Apache Camel: How to get the exception message inside the doCatch() block? - apache

Question

I need to return the message from a thrown exception, or put it in the outmessage. But it does not print the correct message on the frontend.
The camel docs suggest using .transform(simple?...) .handled(true) but most of it is deprecated.
What's the correct way of doing this?
Response:
<418 I'm a teapot,simple{${exception.message}},{}>
Route
from("direct:csv")
.doTry()
.process(doSomeThingWithTheFileProcessor)
.doCatch(Exception.class)
.process(e -> {
e.getOut().setBody(new ResponseEntity<String>(exceptionMessage().toString(), HttpStatus.I_AM_A_TEAPOT));
}).stop()
.end()
.process(finalizeTheRouteProcessor);
doSomethingWithFileProcessor
public void process(Exchange exchange) throws Exception {
String filename = exchange.getIn().getHeader("CamelFileName", String.class);
MyFile mf = repo.getFile(filename); //throws exception
exchange.getOut().setBody(exchange.getIn().getBody());
exchange.getOut().setHeader("CamelFileName", exchange.getIn().getHeader("CamelFileName"));
}

Answer 1

There is a lot of ways how to do it. All of it is correct, choose your favourite depending on complexity of error handling. I have published examples in this gist. None of it is deprecated in Camel version 2.22.0.
With Processor
from("direct:withProcessor")
.doTry()
.process(new ThrowExceptionProcessor())
.doCatch(Exception.class)
.process(new Processor() {
#Override
public void process(Exchange exchange) throws Exception {
final Throwable ex = exchange.getProperty(Exchange.EXCEPTION_CAUGHT, Throwable.class);
exchange.getIn().setBody(ex.getMessage());
}
})
.end();
With Simple language
from("direct:withSimple")
.doTry()
.process(new ThrowExceptionProcessor())
.doCatch(Exception.class)
.transform().simple("${exception.message}")
.end();
With setBody
from("direct:withValueBuilder")
.doTry()
.process(new ThrowExceptionProcessor())
.doCatch(Exception.class)
.setBody(exceptionMessage())
.end();

Answer 2

In the doCatch() Camel moves the exception into a property on the exchange with the key Exchange.EXCEPTION_CAUGHT (http://camel.apache.org/why-is-the-exception-null-when-i-use-onexception.html).
So you can use
e.getOut().setBody(new ResponseEntity<String>(e.getProperty(Exchange.EXCEPTION_CAUGHT, Exception.class).getMessage(), HttpStatus.OK));