例外条款

onException(IOException.class)
    .maximumRedeliveries(3);

onException(OrderFailedException.class)
    .maximumRedeliveries(2);

onException(IOException.class)
    .maximumRedeliveries(3);

onException(OrderFailedException.class)
    .maximumRedeliveries(2);

onException(FileNotFoundException.class)
    .handled(true)
    .to("log:nofile");

onException(ConnectException.class)
    .from("direct:start")
    .process("processor1")
    .process("processor2") // <--- throws a ConnectException
    .to("mock:theEnd")

<bean id="myRedeliveryPolicy" class="org.apache.camel.processor.RedeliveryPolicy">
    <property name="maximumRedeliveries" value="${myprop.max}"/>
</bean>

<!-- here we reference our redelivery policy defined above -->
<onException redeliveryPolicyRef="myRedeliveryPolicy">
    <!-- you can define multiple exceptions just adding more exception elements as show below -->
    <exception>com.mycompany.MyFirstException</exception>
    <exception>com.mycompany.MySecondException</exception>
</onException>

onException(MyBusinessException.class, MyOtherBusinessException.class)
    .maximumRedeliveries(2)
    .to("activemq:businessFailed");

<onException>
    <exception>com.mycompany.MyBusinessException</exception>
    <exception>com.mycompany.MyOtherBusinessException</exception>
    <redeliveryPolicy maximumRedeliveries="2"/>
    <to uri="activemq:businessFailed"/>
</onException>

// here we register exception cause for MyFunctionException
// when this exception occurs we want it to be processed by our
// processor
onException(MyFunctionalException.class)
  .process(new MyFunctionFailureHandler())
  .stop();

    public static class MyFunctionFailureHandler implements Processor {

        @Override
        public void process(Exchange exchange) throws Exception {
            // the caused by exception is stored in a property on the exchange
            Throwable caused = exchange.getProperty(Exchange.EXCEPTION_CAUGHT, Throwable.class);
            assertNotNull(caused);
            // here you can do what you want, but Camel regards this exception as
            // handled, and this processor as a failure handler, so it won't do redeliveries.
            // So this is the end of this route.
        }
    }

onException(ValidationException)
    .handled(true);

    // we do special error handling for when OrderFailedException is
    // thrown
    onException(OrderFailedException.class)
        // we mark the exchange as handled so the caller doesn't
        // receive the
        // OrderFailedException but whatever we want to return
        // instead
        .handled(true)
        // this bean handles the error handling where we can
        // customize the error
        // response using java code
        .bean(OrderService.class, "orderFailed")
        // and since this is an unit test we use mocks for testing
        .to("mock:error");

    // this is just the generic error handler where we set the
    // destination
    // and the number of redeliveries we want to try
    errorHandler(deadLetterChannel("mock:error").maximumRedeliveries(1));

    // this is our route where we handle orders
    from("direct:start")
        // this bean is our order service
        .bean(OrderService.class, "handleOrder")
        // this is the destination if the order is OK
        .to("mock:result");

    /**
     * Order service as a plain POJO class
     */
    public static class OrderService {

        /**
         * This method handle our order input and return the order
         */
        public Object handleOrder(@Headers Map headers, @Body String payload) throws OrderFailedException {
            headers.put("customerid", headers.get("customerid"));
            if ("Order: kaboom".equals(payload)) {
                throw new OrderFailedException("Cannot order: kaboom");
            } else {
                headers.put("orderid", "123");
                return "Order OK";
            }
        }

        /**
         * This method creates the response to the caller if the order could not
         * be processed
         */
        public Object orderFailed(@Headers Map headers, @Body String payload) {
            headers.put("customerid", headers.get("customerid"));
            headers.put("orderid", "failed");
            return "Order ERROR";
        }
    }

    public static class OrderFailedException extends Exception {

        private static final long serialVersionUID = 1L;

        public OrderFailedException(String message) {
            super(message);
        }

    }

 <!-- setup our error handler as the deal letter channel -->
<bean id="errorHandler" class="org.apache.camel.builder.DeadLetterChannelBuilder">
    <property name="deadLetterUri" value="mock:error"/>
</bean>

<!-- this is our POJO bean with our business logic defined as a plain spring bean -->
<bean id="orderService" class="org.apache.camel.spring.processor.onexception.OrderService" />

<!-- this is the camel context where we define the routes -->
<!-- define our error handler as a global error handler -->
<camelContext errorHandlerRef="errorHandler" xmlns="http://camel.apache.org/schema/spring">

