JSPs have access to beans bound to the various scoped objects. In older versions you had to use the <jsp:useBean .. /> tag in order to define a reference. In newer versions, you can reference them with EL regardless of the scope to which they're bound.
Any JSP tutorial worth it's salt covers access to scoped objects.
I need a way to "despatch" a bean when sending a JSP back to the client.
You do know that you don't 'send' a JSP to the client, right? When you forward or redirect to a JSP, it's executed on the server and the resulting text is streamed to the client. Depending on whether you forward with a requestDispatcher or use response.sendRedirect, you will have different limits as far as what scoped objects you can bind your beans to.