Chapter 5. Messaging Channels

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.

The following Apache Camel components support the point-to-point channel pattern:

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

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

jms:Foo.Bar

See chapter "JMS" in "EIP Component Reference" for more details.

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

activemq:queue:Foo.Bar

See chapter "ActiveMQ" in "EIP Component Reference" for more details.

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

seda:SedaQueue

The Java Persistence API (JPA) component is an EJB 3 persistence standard that is used to write entity beans out to a database. See chapter "JPA" in "EIP Component Reference" for more details.

The XMPP (Jabber) component supports the point-to-point channel pattern when it is used in the person-to-person mode of communication. See chapter "XMPP" in "EIP Component Reference" for more details.