Do you really want to store serialized Java objects on a JMS queue? Then you have a strong dependency on the class, from the consumer as well, as they would need to have that Class on their classpath etc.
Maybe you can just store the JSON on the queue instead? Then its even human readable.
That said you can configure the jmsMessageType=Object on the JMS endpoint to tell Camel to use javax.jms.ObjectMessage as the JMS type.