Define your desired routing logic as described in either the Using Camel in a Java application recipe, or the Embedding Camel in a Spring application recipe.

The Java code for this recipe is located in the org.camelcookbook.structuringroutes.routecontrol package.

Set the startupOrder property associated with the route.

In the XML DSL, add a startupOrder attribute to the route element:

<route startupOrder="20">
  <from uri="jms:queue:orders"/>
  <to uri="direct:processOrder"/>
</route>

<route startupOrder="10">
  <from uri="direct:processOrder"/>
  <process ref="orderProcessor"/>
</route>

In the Java DSL, call the startupOrder(..) method after the from statement:

from("jms:queue:orders").startupOrder(20)
  .to("direct:processOrder");

from("direct:processOrder").startupOrder(10)
  .process(new OrderProcessor());

Routes are started in ascending startupOrder. In the preceding examples, the direct: route will be started before the main entry point to the integration, which consumes from JMS.

You can assign any integer greater than 0 and less than 1,000 to the startupOrder. You cannot assign the same value more than once in a Camel context, otherwise it will refuse to start up. Camel will automatically assign values greater than 1,000 to any routes that do not specifically have one defined.

When you shut down the application, Camel will turn off the routes in the reverse order to that in which it started them. Routes are turned off in descending order.

When a route shuts down, the endpoint consumer is first turned off, and any messages that are flowing through the route ("in-flight") are allowed to complete before the route itself is shut down. Any messages that remain in-flight will be discarded after a timeout of 300 seconds. The timeout is configurable on the Camel context's associated ShutdownStrategy.

Routes can be started and shut down programmatically through the CamelContext startRoute() and stopRoute() methods. Since the context is accessible through an Exchange it is possible to perform custom route control logic. Take, as an example, the following class that stops a route whose name is specified by the body of the exchange:

public class RouteStoppingProcessor implements Processor {
  @Override
  public void process(Exchange exchange) throws Exception {
    final String routeName = 
        exchange.getIn().getBody(String.class);
    final CamelContext context = exchange.getContext();
    new Thread(new Runnable() {
      @Override
      public void run() {
        try {
          context.stopRoute(routeName);
        } catch (Exception e) {
          throw new RuntimeException(e);
        }
      }
    }).start();
  }
}

Routes can also be stopped and started through the use of a Control Bus endpoint:

from("direct:in").id("mainRoute")
  .log("Stopping route")
  .to("controlbus:route?routeId=mainRoute&action=stop&async=true")
  .log("Signalled to stop route")
  .to("mock:out");

Manual route control does not take into account the startupOrder, so you must take care when performing it that any routes that you start up or shut down are controlled in an orderly manner.

Routes can be turned off at startup by setting the autoStartup attribute to false.

In the XML DSL, add an autoStartup attribute to the route element:

<route autoStartup="false">
  <from uri="jms:queue:orders"/>
  <!-- ... -->
</route>

In the Java DSL, call the autoStartup(..) method after the from statement:

from("jms:queue:orders").autoStartup(false)...

You would use this feature if you want to control route availability manually, or through a route policy.

A RoutePolicy is an interface that you can build upon to determine whether routes should be running or not. Camel provides route policies out of the box for throttling routes (ThrottlingInflightRoutePolicy), defining uptime through a timer (SimpleScheduledRoutePolicy), and cron expressions (CronScheduledRoutePolicy).