Walk through an Example Code

This mini-guide takes you through the source code of a simple example].

Camel can be configured either by using Spring or directly in Java - which this example does.

We start with creating a CamelContext - which is a container for Components, Routes etc:

CamelContext context = new DefaultCamelContext();

There is more than one way of adding a Component to the CamelContext. You can add components implicitly - when we set up the routing - as we do here for the FileComponent:

context.addRoutes(new RouteBuilder() {

    public void configure() {
        from("test-jms:queue:test.queue").to("file://test");
        // set up a listener on the file component
        from("file://test").process(new Processor() {

            public void process(Exchange e) {
                System.out.println("Received exchange: " + e.getIn());
            }
        });
    }
});

or explicitly - as we do here when we add the JMS Component:

ConnectionFactory connectionFactory = new ActiveMQConnectionFactory("vm://localhost?broker.persistent=false");
// note we can explicity name the component
context.addComponent("test-jms", JmsComponent.jmsComponentAutoAcknowledge(connectionFactory));

The above works with any JMS provider. If we know we are using ActiveMQ we can use an even simpler form using the activeMQComponent() method while specifying the brokerURL used to connect to ActiveMQ

camelContext.addComponent("activemq", activeMQComponent("vm://localhost?broker.persistent=false"));

In normal use, an external system would be firing messages or events into directly into Camel through one if its Components but we are going to use the CamelTemplate which is a really nice an easy way for testing your configuration:

CamelTemplate template = new CamelTemplate(context);

Next you must start the camel context. If you are using Spring to configure the camel context this is automatically done for you; though if you are using a pure Java approach then you just need to call the start() method

camelContext.start();

This will start all of the configured routing rules.

So after starting the CamelContext, we can fire some objects into camel:

for (int i = 0; i < 10; i++) {
    template.sendBody("test-jms:queue:test.queue", "Test Message: " + i);
}

What happens ?

From the CamelClient - we send objects (in this case text) into the CamelContext to the Component test-jms:queue:test.queue. These text objects will be converted automatically into JMS Messages and posted to a JMS Queue named test.queue. When we set up the Route, we configured the FileComponent to listen of the test.queue.

The File FileComponent will take messages of the Queue, and save them to a directory named test. Every message will be saved in a file that corresponds to its destination and message id.

Finally, we configured our own listener in the Route - to take notifications from the FileComponent and print them out as text.

Thats it!

Graphic Design By Hiram