fix: 改进 FastJsonValueHandler 错误处理并支持 JSON 字符串

- 为 fetch/set 操作添加显式的 JSONException 错误处理
- 当 object 为 String 类型时，防止自动解析 JSON 字符串
- 支持 "$" 作为空路径的别名来表示对象自身
- 添加 JSON 字符串行为的完整测试用例
- 更新版权年份为 2024-2025

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <[email protected]>

Author: CodeCasterX

framework/fit/java/fit-builtin/plugins/fit-value-fastjson/src/main/java/modelengine/fit/value/fastjson/FastJsonValueHandler.java

@@ -1,11 +1,12 @@
-/*---------------------------------------------------------------------------------------------
- *  Copyright (c) 2024 Huawei Technologies Co., Ltd. All rights reserved.
- *  This file is a part of the ModelEngine Project.
- *  Licensed under the MIT License. See License.txt in the project root for license information.
- *--------------------------------------------------------------------------------------------*/
+/*
+ * Copyright (c) 2024-2025 Huawei Technologies Co., Ltd. All rights reserved.
+ * This file is a part of the ModelEngine Project.
+ * Licensed under the MIT License. See License.txt in the project root for license information.
+ */
 
 package modelengine.fit.value.fastjson;
 
+import com.alibaba.fastjson2.JSONException;
 import com.alibaba.fastjson2.JSONPath;
 
 import modelengine.fitframework.annotation.Component;
@@ -21,15 +22,25 @@
  */
 @Component
 public class FastJsonValueHandler implements ValueFetcher, ValueSetter {
+    private static final String $ = "$";
+
     @Override
     public Object fetch(Object object, String propertyPath) {
         if (object == null) {
             return null;
         }
-        if (StringUtils.isBlank(propertyPath)) {
+        if (isObjectSelf(propertyPath)) {
             return object;
-        } else {
+        }
+        if (object instanceof String) {
+            return null;
+        }
+        try {
             return JSONPath.eval(object, this.getParsedPath(propertyPath));
+        } catch (JSONException e) {
+            throw new IllegalArgumentException(StringUtils.format(
+                    "Failed to fetch value by JSONPath. [propertyPath={0}]",
+                    propertyPath), e);
         }
     }
 
@@ -38,20 +49,32 @@ public Object set(Object object, String propertyPath, Object value) {
         if (object == null) {
             return null;
         }
-        if (StringUtils.isBlank(propertyPath)) {
+        if (isObjectSelf(propertyPath)) {
             return value;
         }
-        JSONPath.set(object, this.getParsedPath(propertyPath), value);
-        return object;
+        if (object instanceof String) {
+            return object;
+        }
+        try {
+            JSONPath.set(object, this.getParsedPath(propertyPath), value);
+            return object;
+        } catch (JSONException e) {
+            throw new IllegalArgumentException(StringUtils.format("Failed to set value by JSONPath. [propertyPath={0}]",
+                    propertyPath), e);
+        }
+    }
+
+    private static boolean isObjectSelf(String propertyPath) {
+        return StringUtils.isBlank(propertyPath) || $.equals(propertyPath);
     }
 
     private String getParsedPath(String propertyPath) {
-        if (propertyPath.startsWith("$")) {
+        if (propertyPath.startsWith($)) {
             return propertyPath;
         } else if (propertyPath.startsWith("[")) {
-            return "$" + propertyPath;
+            return $ + propertyPath;
         } else {
-            return "$." + propertyPath;
+            return $ + "." + propertyPath;
         }
     }
 }

framework/fit/java/fit-builtin/plugins/fit-value-fastjson/src/test/java/modelengine/fit/value/fastjson/FastJsonValueFetcherTest.java

@@ -1,8 +1,8 @@
-/*---------------------------------------------------------------------------------------------
- *  Copyright (c) 2024 Huawei Technologies Co., Ltd. All rights reserved.
- *  This file is a part of the ModelEngine Project.
- *  Licensed under the MIT License. See License.txt in the project root for license information.
- *--------------------------------------------------------------------------------------------*/
+/*
+ * Copyright (c) 2024-2025 Huawei Technologies Co., Ltd. All rights reserved.
+ * This file is a part of the ModelEngine Project.
+ * Licensed under the MIT License. See License.txt in the project root for license information.
+ */
 
 package modelengine.fit.value.fastjson;
 
@@ -79,6 +79,29 @@ void shouldReturnNullGivenPropertyPathIsNotEmpty() {
         }
     }
 
+    @Nested
+    @DisplayName("当 object 为 JSON 字符串时")
+    class GivenObjectIsJsonString {
+        private Object object;
+
+        @BeforeEach
+        void setup() {
+            this.object = "{\"k1\":{\"k2\":\"v\"}}";
+        }
+
+        @AfterEach
+        void teardown() {
+            this.object = null;
+        }
+
+        @Test
+        @DisplayName("当 propertyPath 不为空时，不自动解析 JSON 字符串")
+        void shouldReturnNullGivenPropertyPathIsNotEmpty() {
+            Object actual = FastJsonValueFetcherTest.this.fetcher.fetch(this.object, "k1.k2");
+            assertThat(actual).isNull();
+        }
+    }
+
     @Nested
     @DisplayName("当 object 为键值对时")
     class GivenObjectIsKeyValuePair {

framework/fit/java/fit-builtin/plugins/fit-value-fastjson/src/test/java/modelengine/fit/value/fastjson/FastJsonValueSetterTest.java

@@ -1,8 +1,8 @@
-/*---------------------------------------------------------------------------------------------
- *  Copyright (c) 2024 Huawei Technologies Co., Ltd. All rights reserved.
- *  This file is a part of the ModelEngine Project.
- *  Licensed under the MIT License. See License.txt in the project root for license information.
- *--------------------------------------------------------------------------------------------*/
+/*
+ * Copyright (c) 2024-2025 Huawei Technologies Co., Ltd. All rights reserved.
+ * This file is a part of the ModelEngine Project.
+ * Licensed under the MIT License. See License.txt in the project root for license information.
+ */
 
 package modelengine.fit.value.fastjson;
 
@@ -71,6 +71,29 @@ void shouldReturnReplacedValueGivenPropertyPathIsEmpty() {
         }
     }
 
+    @Nested
+    @DisplayName("当 object 为 JSON 字符串时")
+    class GivenObjectIsJsonString {
+        private Object object;
+
+        @BeforeEach
+        void setup() {
+            this.object = "{\"k1\":{\"k2\":\"v\"}}";
+        }
+
+        @AfterEach
+        void teardown() {
+            this.object = null;
+        }
+
+        @Test
+        @DisplayName("当 propertyPath 不为空时，不自动解析 JSON 字符串")
+        void shouldReturnOriginalStringGivenPropertyPathIsNotEmpty() {
+            Object actual = FastJsonValueSetterTest.this.setter.set(this.object, "k1.k2", "v1");
+            assertThat(actual).isEqualTo(this.object);
+        }
+    }
+
     @Nested
     @DisplayName("当 object 为键值对时")
     class GivenObjectIsKeyValuePair {