BAEL-9456 (#18835)

* BAEL-9456

* BAEL-9456

Author: Neetika23

json-modules/gson-3/src/main/java/com/baeldung/gson/json/JsonKeyExtractor.java

@@ -0,0 +1,32 @@
+package com.baeldung.gson.json;
+
+import com.google.gson.JsonElement;
+import com.google.gson.JsonObject;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Set;
+
+public class JsonKeyExtractor {
+
+    public static List<String> getAllKeys(JsonObject jsonObject) {
+        List<String> keys = new ArrayList<>();
+        extractKeys("", jsonObject, keys);
+        return keys;
+    }
+
+    private static void extractKeys(String prefix, JsonObject jsonObject, List<String> keys) {
+        Set<String> jsonKeys = jsonObject.keySet();
+
+        for (String key : jsonKeys) {
+            String fullKey = prefix.isEmpty() ? key : prefix + "." + key;
+            keys.add(fullKey);
+
+            JsonElement element = jsonObject.get(key);
+
+            if (element.isJsonObject()) {
+                extractKeys(fullKey, element.getAsJsonObject(), keys);
+            }
+        }
+    }
+}

json-modules/gson-3/src/test/java/com/baeldung/gson/json/JsonKeyExtractorUnitTest.java

@@ -0,0 +1,57 @@
+package com.baeldung.gson.json;
+
+import com.google.gson.JsonObject;
+import com.google.gson.JsonParser;
+import org.junit.jupiter.api.Test;
+
+import java.util.List;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+public class JsonKeyExtractorUnitTest {
+
+    @Test
+    void givenJson_whenTopLevelKeys_thenGetAllKeys() {
+        String json = "{ \"name\":\"Henry\", \"email\":\"[email protected]\", \"age\":25 }";
+        JsonObject jsonObject = JsonParser.parseString(json).getAsJsonObject();
+        List<String> keys = JsonKeyExtractor.getAllKeys(jsonObject);
+
+        assertEquals(3, keys.size());
+        assertTrue(keys.contains("name"));
+        assertTrue(keys.contains("email"));
+        assertTrue(keys.contains("age"));
+    }
+
+    @Test
+    void givenJson_whenNestedKeys_thenGetAllKeys() {
+        String json = "{ \"address\": { \"city\":\"New York\", \"zip\":\"10001\" } }";
+        JsonObject jsonObject = JsonParser.parseString(json).getAsJsonObject();
+        List<String> keys = JsonKeyExtractor.getAllKeys(jsonObject);
+
+        assertEquals(3, keys.size());
+        assertTrue(keys.contains("address"));
+        assertTrue(keys.contains("address.city"));
+        assertTrue(keys.contains("address.zip"));
+    }
+
+    @Test
+    void givenJson_whenEmpty_thenGetNoKeys() {
+        String json = "{}";
+        JsonObject jsonObject = JsonParser.parseString(json).getAsJsonObject();
+        List<String> keys = JsonKeyExtractor.getAllKeys(jsonObject);
+
+        assertTrue(keys.isEmpty());
+    }
+
+    @Test
+    void givenJson_whenDeeplyNestedKeys_thenGetAllKeys() {
+        String json = "{ \"user\": { \"profile\": { \"contacts\": { \"email\": \"[email protected]\" } } } }";
+        JsonObject jsonObject = JsonParser.parseString(json).getAsJsonObject();
+        List<String> keys = JsonKeyExtractor.getAllKeys(jsonObject);
+
+        assertTrue(keys.contains("user"));
+        assertTrue(keys.contains("user.profile"));
+        assertTrue(keys.contains("user.profile.contacts"));
+        assertTrue(keys.contains("user.profile.contacts.email"));
+    }
+}