fix: decode node IDs as string in ClientCallable methods

src/main/java/com/flowingcode/vaadin/addons/orgchart/OrgChart.java

@@ -383,6 +383,28 @@ private List<Integer> convertJsonArrayToIntegerList(JsonArray jsonIds) {
     return idList;
   }
 
+  /**
+   * Converts a comma-separated string of numeric IDs to a JsonArray.
+   * <p>
+   * IDs are received from the client as a string because {@code String} is the only argument type
+   * that every supported Vaadin version is able to decode for a {@link ClientCallable} method: up
+   * to Vaadin 24 the RPC decoder only accepts {@code String}, {@code Boolean}, {@code Integer},
+   * {@code Double} and {@code elemental.json.JsonValue}, while Vaadin 25 decodes with Jackson and
+   * no longer knows about {@code elemental.json}.
+   *
+   * @param ids comma-separated numeric IDs, possibly empty or {@code null}
+   * @return the IDs as a JsonArray of numbers
+   */
+  private JsonArray convertIdsToJsonArray(String ids) {
+    JsonArray jsonIds = Json.createArray();
+    if (ids != null && !ids.isEmpty()) {
+      for (String id : ids.split(",")) {
+        jsonIds.set(jsonIds.length(), Double.parseDouble(id.trim()));
+      }
+    }
+    return jsonIds;
+  }
+
   /**
    * Appends a list of items to a parent node's children list.
    * 
@@ -436,14 +458,27 @@ public void addSiblings(Integer nodeId, List<OrgChartItem> siblings) {
   }
 
 
+  /**
+   * Bridge for {@link #onSiblingsAdded(String, JsonArray)}, invoked from the client side. The IDs
+   * are received as a comma-separated string, since {@code JsonArray} arguments cannot be decoded
+   * by all supported Vaadin versions.
+   *
+   * @param nodeId the ID of the node that received new siblings
+   * @param siblingIds comma-separated IDs for the newly added siblings
+   * @see #convertIdsToJsonArray(String)
+   */
+  @ClientCallable
+  private void onSiblingsAdded(String nodeId, String siblingIds) {
+    onSiblingsAdded(nodeId, convertIdsToJsonArray(siblingIds));
+  }
+
   /**
    * Handles sibling addition events from the client side. Converts the received JsonArray of
    * sibling IDs to a List and fires a {@link SiblingsAddedEvent}.
    *
    * @param nodeId the ID of the node that received new siblings
    * @param siblingIds array of IDs for the newly added siblings
    */
-  @ClientCallable
   private void onSiblingsAdded(String nodeId, JsonArray siblingIds) {
     // Find the node where siblings were added
     OrgChartItem targetItem = getById(Integer.valueOf(nodeId), orgChartItem);
@@ -518,7 +553,20 @@ public void addChildren(Integer nodeId, List<OrgChartItem> children) {
     }
   }
 
+  /**
+   * Bridge for {@link #onChildrenAdded(String, JsonArray)}, invoked from the client side. The IDs
+   * are received as a comma-separated string, since {@code JsonArray} arguments cannot be decoded
+   * by all supported Vaadin versions.
+   *
+   * @param nodeId the ID of the parent node that received new children
+   * @param childIds comma-separated IDs for the newly added children
+   * @see #convertIdsToJsonArray(String)
+   */
   @ClientCallable
+  private void onChildrenAdded(String nodeId, String childIds) {
+    onChildrenAdded(nodeId, convertIdsToJsonArray(childIds));
+  }
+
   private void onChildrenAdded(String nodeId, JsonArray childIds) {
     // Find the parent node where children were added
     OrgChartItem parentItem = getById(Integer.valueOf(nodeId), orgChartItem);

src/main/resources/META-INF/frontend/fc-orgchart.js

@@ -169,7 +169,7 @@ class FCOrgChart extends PolymerElement {
 
                 // Notify server about siblings added with just the IDs
                 const siblingIds = siblingsData.map(sibling => sibling.id);
-                this.$server.onSiblingsAdded(nodeId, siblingIds);
+                this.$server.onSiblingsAdded(nodeId, siblingIds.join(','));
             }
         }
     }
@@ -190,7 +190,7 @@ class FCOrgChart extends PolymerElement {
 				this._chartInstance.addChildren($node, childrenData);		
 				// Notify server about children added with just the IDs
 				const childIds = childrenData.map(child => child.id);
-				this.$server.onChildrenAdded(nodeId, childIds);
+				this.$server.onChildrenAdded(nodeId, childIds.join(','));
 			}
 		}
 	}