When you need to route messages based on the content of the message, and/or based on the headers or properties associated with the message, using Camel's Content Based Router EIP is a great way to do that.

Content Based Routing and Filtering are very similar. A Content Based Router has multiple predicates, and the contained steps are performed on the first predicate that the message matches, or the optional otherwise statement if none matches (similar to an if () {..} else if () {..} else {..} statement in Java).

Camel's Filter EIP tests against a single predicate, executing the contained processing steps only if the message matches that predicate. The equivalent of a Filter in Java would be a single if statement.

In this recipe, we will see how to use a Content Based Router to route a message to one of the several destinations based on the content (the body) of the message.

When you need to perform a sequence of steps only when a message matches a certain condition (Predicate), then a Filter is a good option.

Content Based Routing and Filtering are very similar. Filtering processes a message only if it matches the single predicate provided (much like a single if statement).

A Content Based Router routes a message based on the first of the multiple predicates, or the optional otherwise statement if none of the provided predicates matched (similar to an if () {..} else if () {..} else {..} statement in Java).

This recipe will show you how to perform message processing steps only on those messages that match a specified predicate.

When you want to process the current message in the background (concurrently) to the main route, without requiring a response, the Wire Tap EIP can help. A typical use case for this is logging the message to a backend system. The main thread of execution will continue to process the message through the current route as usual, while Wire Tap allows additional messaging processing to occur outside of the main route.

This recipe will show you how to send a copy of the message to a different endpoint.

<route>
  <from uri="direct:start"/>
  <wireTap uri="mock...

When you want to route the same message to a number of endpoints and have them process the message in different ways, the Multicast EIP is a good choice.

This recipe will show you the default, sequential way to use Camel's Multicast EIP. Chapter 6, Parallel Processing, contains a recipe for using Multicast with concurrency (threads).

<route>
  <from uri="direct:start"/>
  <multicast>
    <to uri="mock:first"/>
    <to uri="mock:second"/>
    <to uri="mock:third"/>
  </multicast>
</route...

When you want to dynamically (at runtime) decide a list of endpoints that an individual message should be sent to, use the Recipient List EIP. This EIP is made up of two phases: deciding where to route the message, and subsequently invoking those route steps. It can be thought of as a dynamic Multicast, and behaves in much the same way.

This recipe will show you how to route a message to a number of dynamically specified endpoints.

<route>
  <from uri="direct:start"/>
  <setHeader...

When you need to limit the number of messages flowing through a route during a specified time period, the Throttler EIP can help. For example, if you have a downstream system that can only handle 10 requests per second, using a Throttler EIP within your route can ensure that you do not exceed that rate.

This recipe will show you how to restrict the number of messages routed to a set of endpoints during a specified time period.

When processing a message in a Request-Response (InOut) route, you sometimes need to send the message to an endpoint, but do not want to receive a response. This recipe shows you how to invoke such an endpoint using the InOnly MEP.

The MEP used can radically alter the behavior of an endpoint. For example, if you invoke a JMS endpoint within a request-response (InOut) route, it will send a message to a queue and set up a listener on a temporary destination waiting for a response; this is known as request-response over messaging. If the consumer of the message on the other side of the queue has not been written to send a response message, your route will wait indefinitely (or as long as the configurable timeout of the component).

This recipe shows how you can alter the MEP temporarily in order to send messages one way in a request-response route.