How and When Does a JSESSIONID Cookie Get Created?

When and How is a JSESSIONID Created?

A unique JSESSIONID cookie is generated when a session is established. This occurs when the code invokes request.getSession() or request.getSession(true) for the first time. Noteworthy, using request.getSession(false) retrieves the session without creating a new one if it doesn't exist; thus, no cookie is sent.

Session Scope

Sessions are confined to the context of the specific web application deployed on the server. Even if multiple web applications share the same domain and use the same container mechanism (e.g., cookie), the session objects and attributes within them remain isolated per-context. This behavior strictly aligns with the Servlet 2.4 specification, which explicitly states that sessions are "scoped at the application (or servlet context) level," and that any underlying mechanism shared across contexts must remain separate and distinct.

As an additional note, visiting a JSP page without an existing session will automatically generate a new one by default. However, you can disable this behavior by using the session='false' page directive, which prevents the session variable from being accessible on the JSP page.

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