使用拦截器时的骆驼异常处理行为

Question

In a unit test I want to simulate that an Exception occurs.

I expect to receive one message at the "mock:count" endpoint, because of the doTry/doCatch -block. Why is this not happening and why is the Exception handled by the general onException -block?

import org.apache.camel.LoggingLevel;
import org.apache.camel.builder.AdviceWithRouteBuilder;
import org.apache.camel.builder.RouteBuilder;
import org.apache.camel.component.mock.MockEndpoint;
import org.apache.camel.test.junit4.CamelTestSupport;
import org.apache.cxf.binding.soap.SoapFault;
import org.junit.Test;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Text;

public class TestClass extends CamelTestSupport {
   @Override
   protected RouteBuilder createRouteBuilder() throws Exception {
      return new RouteBuilder() {
         @Override
         public void configure() throws Exception {
            onException(Exception.class)
                  .log(LoggingLevel.INFO, "outer catch")
                  .handled(true);

            from("direct:start")
                  .doTry()
                     .to("mock:exception")

                  .doCatch(Exception.class)
                     .log(LoggingLevel.INFO, "inner catch")
                     .to("mock:count")
                  .end();
         }
      };
   }

   @Test
   public void testBlaat() throws Exception {
      final SoapFault soapFault = new SoapFault("Something clearly went wrong", SoapFault.FAULT_CODE_CLIENT);
      Element detail = soapFault.getOrCreateDetail();
      Document doc = detail.getOwnerDocument();
      Text tn = doc.createTextNode("Fault details");
      detail.appendChild(tn);

      context.getRouteDefinitions().get(0).adviceWith(context, new AdviceWithRouteBuilder() {
         @Override
         public void configure() throws Exception {
            interceptSendToEndpoint("mock:exception").throwException(new Exception("test"));
         }
      });

      template.sendBody("direct:start", "start");

      MockEndpoint endpoint = getMockEndpoint("mock:count");
      endpoint.expectedMessageCount(1);

      assertMockEndpointsSatisfied();

   }
}

Answer 1

It turns out that exceptions thrown from an AdviceWithRouteBuilder are not seen by the RouteDefinition 's doTry/doCatch when the route is intercepted by the AdviceWithRouteBuilder because they are on different channels. The way to solve this is to use a mock for the endpoint and throw the exception from the mock:

getMockEndpoint("mock:exception").whenAnyExchangeReceived(new 
Processor() { 

            @Override 
            public void process(Exchange exchange) throws Exception { 
                throw new Exception("fail me"); 
            } 
        });

See: http://camel.465427.n5.nabble.com/question-about-exception-handling-behavior-td5743489.html

Also see this issue on JIRA: https://issues.apache.org/jira/browse/CAMEL-6300 It is fixed in Camel 2.10.5 and other newer versions.

Answer 2

I am not sure why this is happening to you, but I have an idea. I am thinking that your context is starting before reaching your test case and maybe your interceptor is being set up too late. Can you try the following?

Add this method:

@Override
public boolean isUseRouteBuilder() {
    return false;
}

Then use the regular way of defining the route with context.addRoutes(new RouteBuilder(){ .. }) instead of overriding createRouteBuilder . Also, define your interceptor here.

And after configuring your route and interceptor run context.start() in your test case. Try and let me know if it worked.

UPDATE : Overriding isUseRouteBuilder is not required.

UPDATE2:

I have been running few tests and I am seeing the same behavior. It seems that onException always triggers before doCatch. Also, if you set handled to true the exception does not get propagated and does not reach the doCatch block.

Based on the documentation of doTry doCatch doFinally I would understand the error handler does not apply ( When using doTry .. doCatch .. doFinally then the regular Camel Error Handler does not apply ) but it seems the error handler and the onException are not the same.

Also, I have found this: how to handle exception or fault in multiple routes which could be helpful for you.

One last thing: you can define your interceptor in the same RouteBuilder:

    context.addRoutes(new RouteBuilder() {
        @Override
        public void configure() throws Exception {
            interceptSendToEndpoint("mock:exception").throwException(new Exception());

            onException(Exception.class).process(new Processor() {
                @Override
                public void process(Exchange exchange) throws Exception {
                    System.out.println("from onException");

                }

            }).handled(false);

            from("direct:start")
            //.errorHandler(noErrorHandler())
            .doTry()
                .to("mock:exception")
            .doCatch(Exception.class)
                .process(new Processor() {
                   @Override
                   public void process(Exchange exchange) throws Exception {
                       System.out.println("from doCatch");
                   }
                })
                .to("mock:count")
            .end();


        }
    });

Does this help?