Chapter 2. ActiveMQ
ActiveMQ Component
The ActiveMQ component allows messages to be sent to a JMS Queue or Topic; or messages to be consumed from a JMS Queue or Topic using Apache ActiveMQ.
This component is based on the JMS Component and uses Spring's JMS support for declarative transactions, using Spring's
JmsTemplate for sending and a MessageListenerContainer for consuming. All the options from the JMS component also apply for this component.
To use this component, make sure you have the
activemq.jar or activemq-core.jar on your classpath along with any Apache Camel dependencies such as camel-core.jar, camel-spring.jar and camel-jms.jar.
Transacted and caching
See section Transactions and Cache Levels below on JMS page if you are using transactions with JMS as it can impact performance.
URI format
activemq:[queue:|topic:]destinationName
Where destinationName is an ActiveMQ queue or topic name. By default, the destinationName is interpreted as a queue name. For example, to connect to the queue,
FOO.BAR, use:
activemq:FOO.BAR
You can include the optional
queue: prefix, if you prefer:
activemq:queue:FOO.BAR
To connect to a topic, you must include the
topic: prefix. For example, to connect to the topic, Stocks.Prices, use:
activemq:topic:Stocks.Prices
Options
See Options on the JMS component as all these options also apply for this component.
Configuring the Connection Factory
The following test case shows how to add an ActiveMQComponent to the CamelContext using the
activeMQComponent() method while specifying the brokerURL used to connect to ActiveMQ.
camelContext.addComponent("activemq", activeMQComponent("vm://localhost?broker.persistent=false"));
Configuring the Connection Factory using Spring XML
You can configure the ActiveMQ broker URL on the ActiveMQComponent as follows
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="
http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.0.xsd
http://camel.apache.org/schema/spring http://camel.apache.org/schema/spring/camel-spring.xsd">
<camelContext xmlns="http://camel.apache.org/schema/spring">
</camelContext>
<bean id="activemq" class="org.apache.activemq.camel.component.ActiveMQComponent">
<property name="brokerURL" value="tcp://somehost:61616"/>
</bean>
</beans>Using connection pooling
When sending to an ActiveMQ broker using Camel it's recommended to use a pooled connection factory to handle efficient pooling of JMS connections, sessions and producers. This is documented in the page ActiveMQ Spring Support.
You can grab Jencks AMQ pool with Maven:
<dependency>
<groupId>org.apache.activemq</groupId>
<artifactId>activemq-pool</artifactId>
<version>5.3.2</version>
</dependency>
And then setup the activemq component as follows:
<bean id="jmsConnectionFactory" class="org.apache.activemq.ActiveMQConnectionFactory">
<property name="brokerURL" value="tcp://localhost:61616" />
</bean>
<bean id="pooledConnectionFactory" class="org.apache.activemq.pool.PooledConnectionFactory" init-method="start" destroy-method="stop">
<property name="maxConnections" value="8" />
<property name="connectionFactory" ref="jmsConnectionFactory" />
</bean>
<bean id="jmsConfig" class="org.apache.camel.component.jms.JmsConfiguration">
<property name="connectionFactory" ref="pooledConnectionFactory"/>
<property name="concurrentConsumers" value="10"/>
</bean>
<bean id="activemq" class="org.apache.activemq.camel.component.ActiveMQComponent">
<property name="configuration" ref="jmsConfig"/>
</bean>
Note
Notice the init and destroy methods on the pooled connection factory. This is important to ensure the connection pool is properly started and shutdown.
The
PooledConnectionFactory will then create a connection pool with up to 8 connections in use at the same time. Each connection can be shared by many sessions. There is an option named maxActive you can use to configure the maximum number of sessions per connection; the default value is 500. From ActiveMQ 5.7 onwards the option has been renamed to better reflect its purpose, being named as maxActiveSessionPerConnection. Notice the concurrentConsumers is set to a higher value than maxConnections is. This is okay, as each consumer is using a session, and as a session can share the same connection, we are in the safe. In this example we can have 8 * 500 = 4000 active sessions at the same time.
Invoking MessageListener POJOs in a route
The ActiveMQ component also provides a helper Type Converter from a JMS MessageListener to a Processor. This means that the Bean component is capable of invoking any JMS MessageListener bean directly inside any route.
So for example you can create a MessageListener in JMS as follows:
public class MyListener implements MessageListener {
public void onMessage(Message jmsMessage) {
// ...
}
}
Then use it in your route as follows
from("file://foo/bar").
bean(MyListener.class);
That is, you can reuse any of the Apache Camel Components and easily integrate them into your JMS
MessageListener POJO\!
Using ActiveMQ Destination Options
Available as of ActiveMQ 5.6
You can configure the Destination Options in the endpoint uri, using the "destination." prefix. For example to mark a consumer as exclusive, and set its prefetch size to 50, you can do as follows:
<camelContext xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="file://src/test/data?noop=true"/>
<to uri="activemq:queue:foo"/>
</route>
<route>
<!-- use consumer.exclusive ActiveMQ destination option, notice we have to prefix with destination. -->
<from uri="activemq:foo?destination.consumer.exclusive=true&estination.consumer.prefetchSize=50"/>
<to uri="mock:results"/>
</route>
</camelContext>
Consuming Advisory Messages
ActiveMQ can generate Advisory messages which are put in topics that you can consume. Such messages can help you send alerts in case you detect slow consumers or to build statistics (number of messages/produced per day, etc.) The following Spring DSL example shows you how to read messages from a topic.
<route>
<from uri="activemq:topic:ActiveMQ.Advisory.Connection?mapJmsMessage=false" />
<convertBodyTo type="java.lang.String"/>
<transform>
<simple>${in.body} </simple>
</transform>
<to uri="file://data/activemq/?fileExist=Append&ileName=advisoryConnection-${date:now:yyyyMMdd}.txt" />
</route>
If you consume a message on a queue, you should see the following files under data/activemq folder :
advisoryConnection-20100312.txt advisoryProducer-20100312.txt
and containing string:
ActiveMQMessage {commandId = 0, responseRequired = false, messageId = ID:dell-charles-3258-1268399815140
-1:0:0:0:221, originalDestination = null, originalTransactionId = null, producerId = ID:dell-charles-
3258-1268399815140-1:0:0:0, destination = topic://ActiveMQ.Advisory.Connection, transactionId = null,
expiration = 0, timestamp = 0, arrival = 0, brokerInTime = 1268403383468, brokerOutTime = 1268403383468,
correlationId = null, replyTo = null, persistent = false, type = Advisory, priority = 0, groupID = null,
groupSequence = 0, targetConsumerId = null, compressed = false, userID = null, content = null,
marshalledProperties = org.apache.activemq.util.ByteSequence@17e2705, dataStructure = ConnectionInfo
{commandId = 1, responseRequired = true, connectionId = ID:dell-charles-3258-1268399815140-2:50,
clientId = ID:dell-charles-3258-1268399815140-14:0, userName = , password = *****,
brokerPath = null, brokerMasterConnector = false, manageable = true, clientMaster = true},
redeliveryCounter = 0, size = 0, properties = {originBrokerName=master, originBrokerId=ID:dell-charles-
3258-1268399815140-0:0, originBrokerURL=vm://master}, readOnlyProperties = true, readOnlyBody = true,
droppable = false}Getting Component JAR
You need this dependency:
activemq-camel
<dependency> <groupId>org.apache.activemq</groupId> <artifactId>activemq-camel</artifactId> <version>5.6.0</version> </dependency>
