Allow retaining null-valued bean properties in JSONObjects

src/main/java/org/json/JSONObject.java

@@ -401,12 +401,17 @@ private JSONObject(Map<?, ?> m, int recursionDepth, JSONParserConfiguration json
      */
     public JSONObject(Object bean) {
         this();
-        this.populateMap(bean);
+        this.populateMap(bean, new JSONParserConfiguration());
+    }
+
+    public JSONObject(Object bean, JSONParserConfiguration jsonParserConfiguration) {
+        this();
+        this.populateMap(bean, jsonParserConfiguration);
     }
 
     private JSONObject(Object bean, Set<Object> objectsRecord) {
         this();
-        this.populateMap(bean, objectsRecord);
+        this.populateMap(bean, objectsRecord, new JSONParserConfiguration());
     }
 
     /**
@@ -1764,11 +1769,11 @@ public String optString(String key, String defaultValue) {
      * @throws JSONException
      *            If a getter returned a non-finite number.
      */
-    private void populateMap(Object bean) {
-        populateMap(bean, Collections.newSetFromMap(new IdentityHashMap<Object, Boolean>()));
+    private void populateMap(Object bean, JSONParserConfiguration jsonParserConfiguration) {
+        populateMap(bean, Collections.newSetFromMap(new IdentityHashMap<Object, Boolean>()), jsonParserConfiguration);
     }
 
-    private void populateMap(Object bean, Set<Object> objectsRecord) {
+    private void populateMap(Object bean, Set<Object> objectsRecord, JSONParserConfiguration jsonParserConfiguration) {
         Class<?> klass = bean.getClass();
 
         // If klass is a System class then set includeSuperClass to false.
@@ -1788,7 +1793,7 @@ && isValidMethodName(method.getName())) {
                 if (key != null && !key.isEmpty()) {
                     try {
                         final Object result = method.invoke(bean);
-                        if (result != null) {
+                        if (result != null || jsonParserConfiguration.isUseNativeNulls()) {
                             // check cyclic dependency and throw error if needed
                             // the wrap and populateMap combination method is
                             // itself DFS recursive

src/test/java/org/json/junit/JSONObjectTest.java

@@ -4011,5 +4011,37 @@ public static HashMap<String, Object> buildNestedMap(int maxDepth) {
         nestedMap.put("t", buildNestedMap(maxDepth - 1));
         return nestedMap;
     }
+
+
+    /**
+     * Tests the behavior of the {@link JSONObject} when parsing a bean with null fields
+     * using a custom {@link JSONParserConfiguration} that enables the use of native nulls.
+     * 
+     * <p>This test ensures that uninitialized fields in the bean are serialized correctly
+     * into the resulting JSON object, and their keys are present in the JSON string output.</p>
+     */
+    @Test
+    public void jsonObjectParseNullFieldsWithParserConfiguration() {
+        JSONParserConfiguration jsonParserConfiguration = new JSONParserConfiguration();
+        RecursiveBean bean = new RecursiveBean(null);
+        JSONObject jsonObject = new JSONObject(bean, jsonParserConfiguration.withUseNativeNulls(true));
+        assertTrue("name key should be present", jsonObject.has("name"));
+        assertTrue("ref key should be present", jsonObject.has("ref"));
+        assertTrue("ref2 key should be present", jsonObject.has("ref2"));
+    }
+
+    /**
+     * Tests the behavior of the {@link JSONObject} when parsing a bean with null fields
+     * without using a custom {@link JSONParserConfiguration}.
+     * 
+     * <p>This test ensures that uninitialized fields in the bean are not serialized
+     * into the resulting JSON object, and the object remains empty.</p>
+     */
+    @Test
+    public void jsonObjectParseNullFieldsWithoutParserConfiguration() {
+        RecursiveBean bean = new RecursiveBean(null);
+        JSONObject jsonObject = new JSONObject(bean);
+        assertTrue("JSONObject should be empty", jsonObject.isEmpty());
+    }
 
 }