How to create a long lived cassandra CqlSession in a Javalin app

Question

I have an app built with Javalin (a simple HTTP framework in Java) that leverages Cassandra as the backend.

According to Datastax docs https://docs.datastax.com/en/developer/java-driver/4.9/manual/core/#quick-start

CqlSession is the main entry point of the driver. It holds the known state of the actual Cassandra cluster, and is what you use to execute queries. It is thread-safe, you should create a single instance (per target Cassandra cluster), and share it throughout your application;

This is what my main function looks like:

  public static void main(String[] args) {
    CqlSession cqlSession = CqlSession.builder().build();
    runCassandraMigration(cqlSession);
    Javalin app =
        Javalin.create(config -> config.registerPlugin(new OpenApiPlugin(getOpenApiOptions())))
            .start(PORT);
    Handlers handlers = new Handlers(cqlSession);
    registerAppRoutes(app, handlers);
  }

The Handlers class include handle function like below:

public class Handlers {
  private final CqlSession session;
  
  public Context getAllUsers(Context ctx) {
    ResultSet rs = session.execute("select * from my_status.users");
    List<Row> rows = rs.all();
    return ctx.json(rows.stream().map(this::rowToUser).collect(Collectors.toList()));
  }
}

However, after I start the application, and hit the REST endpoint locally, I got

java.lang.IllegalStateException: Session is closed

I want to know how to create a long-lived CqlSession rather than per-request short-lived ones. The app I am working on can be found in https://github.com/YikSanChan/mystatus/tree/main/api/src/main/java.