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This is the new default error handler in Camel 2.0 onwards.

This error handler have a limited set of features. You can use the Exception Clause to catch exceptions and De Tour exchanges. Redeliveries is not supports, so any redelivery configuration on an Exception Clause will not apply.

It has the same power as the Dead Letter Channel, however it does not support a dead letter queue, which is the only difference between the two of them.

The DefaultErrorHandler is configured differently that Dead Letter Channel as it is configured to:

• not redeliver
• not handled
• no dead letter queue (not possible)

By default, By default any exception thrown during routing will be propagated back to the caller and the Exchange ends immediately. However, you can use the Exception Clause to catch a given exception and lower the exception by marking it as handled. If so, the exception will not be sent back to the caller, and the Exchange continues to be routed.

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In this route below, any exception thrown in, eg the validateOrder bean, will be propagated back to the caller , and its via the jetty endpoint. It will return a an HTTP error message back to the client.

from("jetty:http://localhost/myservice/order").to("bean:validateOrder").to("jms:queue:order");

We can add a an onException in case we want to catch certains certain exceptions and route them differently, for instance to catch a ValidationException and return a fixed response to the caller.

onException(ValidationException.class).handled(true).transform(body(constant("INVALID ORDER")));

from("jetty:http://localhost/myservice/order").to("bean:validateOrder").to("jms:queue:order");

When the ValidationException is thrown from the validate order validateOrder bean, it is intercepted by the DefaultErrorHandler and it let that lets the onException(ValidationException.class) handle it, so the Exchange is routed to this onException route, and since we use handled(true), then the original exception is lowered (= cleared) , and we transform the message into a fixed response that are is returned to jetty endpoint that returns it to the original caller.

See Also

• Error Handler
• Dead Letter Channel