  <onException>
    <!-- the exception is full qualified names as plain strings -->
    <!-- there can be more just add a 2nd, 3rd exception element (unbounded) -->
    <exception>org.apache.camel.spring.processor.onexception.OrderFailedException</exception>
    <!-- we can set the redelivery policy here as well -->
    <redeliveryPolicy maximumRedeliveries="1" />
    <!-- mark this as handled -->
    <handled>
      <constant>true</constant>
    </handled>
    <!-- let our order service handle this exception, call the orderFailed method -->
    <bean ref="orderService" method="orderFailed" />
    <!-- and since this is a unit test we use mock for assertions -->
    <to uri="mock:error" />
  </onException>

  <route>
    <!-- the route -->
    <from uri="direct:start" />
    <!-- in the normal route then route to our order service and call handleOrder method -->
    <bean ref="orderService" method="handleOrder" />
    <!-- and since this is a unit test we use mock for assertions -->
    <to uri="mock:result" />
  </route>

</camelContext>

// we catch MyFunctionalException and want to mark it as handled
// (= no failure returned to client)
// but we want to return a fixed text response, so we transform
// OUT body as Sorry.
onException(MyFunctionalException.class)
  .handled(true)
  .transform().constant("Sorry");

// we catch MyFunctionalException and want to mark it as handled
// (= no failure returned to client)
// but we want to return a fixed text response, so we transform
// OUT body and return the exception message
onException(MyFunctionalException.class)
  .handled(true)
  .transform(exceptionMessage());

// we catch MyFunctionalException and want to mark it as handled
// (= no failure returned to client)
// but we want to return a fixed text response, so we transform
// OUT body and return a nice message
// using the simple language where we want insert the exception
// message
onException(MyFunctionalException.class)
  .handled(true)
  .transform().simple("Error reported: ${exception.message} - cannot process this message.");

onException(IDontCareException.class)
    .continued(true);

from("jms:queue:order:input")
    .to("bean:validateOrder");
    .to("bean:transformOrder")
    .to("bean:handleOrder");

// will use original input message (body and headers)
onException(MyOrderException.class)
    .useOriginalMessage()
    .handled(true)
    .to("jms:queue:order:failed");

<onException useOriginalMessage="true">
    <exception>com.mycompany.MyOrderException</exception>
    <handled><constant>true</constant></handled>
    <to uri="jms:queue:order:failed"/>
</onException>

// will use original input body
onException(MyOrderException.class)
    .useOriginalBody()
    .handled(true)
    .to("jms:queue:order:failed");

from("jms:queue:order:input")
    .setHeader("application", constant("OrderApp"))
    .to("bean:validateOrder");
    .to("bean:transformOrder")
    .to("bean:handleOrder");

errorHandler(deadLetterChannel("mock:error").redeliveryDelay(0).maximumRedeliveries(3));

// here we define our onException to catch MyUserException when
// there is a header[user] on the exchange that is not null
onException(MyUserException.class).onWhen(header("user").isNotNull()).maximumRedeliveries(1)
    // setting delay to zero is just to make unit testing faster
    .redeliveryDelay(0).to(ERROR_USER_QUEUE);

// here we define onException to catch MyUserException as a kind
// of fallback when the above did not match.
// Notice: The order how we have defined these onException is
// important as Camel will resolve in the same order as they
// have been defined
onException(MyUserException.class).maximumRedeliveries(2)
    // setting delay to zero is just to make unit testing faster
    .redeliveryDelay(0).to(ERROR_QUEUE);

// when we redeliver caused by an IOException we want to do some
// special code before the redeliver attempt
onException(IOException.class)
    // try to redeliver at most 3 times
    .maximumRedeliveries(3)
    // setting delay to zero is just to make unit testing faster
    .redeliveryDelay(0).onRedelivery(new MyIORedeliverProcessor());

// This is our processor that is executed before every redelivery attempt
// here we can do what we want in the java code, such as altering the
// message
public static class MyRedeliverProcessor implements Processor {

    @Override
    public void process(Exchange exchange) throws Exception {
        // the message is being redelivered so we can alter it

        // we just append the redelivery counter to the body
        // you can of course do all kind of stuff instead
        String body = exchange.getIn().getBody(String.class);
        int count = exchange.getIn().getHeader("CamelRedeliveryCounter", Integer.class);

        exchange.getIn().setBody(body + count);
    }
}

<onException onRedeliveryRef="myIORedeliverProcessor">
    <exception>java.io.IOException</exception>
</onException>

