From 30c88b6e8fa9c720db998bb696dbad52a34dd6fd Mon Sep 17 00:00:00 2001
From: "shaojin.wensj" <shaojin.wensj@alibaba-inc.com>
Date: Wed, 17 Jan 2024 23:05:57 +0800
Subject: [PATCH] JSON.toJSON support reference, for issue #2187

---
 .../fastjson2/writer/ObjectWriterAdapter.java |  6 ++-
 .../fastjson2/issues_2100/Issue2187.java      | 40 +++++++++++++++++++
 2 files changed, 45 insertions(+), 1 deletion(-)

diff --git a/core/src/main/java/com/alibaba/fastjson2/writer/ObjectWriterAdapter.java b/core/src/main/java/com/alibaba/fastjson2/writer/ObjectWriterAdapter.java
index 69d1bd0ba9..1ad86a64ec 100644
--- a/core/src/main/java/com/alibaba/fastjson2/writer/ObjectWriterAdapter.java
+++ b/core/src/main/java/com/alibaba/fastjson2/writer/ObjectWriterAdapter.java
@@ -649,7 +649,8 @@ public JSONObject toJSONObject(T object, long features) {
                     Collection collection = (Collection) fieldValue;
                     JSONArray array = new JSONArray(collection.size());
                     for (Object item : collection) {
-                        array.add(JSON.toJSON(item));
+                        Object itemJSON = item == object ? jsonObject : JSON.toJSON(item);
+                        array.add(itemJSON);
                     }
                     fieldValue = array;
                 }
@@ -659,6 +660,9 @@ public JSONObject toJSONObject(T object, long features) {
                 continue;
             }
 
+            if (fieldValue == object) {
+                fieldValue = jsonObject;
+            }
             jsonObject.put(fieldWriter.fieldName, fieldValue);
         }
 
diff --git a/core/src/test/java/com/alibaba/fastjson2/issues_2100/Issue2187.java b/core/src/test/java/com/alibaba/fastjson2/issues_2100/Issue2187.java
index e741d5e974..2b21f6b05c 100644
--- a/core/src/test/java/com/alibaba/fastjson2/issues_2100/Issue2187.java
+++ b/core/src/test/java/com/alibaba/fastjson2/issues_2100/Issue2187.java
@@ -7,9 +7,11 @@
 import org.junit.jupiter.api.Test;
 
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.List;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertSame;
 
 public class Issue2187 {
     @Test
@@ -29,4 +31,42 @@ public static class Bean {
 
     public static class Item {
     }
+
+    @Test
+    public void test1() throws Exception {
+        JSONObject object = new JSONObject();
+        object.put("ref", object);
+        assertSame(object, JSON.toJSON(object));
+    }
+
+    @Test
+    public void test2() throws Exception {
+        JSONArray array = new JSONArray();
+        array.add(array);
+        assertSame(array, JSON.toJSON(array));
+    }
+
+    @Test
+    public void test3() throws Exception {
+        Bean3 bean = new Bean3();
+        bean.value = bean;
+        JSONObject json = (JSONObject) JSON.toJSON(bean);
+        assertSame(json, json.get("value"));
+    }
+
+    public static class Bean3 {
+        public Bean3 value;
+    }
+
+    @Test
+    public void test4() throws Exception {
+        Bean4 bean = new Bean4();
+        bean.values = Arrays.asList(bean);
+        JSONObject json = (JSONObject) JSON.toJSON(bean);
+        assertSame(json, json.getJSONArray("values").get(0));
+    }
+
+    public static class Bean4 {
+        public List<Bean4> values;
+    }
 }