Error Handling, Retries, Dead Letter Channel, and onException
Learn how Camel handles failures and how to design routes that behave predictably under operational stress.
Inside this chapter
- Why Error Handling Is Central
- Dead Letter Channel
- onException
- Operational Mindset
Series navigation
Study the chapters in order for the clearest path from Camel basics to advanced route design and production operations. Use the navigation at the bottom of each page to move through the full series.
Why Error Handling Is Central
Integration systems fail in many ways: network timeouts, invalid payloads, unavailable downstream systems, broker outages, file-lock issues, and business validation errors. A good Camel route is not only about the happy path. It is also about predictable failure behavior.
Dead Letter Channel
errorHandler(deadLetterChannel("jms:queue:dead")
.maximumRedeliveries(3)
.redeliveryDelay(2000));The dead letter channel is a common strategy for moving failed messages aside after retries are exhausted, instead of losing them silently.
onException
onException(Exception.class)
.handled(true)
.to("log:error")
.to("jms:queue:failedMessages");This lets teams define special behavior for exceptions without cluttering business routes with repeated try-catch style thinking.
Operational Mindset
Advanced integration design asks: what happens when the downstream system is slow, what gets retried, what gets parked, what gets alerted, and what can be safely replayed later? Camel gives tools for these questions, but architects must still decide wisely.