Question

Is there any embedded persistence solution shipped with Camel API? I want to save my dead letter messages. It can be done through DB or JMS queue but I want to avoid it while shipping to clients.
I read about HawtDB in ‘Camel In Action’. But it seems to be tightly coupled with Aggregator EIP.
Later i want to create a report on all the dead letter messages and show it to Client.

Answer 1

You can just use any persistence component to save your dead letter messages (Hibernate, JPA, JDBC, DB4O, etc.). In case of majority of persistence components you will not save the message itself, but selected (meta)data from it (the notable exception from that is the case of using DB4O component).

For example if you’re sending Hibernates entities in messages, you can use Hibernate component:

from("seda:deadMessageStore").
  setBody().groovy("new DeadMessageLog(request.headers, request.body) ").
  to("hibernate:com.foo.DeadMessageLog");
errorHandler(deadLetterChannel("seda:deadMessageStore"));

If you cannot predict what kind of classes will you send to the dead letter queue, consider using DB4O component. DB4O is extremely flexible in that matter since it allows you to store any Java object in the your queue (without explicit mapping, like in the case of the Hibernate or JPA).

// store any Java object without transformations
errorHandler(deadLetterChannel("db4o:java.lang.Object"))

Also creating embedded DB40 container is very simple:

ObjectContainer db = Db4oEmbedded.openFile(Db4oEmbedded.newConfiguration(), DB4OFILENAME);