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6.2. Publish-Subscribe Channel


A publish-subscribe channel, shown in Figure 6.2, “Publish Subscribe Channel Pattern”, is a message channel that enables multiple subscribers to consume any given message. This is in contrast with a point-to-point channel. Publish-subscribe channels are frequently used as a means of broadcasting events or notifications to multiple subscribers.

Figure 6.2. Publish Subscribe Channel Pattern

Publish subscribe channel pattern

Components that support publish-subscribe channel

The following Apache Camel components support the publish-subscribe channel pattern:
  • JMS
  • SEDA for working with SEDA in the same CamelContext which can work in pub-sub, but allowing multiple consumers.
  • VM as SEDA, but for use within the same JVM.


In JMS, a publish-subscribe channel is represented by a topic. For example, you can specify the endpoint URI for a JMS topic called StockQuotes as follows:


In ActiveMQ, a publish-subscribe channel is represented by a topic. For example, you can specify the endpoint URI for an ActiveMQ topic called StockQuotes, as follows:


The XMPP (Jabber) component supports the publish-subscribe channel pattern when it is used in the group communication mode. See chapter "XMPP" in "Apache Camel Component Reference" for more details.

Static subscription lists

If you prefer, you can also implement publish-subscribe logic within the Apache Camel application itself. A simple approach is to define a static subscription list, where the target endpoints are all explicitly listed at the end of the route. However, this approach is not as flexible as a JMS or ActiveMQ topic.

Java DSL example

The following Java DSL example shows how to simulate a publish-subscribe channel with a single publisher, seda:a, and three subscribers, seda:b, seda:c, and seda:d:
from("seda:a").to("seda:b", "seda:c", "seda:d");
This only works for the InOnly message exchange pattern.

XML configuration example

The following example shows how to configure the same route in XML:
<camelContext id="buildStaticRecipientList" xmlns="">
    <from uri="seda:a"/>
    <to uri="seda:b"/>
    <to uri="seda:c"/>
    <to uri="seda:d"/>