfRef {
+        class InnerSelfRef2 {
+            var selfRef: InnerSelfRef? = null
+        }
+
+        var self2: InnerSelfRef2? = null
+    }
+
+    @Test
+    fun testInnerSelfRef() {
+        val innerSelfRef = InnerSelfRef()
+        innerSelfRef.self2 = InnerSelfRef.InnerSelfRef2().apply { this.selfRef = innerSelfRef }
+        val json = ModelSerializer.INSTANCE.toExtendedJson(innerSelfRef)
+        val jsonObject = JsonObject(json)
+
+        assertEquals(3, jsonObject.size())
+        assertTrue(jsonObject.containsKey("@class"))
+        assertTrue(jsonObject.containsKey("@id"))
+        assertTrue(jsonObject.containsKey("self2"))
+
+        val self2 = jsonObject.getJsonObject("self2")
+        assertEquals(3, self2.size())
+        assertTrue(self2.containsKey("@class"))
+        assertTrue(self2.containsKey("@id"))
+        assertTrue(self2.containsKey("selfRef"))
+
+        val selfRef = self2.getJsonObject("selfRef")
+        assertEquals(2, selfRef.size())
+        assertTrue(selfRef.containsKey("@class"))
+        assertTrue(selfRef.containsKey("@ref"))
+        assertEquals(selfRef.getString("@ref"), jsonObject.getString("@id"))
+    }
+}