From a179caa1b271a1d3db667b5fad5e49dd1789a697 Mon Sep 17 00:00:00 2001
From: "shaojin.wensj" <shaojin.wensj@alibaba-inc.com>
Date: Wed, 8 Jun 2022 04:02:54 +0800
Subject: [PATCH] bug fix for JSONPath.set if parent is null

---
 .../java/com/alibaba/fastjson2/JSONPath.java  | 28 +++++++++++++++++++
 .../alibaba/fastjson2/issues/Issue424.java    | 16 +++++++++++
 2 files changed, 44 insertions(+)
 create mode 100644 core/src/test/java/com/alibaba/fastjson2/issues/Issue424.java

diff --git a/core/src/main/java/com/alibaba/fastjson2/JSONPath.java b/core/src/main/java/com/alibaba/fastjson2/JSONPath.java
index b97546186f..b2c33f34b5 100644
--- a/core/src/main/java/com/alibaba/fastjson2/JSONPath.java
+++ b/core/src/main/java/com/alibaba/fastjson2/JSONPath.java
@@ -3156,6 +3156,34 @@ public void set(Object root, Object value) {
                 }
 
                 segment.eval(context);
+                if (context.value == null && nextSegment != null) {
+                    if (value == null) {
+                        return;
+                    }
+
+                    Object parentObject;
+                    if (i == 0) {
+                        parentObject = root;
+                    } else {
+                        parentObject = context.parent.value;
+                    }
+
+                    Object emptyValue;
+                    if (nextSegment instanceof IndexSegment) {
+                        emptyValue = new JSONArray();
+                    } else if (nextSegment instanceof NameSegment) {
+                        emptyValue = new JSONObject();
+                    } else {
+                        return;
+                    }
+                    context.value = emptyValue;
+
+                    if (parentObject instanceof Map && segment instanceof NameSegment) {
+                        ((Map) parentObject).put(((NameSegment) segment).name, emptyValue);
+                    } else if (parentObject instanceof List && segment instanceof IndexSegment) {
+                        ((List) parentObject).set(((IndexSegment) segment).index, emptyValue);
+                    }
+                }
             }
             context = new Context(this, context, segments.get(0), null, 0L);
             context.root = root;
diff --git a/core/src/test/java/com/alibaba/fastjson2/issues/Issue424.java b/core/src/test/java/com/alibaba/fastjson2/issues/Issue424.java
new file mode 100644
index 0000000000..a3c8ffe33c
--- /dev/null
+++ b/core/src/test/java/com/alibaba/fastjson2/issues/Issue424.java
@@ -0,0 +1,16 @@
+package com.alibaba.fastjson2.issues;
+
+import com.alibaba.fastjson2.JSONObject;
+import com.alibaba.fastjson2.JSONPath;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class Issue424 {
+    @Test
+    public void test() {
+        JSONObject jsonObject = new JSONObject();
+        JSONPath.set(jsonObject, "a[0].b", 1);
+        assertEquals("{\"a\":[{\"b\":1}]}", jsonObject.toString());
+    }
+}