4.2. Message Channel

A message channel is a logical channel in a messaging system. That is, sending messages to different message channels provides an elementary way of sorting messages into different message types. Message queues and message topics are examples of message channels. You should remember that a logical channel is not the same as a physical channel. There can be several different ways of physically realizing a logical channel.

In Apache Camel, a message channel is represented by an endpoint URI of a message-oriented component as shown in Figure 4.2, “Message Channel Pattern”.

The following message-oriented components in Apache Camel support the notion of a message channel:

In ActiveMQ, message channels are represented by queues or topics. The endpoint URI for a specific queue, QueueName, has the following format:

activemq:QueueName

activemq:QueueName

The endpoint URI for a specific topic, TopicName, has the following format:

activemq:topic:TopicName

activemq:topic:TopicName

For example, to send messages to the queue, Foo.Bar, use the following endpoint URI:

activemq:Foo.Bar

activemq:Foo.Bar

See chapter "ActiveMQ" in "EIP Component Reference" for more details and instructions on setting up the ActiveMQ component.

The Java Messaging Service (JMS) is a generic wrapper layer that is used to access many different kinds of message systems (for example, you can use it to wrap ActiveMQ, MQSeries, Tibco, BEA, Sonic, and others). In JMS, message channels are represented by queues, or topics. The endpoint URI for a specific queue, QueueName, has the following format:

jms:QueueName

jms:QueueName

The endpoint URI for a specific topic, TopicName, has the following format:

jms:topic:TopicName

jms:topic:TopicName

See chapter "JMS" in "EIP Component Reference" for more details and instructions on setting up the JMS component.

In AMQP, message channels are represented by queues, or topics. The endpoint URI for a specific queue, QueueName, has the following format:

amqp:QueueName

amqp:QueueName

The endpoint URI for a specific topic, TopicName, has the following format:

amqp:topic:TopicName

amqp:topic:TopicName

See chapter "AMQP" in "EIP Component Reference" for more details and instructions on setting up the AMQP component.