fix: 修复 fastjson1 兼容层 JSONPath 连续写入失效问题 (#7697)

* fix: 修复 fastjson1 兼容层 JSONPath 连续写入失效问题

* refactor: 统一 fastjson1 兼容层 live-wrapper 适配

* test: 完善 fastjson1 live-wrapper 回归测试

* test: 补充 core JSONArray live-wrapper 回归测试

* test: 补充 JSONArray.get live-wrapper 回归测试

Author: jianjindream

fastjson1-compatible/src/main/java/com/alibaba/fastjson/JSON.java

@@ -2318,6 +2318,22 @@ public static Object adaptResult(Object result) {
         return adaptResult(result, 0);
     }
 
+    /**
+     * Returns a live wrapper sharing state with the underlying fastjson2 container;
+     * mutations propagate to the parent. Use in {@code get()}-family accessors where
+     * JSONPath navigation must see writes. Use {@link #adaptResult(Object)} for
+     * independent snapshots.
+     */
+    static Object adaptResultLive(Object result) {
+        if (result instanceof com.alibaba.fastjson2.JSONObject) {
+            return new JSONObject((com.alibaba.fastjson2.JSONObject) result);
+        }
+        if (result instanceof com.alibaba.fastjson2.JSONArray) {
+            return new JSONArray((com.alibaba.fastjson2.JSONArray) result);
+        }
+        return result;
+    }
+
     private static Object adaptResult(Object result, int level) {
         if (level > MAX_LEVEL) {
             throw new JSONException("level too large : " + level);

fastjson1-compatible/src/main/java/com/alibaba/fastjson/JSONArray.java

@@ -592,7 +592,8 @@ public boolean containsAll(Collection c) {
 
     @Override
     public Object get(int index) {
-        return adaptResult(list.get(index));
+        Object value = list.get(index);
+        return adaptResultLive(value);
     }
 
     /**

fastjson1-compatible/src/main/java/com/alibaba/fastjson/JSONObject.java

@@ -127,7 +127,7 @@ public Object get(Object key) {
             val = map.get(key.toString());
         }
 
-        return adaptResult(val);
+        return adaptResultLive(val);
     }
 
     public JSONObject getJSONObject(String key) {

fastjson1-compatible/src/test/java/com/alibaba/fastjson/v2issues/Issue7690.java

@@ -0,0 +1,83 @@
+package com.alibaba.fastjson.v2issues;
+
+import com.alibaba.fastjson.JSONArray;
+import com.alibaba.fastjson.JSONObject;
+import com.alibaba.fastjson.JSONPath;
+import org.junit.jupiter.api.Test;
+
+import java.util.concurrent.atomic.AtomicReference;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertSame;
+
+public class Issue7690 {
+    @Test
+    public void testSetFieldAfterAutoCreatingArrayElement() {
+        JSONObject root = new JSONObject();
+
+        JSONObject item = new JSONObject();
+        item.put("title", "1");
+        item.put("value", "110");
+
+        JSONArray testArray = new JSONArray();
+        testArray.add(item);
+        root.put("test", testArray);
+
+        JSONPath.set(root, "$.test[1].title", 2);
+        assertEquals(2, JSONPath.eval(root, "$.test[1].title"));
+
+        JSONPath.set(root, "$.test[1].value", 220);
+        assertEquals(2, JSONPath.eval(root, "$.test[1].title"));
+        assertEquals(220, JSONPath.eval(root, "$.test[1].value"));
+    }
+
+    @Test
+    public void testGetReturnsLiveWrapperForCoreJSONObject() {
+        JSONObject root = new JSONObject();
+        root.put("test", new com.alibaba.fastjson2.JSONObject());
+
+        JSONObject test = (JSONObject) root.get("test");
+        test.put("value", 220);
+
+        assertEquals(220, JSONPath.eval(root, "$.test.value"));
+    }
+
+    @Test
+    public void testGetReturnsLiveWrapperForCoreJSONArray() {
+        JSONObject root = new JSONObject();
+        root.put("arr", new com.alibaba.fastjson2.JSONArray());
+
+        JSONArray arr = (JSONArray) root.get("arr");
+        arr.add(220);
+
+        assertEquals(220, JSONPath.eval(root, "$.arr[0]"));
+    }
+
+    @Test
+    public void testArrayGetReturnsLiveWrapperForCoreJSONObject() {
+        JSONArray arr = new JSONArray();
+        arr.add(new com.alibaba.fastjson2.JSONObject());
+
+        JSONObject obj = (JSONObject) arr.get(0);
+        obj.put("value", 42);
+
+        JSONObject obj2 = (JSONObject) arr.get(0);
+        assertEquals(42, obj2.get("value"));
+    }
+
+    @Test
+    public void testLiveWrapperIterationExposesUnderlyingCoreNestedContainers() {
+        JSONObject root = new JSONObject();
+        JSONPath.set(root, "$.a.b.c", 1);
+
+        JSONObject a = (JSONObject) root.get("a");
+        Object value = a.values().iterator().next();
+        Object entryValue = a.entrySet().iterator().next().getValue();
+        AtomicReference<Object> forEachValue = new AtomicReference<>();
+        a.forEach((key, item) -> forEachValue.set(item));
+
+        assertEquals(com.alibaba.fastjson2.JSONObject.class, value.getClass());
+        assertSame(value, entryValue);
+        assertSame(value, forEachValue.get());
+    }
+}