Agones4J is a Java Game Server Client SDK for Agones (https://agones.dev/) that uses the exposed REST API of Agones
Here is a simple example of marking the GameServer as ready and then adding a label to it.
// Instantiate a new SDK with the default port and URL
AgonesSDK agones = new AgonesSDK();
// Mark the server as ready
agones.ready().thenAccept(success -> {
// Then add a label
agones.setLabel("my-label", "dummy").thenAccept(success2 -> {
System.out.println(success2 ? "Successfully set the label :D" : "It didn\'t work :(");
});
});