Chapter 5. Messaging Channels
Abstract
Messaging channels provide the plumbing for a messaging application. This chapter describes the different kinds of messaging channels available in a messaging system, and the roles that they play.
5.1. Point-to-Point Channel
Overview
A point-to-point channel, shown in Figure 5.1, “Point to Point Channel Pattern” is a message channel that guarantees that only one receiver consumes any given message. This is in contrast with a publish-subscribe channel, which allows multiple receivers to consume the same message. In particular, with a point-to-point channel, it is possible for multiple receivers to subscribe to the same channel. If more than one receiver competes to consume a message, it is up to the message channel to ensure that only one receiver actually consumes the message.
Figure 5.1. Point to Point Channel Pattern
![Point to point channel pattern](https://access.redhat.com/webassets/avalon/d/Red_Hat_JBoss_Fuse-6.1-Apache_Camel_Development_Guide-en-US/images/e0beee5d06fa41eed6d4f756969b86e4/point_to_point.gif)
Components that support point-to-point channel
The following Apache Camel components support the point-to-point channel pattern:
JMS
In JMS, a point-to-point channel is represented by a queue. For example, you can specify the endpoint URI for a JMS queue called
Foo.Bar
as follows:
jms:queue:Foo.Bar
The qualifier,
queue:
, is optional, because the JMS component creates a queue endpoint by default. Therefore, you can also specify the following equivalent endpoint URI:
jms:Foo.Bar
ActiveMQ
In ActiveMQ, a point-to-point channel is represented by a queue. For example, you can specify the endpoint URI for an ActiveMQ queue called
Foo.Bar
as follows:
activemq:queue:Foo.Bar
SEDA
The Apache Camel Staged Event-Driven Architecture (SEDA) component is implemented using a blocking queue. Use the SEDA component if you want to create a lightweight point-to-point channel that is internal to the Apache Camel application. For example, you can specify an endpoint URI for a SEDA queue called
SedaQueue
as follows:
seda:SedaQueue