Vaadin 25 is based on Jackson instead of JSON elemental, which requires minor changes here https://github.com/FlowingCode/CommonsDemo/blob/77d981eda0cf25d15c50edf8043b6b1aa8260172/src/main/java/com/flowingcode/vaadin/addons/demo/SourceCodeViewer.java#L88 and here https://github.com/FlowingCode/CommonsDemo/blob/77d981eda0cf25d15c50edf8043b6b1aa8260172/src/main/java/com/flowingcode/vaadin/addons/demo/MultiSourceCodeViewer.java#L49