You can store state on the Camel Exchange as property. They will there for the entire lifecycle for that particular exchange while its being routed in Camel.

The RouteBuilder is used to create the route model to the actual runtime route and as such there is only one instance of it.

You can access the properties on the Exchange from a Camel processor

public void process(Exchange exchange) throws Exception {
   String foo = (String) exchange.getProperty("myFoo");
   ...
   exchange.setProperty("myFoo", updatedValue);
}