The Java code for this recipe is located in the org.camelcookbook.error.logging package. The Spring XML files are located under src/main/resources/META-INF/spring and prefixed with logging.

In the XML DSL, define an errorHandler element within the camelContext element, and reference the error handler's id in the errorHandlerRef attribute of the camelContext element. The type attribute of the errorHandler element must be set to "LoggingErrorHandler". You can optionally set the level (defaults to ERROR), and logName (defaults to Logger) attributes. This will set up the base error handler for all routes defined within this Camel context. Refer to the following code for the same:

<camelContext errorHandlerRef="myErrorHandler"
              xmlns="http://camel.apache.org/schema/spring">
  <errorHandler id="myErrorHandler"
                type="LoggingErrorHandler"
                level="ERROR"
                logName="MyLoggingErrorHandler"/>

  <route>
    <from uri="direct:start"/>
    <!-- ... -->
  </route>
</camelContext>

In the Java DSL, within the RouteBuilder.configure() method, define an errorHandler instance that references a LoggingErrorHandler instance, configured using the DSL's fluent API. You can set the level attribute (defaults to ERROR) and logName (defaults to Logger). This will configure the base error handler for all routes defined within this RouteBuilder implementation.

public class LoggingRouteBuilder extends RouteBuilder {
  @Override
  public void configure() throws Exception {
    errorHandler(loggingErrorHandler()
        .logName("MyLoggingErrorHandler")
        .level(LoggingLevel.ERROR)
    );

    from("direct:start")
    //...
  }
}

Camel uses the SLF4J logging library under the covers to configure logging. The SLF4J library allows Camel to work with many different logging implementations. This allows you to configure runtime properties according to the implementation being used, for example, within the log4j.properties file, if Log4j is used.

Setting the logName attribute is equivalent to calling SLF4J's LoggerFactory.getLogger(logName). This allows you to quickly find and automatically filter log messages by using this String, which helps you determine what is happening within your integration.

For example, here is a log entry based on the preceding sample code. Notice how our logName setting is accessible within the log:

2013-05-28 07:21:36,913 [main           ] ERROR MyLoggingErrorHandler          - Failed delivery for (MessageId: ID-grelber-local-56780-1369740096617-0-3 on ExchangeId: ID-grelber-local-56780-1369740096617-0-4). Exhausted after delivery attempt: 1 caught: org.camelcookbook.error.logging.FlakyException: FlakyProcessor has gone Flaky

It is also possible to set route-specific error handlers.

In the XML DSL, you can set the errorHandlerRef attribute of the route element using the following code:

<camelContext xmlns="http://camel.apache.org/schema/spring">
  <errorHandler id="myRouteSpecificLogging"
                type="LoggingErrorHandler"
                level="ERROR"
                logName="MyRouteLogging"/>

  <route errorHandlerRef="myRouteSpecificLogging">
    <from uri="direct:start"/>
    <!-- ... -->
  </route>
</camelContext>

In the Java DSL, you specify the route-specific error handler after the from part of the route definition:

from("direct:start")
    .errorHandler(loggingErrorHandler()
        .logName("MyRouteLogging")
        .level(LoggingLevel.ERROR)
    )
  .bean(FlakyProcessor.class)
  .to("mock:result");