Json Navigation: Use NULL as a placeholder. (#354)

Author: SimY4

xpath-to-json-gson/src/main/java/com/github/simy4/xpath/gson/navigator/GsonNavigator.java

@@ -22,6 +22,7 @@
 import com.github.simy4.xpath.navigator.Navigator;
 import com.google.gson.JsonArray;
 import com.google.gson.JsonElement;
+import com.google.gson.JsonNull;
 import com.google.gson.JsonObject;
 import com.google.gson.JsonPrimitive;
 
@@ -181,7 +182,7 @@ private GsonByIndexNode prependToArray(
     parentArray.add(arrayElement);
     while (elementToCopy != arrayElement && i > 0) {
       arrayElement = parentArray.get(i - 1);
-      parentArray.set(i, arrayElement);
+      parentArray.set(i, JsonNull.INSTANCE);
       i -= 1;
     }
     return new GsonByIndexNode(i, parent);

xpath-to-json-jackson/src/main/java/com/github/simy4/xpath/jackson/navigator/JacksonNavigator.java

@@ -18,6 +18,7 @@
 import com.fasterxml.jackson.databind.JsonNode;
 import com.fasterxml.jackson.databind.node.ArrayNode;
 import com.fasterxml.jackson.databind.node.JsonNodeFactory;
+import com.fasterxml.jackson.databind.node.NullNode;
 import com.fasterxml.jackson.databind.node.ObjectNode;
 import com.fasterxml.jackson.databind.node.TextNode;
 import com.github.simy4.xpath.XmlBuilderException;
@@ -183,7 +184,7 @@ private JacksonByIndexNode prependToArray(
     parentArray.add(arrayNode);
     while (nodeToCopy != arrayNode && i > 0) {
       arrayNode = parentArray.get(i - 1);
-      parentArray.set(i, arrayNode);
+      parentArray.set(i, NullNode.instance);
       i -= 1;
     }
     return new JacksonByIndexNode(i, parent);

xpath-to-json-jakarta/src/main/java/com/github/simy4/xpath/json/navigator/JakartaJsonNavigator.java

@@ -197,7 +197,7 @@ private JakartaJsonNode appendToArray(JakartaJsonNode parent, QName name, JsonAr
   private JakartaJsonByIndexNode prependToArray(
       JakartaJsonNode parent, JsonValue valueToCopy, JsonArray parentArray) {
     final int index = parentArray.indexOf(valueToCopy);
-    parentArray = jsonProvider.createArrayBuilder(parentArray).add(index, valueToCopy).build();
+    parentArray = jsonProvider.createArrayBuilder(parentArray).add(index, JsonValue.NULL).build();
     parent.set(jsonProvider, parentArray);
     return new JakartaJsonByIndexNode(index, parent);
   }

xpath-to-json-json/src/main/java/com/github/simy4/xpath/json/navigator/JsonJsonNavigator.java

@@ -177,7 +177,7 @@ private JsonJsonByIndexNode prependToArray(
     parentArray.put(arrayElement);
     while (valueToCopy != arrayElement && i > 0) {
       arrayElement = parentArray.get(i - 1);
-      parentArray.put(i, arrayElement);
+      parentArray.put(i, JSONObject.NULL);
       i -= 1;
     }
     return new JsonJsonByIndexNode(i, parent);