Integration / Apache Camel Interview Questions
What is a CamelContext and what is its lifecycle (start, stop, suspend, resume)?
The CamelContext is the central runtime container for a Camel application. It owns all routes, components, endpoints, type converters, the bean registry, data formats, and thread pools. Its lifecycle controls when routes are active and messages can flow.
| State | Method | What happens |
|---|---|---|
| Created | new DefaultCamelContext() | Object instantiated; no routes running. |
| Starting | context.start() | Components initialised; consumer endpoints begin polling. |
| Started | — | All routes active; messages flowing normally. |
| Suspending | context.suspend() | Consumers stop accepting; in-flight exchanges drain gracefully. |
| Suspended | — | Paused — useful for zero-downtime maintenance windows. |
| Resuming | context.resume() | Consumers reactivated. |
| Stopping | context.stop() | Graceful shutdown; thread pools terminated. |
| Stopped | — | Terminal state — create a new instance to restart. |
CamelContext ctx = new DefaultCamelContext();
ctx.addRoutes(new MyRouteBuilder());
ctx.start();
ctx.suspend(); // pause consumers gracefully
ctx.resume(); // re-activate consumers
ctx.stop(); // full shutdownIn Spring Boot, the CamelContext lifecycle is tied to the ApplicationContext. Individual routes can be started or stopped via context.startRoute(id) and context.stopRoute(id) without affecting other running routes.
What is the key difference between suspending and stopping a CamelContext?
After calling context.stop(), can the same CamelContext be restarted?
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