 <bean id="myRedeliveryProcessor"
          class="org.apache.camel.processor.DeadLetterChannelOnExceptionOnRedeliveryTest$MyRedeliverProcessor"/>

// we want to use a predicate for retries so we can determine in
// our bean when retry should stop, notice it will overrule the global
// error handler where we defined at most 1 redelivery attempt. Here we will
// continue until the predicate returns false
onException(MyFunctionalException.class).retryWhile(method("myRetryHandler")).handled(true).transform().constant("Sorry");

public class MyRetryBean {

    // using bean binding we can bind the information from the exchange to
    // the types we have in our method signature
    public boolean retry(@Header(Exchange.REDELIVERY_COUNTER) Integer counter) {
        // NOTE: counter is the redelivery attempt, will start from 1
        // we can of course do what ever we want to determine the result but
        // this is a unit test so we end after 3 attempts
        return counter < 3;
    }
}

// configure the error handler to use my policy instead of the default from Camel
errorHandler(deadLetterChannel("mock:error").exceptionPolicyStrategy(new MyPolicy()));

public static class MyPolicy implements ExceptionPolicyStrategy {

    @Override
    public ExceptionPolicyKey getExceptionPolicy(Set<ExceptionPolicyKey> exceptionPolicies, Exchange exchange, Throwable exception) {
        // This is just an example that always forces the exception type configured
        // with MyPolicyException to win.
        return new ExceptionPolicyKey(null, MyPolicyException.class, null);
    }
}

<!-- setup our error handler as the deal letter channel -->
<bean id="errorHandler" class="org.apache.camel.builder.DeadLetterChannelBuilder">
    <property name="deadLetterUri" value="mock:error"/>
</bean>

<!-- this is our POJO bean with our business logic defined as a plain spring bean -->
<bean id="orderService" class="org.apache.camel.spring.processor.onexception.OrderService" />

<!-- this is the camel context where we define the routes -->
<!-- define our error handler as a global error handler -->
<camelContext errorHandlerRef="errorHandler" xmlns="http://camel.apache.org/schema/spring">

  <onException>
    <!-- the exception is full qualified names as plain strings -->
    <!-- there can be more just add a 2nd, 3rd exception element (unbounded) -->
    <exception>org.apache.camel.spring.processor.onexception.OrderFailedException</exception>
    <!-- we can set the redelivery policy here as well -->
    <redeliveryPolicy maximumRedeliveries="1" />
    <!-- mark this as handled -->
    <handled>
      <constant>true</constant>
    </handled>
    <!-- let our order service handle this exception, call the orderFailed method -->
    <bean ref="orderService" method="orderFailed" />
    <!-- and since this is a unit test we use mock for assertions -->
    <to uri="mock:error" />
  </onException>

  <route>
    <!-- the route -->
    <from uri="direct:start" />
    <!-- in the normal route then route to our order service and call handleOrder method -->
    <bean ref="orderService" method="handleOrder" />
    <!-- and since this is a unit test we use mock for assertions -->
    <to uri="mock:result" />
  </route>

</camelContext>

<!-- setup our error handler as the deal letter channel -->
<bean id="deadLetter" class="org.apache.camel.builder.DeadLetterChannelBuilder">
    <property name="deadLetterUri" value="mock:dead"/>
</bean>

<!-- the default error handler used in the 2nd route -->
<bean id="defaultErrorHandler" class="org.apache.camel.builder.DefaultErrorHandlerBuilder"/>

<!-- this is our POJO bean with our business logic defined as a plain spring bean -->
<bean id="orderService" class="org.apache.camel.spring.processor.onexception.OrderService"/>

<!-- this is the camel context where we define the routes -->
<camelContext xmlns="http://camel.apache.org/schema/spring">

    <route errorHandlerRef="deadLetter">
        <from uri="direct:start"/>
        <onException>
            <exception>org.apache.camel.spring.processor.onexception.OrderFailedException</exception>
            <redeliveryPolicy maximumRedeliveries="1"/>
            <handled>
                <constant>true</constant>
            </handled>
            <bean ref="orderService" method="orderFailed"/>
            <to uri="mock:error"/>
        </onException>
        <bean ref="orderService" method="handleOrder"/>
        <to uri="mock:result"/>
    </route>

    <!-- The exception clause specified in the first route will not be used in this route -->
    <route errorHandlerRef="defaultErrorHandler">
        <from uri="direct:start_with_no_handler"/>
        <bean ref="orderService" method="handleOrder"/>
        <to uri="mock:result"/>
    </route>

</camelContext>