Consider a use-case where a message has some content (say a list of IDs) that we want to transform into a list of objects retrieved from the database. One could do this by using the camel-sql component as a producer. However, I don't think there's good way to do this using the camel-jpa component.
As a producer, camel-jpa does not support named-queries. We have some places where we use JPA over some tables, but in use-cases like this, we switch to camel-sql for that step, or code a processer. Workable, but a slight impedance mis-match.
It would be nice to add support for named-query (and related options) to the producer in camel-jpa.