I'm developing a simple app with WebSockets. Client side you can send input texts, while the server side is implemented via a Java class with annotated as ServerEndpoint. Here the input texts received get decoded and sent to all of the open sessions.
This works, but I want to store every message received by the server, so that when a new client connects, (using a method annotated with @OnOpen) it receives all the messages that has been sent while he was "offline". Where can I store this messages without using a database?