Advanced configuration of CamelContext using Spring

When using Spring the CamelContext can be pre configured based on defined beans in spring XML.
This wiki page documentes these features. Most of these features requires Camel 2.0.

What can be configured

The following functions can be configured:

• Class resolvers
• Lifecycle factories
• Registry for lookup
• Debugger, Tracer, Delay and UuidGenerator
• Intercept
• Graceful Shutdown
• Stream caching
• Logging

Camel will configure these functions by doing a lookup in the Spring bean registry to find beans of the given type
When Camel finds and uses any of these it logs at INFO level.

The following list all requires at most 1 beans defined. If there are more than 1 bean of this type, then Camel will not use it.

And the following options have support for any number of beans defined.

Camel will log at INFO level if it pickup and uses a custom bean using org.apache.camel.spring.CamelContextFactoryBean as name.

Using container wide interceptors

Imagine that you have multiple CamelContext and you want to configure that they all use the same container wide interceptor. How do we do that? Well we can leverage the fact that Camel can auto detect and use custom interceptors. So what we simply do is to define our interceptor in the spring xml file. The sample below does this and also define 2 camel contexts. The sample is based on unit test.Error rendering macro 'code': Invalid value specified for parameter 'java.lang.NullPointerException'

<!-- here we define a spring bean that is our container wide interceptor
     its important to notice that the class ContainerWideInterceptor implements
     org.apache.camel.spi.InterceptStrategy that allows us to plugin our interceptors
     Camel will at startup automatic look for any beans in spring registry that is an
     instance of org.apache.camel.spi.InterceptStrategy and add it as interceptor
     to all its routes. Using this we are capable of defining container wide interceptors
     that gets used in all camel contests we define with spring -->
<bean id="myInterceptor" class="org.apache.camel.spring.interceptor.ContainerWideInterceptor"/>

<!-- here we have the 1st CamelContext -->
<camelContext id="camel1" xmlns="http://camel.apache.org/schema/spring">
    <route>
        <from uri="direct:one"/>
        <to uri="mock:result"/>
    </route>
</camelContext>

<!-- and there we have the 2nd CamelContext -->
<camelContext id="camel2" xmlns="http://camel.apache.org/schema/spring">
    <route>
        <from uri="direct:two"/>
        <to uri="log:two"/>
        <to uri="mock:result"/>
    </route>
</camelContext>

public class ContainerWideInterceptor implements InterceptStrategy {

    private static final Logger LOG = LoggerFactory.getLogger(ContainerWideInterceptor.class);
    private static int count;

    @Override
    public Processor wrapProcessorInInterceptors(final CamelContext context, final NamedNode definition,
                                                 final Processor target, final Processor nextTarget) throws Exception {

        // as this is based on an unit test we are a bit lazy and just create an inlined processor
        // where we implement our interception logic.
        return new Processor() {
            public void process(Exchange exchange) throws Exception {
                // we just count number of interceptions
                count++;
                LOG.info("I am the container wide interceptor. Intercepted total count: " + count);
                // its important that we delegate to the real target so we let target process the exchange
                target.process(exchange);
            }

            @Override
            public String toString() {
                return "ContainerWideInterceptor[" + target + "]";
            }
        };
    }

    public int getCount() {
        return count;
    }
}

INFO  CamelContextFactoryBean        - Using custom intercept strategy with id: myInterceptor and implementation:org.apache.camel.spring.interceptor.ContainerWideInterceptor@b84c44

Notice: If we have more than 1 container wide interceptor, we can just define them as spring bean. Camel will find and use them.

See Also

• Spring
• Spring JMS Tutorial
• Creating a new Spring based Camel Route
• Spring example
• Xml Reference