757 lines
24 KiB
Markdown
757 lines
24 KiB
Markdown
Examples
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========
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The ActiveMQ distribution comes with over 70 run out-of-the-box examples
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demonstrating many of the features.
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The examples are available in the distribution, in the `examples`
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directory. Examples are split into JMS and core examples. JMS examples
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show how a particular feature can be used by a normal JMS client. Core
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examples show how the equivalent feature can be used by a core messaging
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client.
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A set of Java EE examples are also provided which need WildFly installed
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to be able to run.
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JMS Examples
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============
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To run a JMS example, simply `cd` into the appropriate example directory
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and type `mvn verify` (For details please read the readme.html in each
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example directory).
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Here's a listing of the examples with a brief description.
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JMS AeroGear
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------------
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This example shows how you can send a message to a mobile device by
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leveraging AeroGears push technology which provides support for
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different push notification technologies like Google Cloud Messaging,
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Apple's APNs or Mozilla's SimplePush.
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Applet
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------
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This example shows you how to send and receive JMS messages from an
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Applet.
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Application-Layer Failover
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--------------------------
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ActiveMQ also supports Application-Layer failover, useful in the case
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that replication is not enabled on the server side.
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With Application-Layer failover, it's up to the application to register
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a JMS `ExceptionListener` with ActiveMQ which will be called by ActiveMQ
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in the event that connection failure is detected.
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The code in the `ExceptionListener` then recreates the JMS connection,
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session, etc on another node and the application can continue.
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Application-layer failover is an alternative approach to High
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Availability (HA). Application-layer failover differs from automatic
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failover in that some client side coding is required in order to
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implement this. Also, with Application-layer failover, since the old
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session object dies and a new one is created, any uncommitted work in
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the old session will be lost, and any unacknowledged messages might be
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redelivered.
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Core Bridge Example
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-------------------
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The `bridge` example demonstrates a core bridge deployed on one server,
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which consumes messages from a local queue and forwards them to an
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address on a second server.
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Core bridges are used to create message flows between any two ActiveMQ
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servers which are remotely separated. Core bridges are resilient and
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will cope with temporary connection failure allowing them to be an ideal
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choice for forwarding over unreliable connections, e.g. a WAN.
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Browser
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-------
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The `browser` example shows you how to use a JMS `QueueBrowser` with
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ActiveMQ.
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Queues are a standard part of JMS, please consult the JMS 1.1
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specification for full details.
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A `QueueBrowser` is used to look at messages on the queue without
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removing them. It can scan the entire content of a queue or only
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messages matching a message selector.
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Client Kickoff
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--------------
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The `client-kickoff` example shows how to terminate client connections
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given an IP address using the JMX management API.
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Client side failover listener
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-----------------------------
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The `client-side-failoverlistener` example shows how to register a
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listener to monitor failover events
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Client-Side Load-Balancing
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--------------------------
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The `client-side-load-balancing` example demonstrates how sessions
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created from a single JMS `Connection` can be created to different nodes
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of the cluster. In other words it demonstrates how ActiveMQ does
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client-side load-balancing of sessions across the cluster.
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Clustered Durable Subscription
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------------------------------
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This example demonstrates a clustered JMS durable subscription
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Clustered Grouping
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------------------
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This is similar to the message grouping example except that it
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demonstrates it working over a cluster. Messages sent to different nodes
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with the same group id will be sent to the same node and the same
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consumer.
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Clustered Queue
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---------------
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The `clustered-queue` example demonstrates a JMS queue deployed on two
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different nodes. The two nodes are configured to form a cluster. We then
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create a consumer for the queue on each node, and we create a producer
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on only one of the nodes. We then send some messages via the producer,
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and we verify that both consumers receive the sent messages in a
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round-robin fashion.
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Clustering with JGroups
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-----------------------
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The `clustered-jgroups` example demonstrates how to form a two node
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cluster using JGroups as its underlying topology discovery technique,
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rather than the default UDP broadcasting. We then create a consumer for
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the queue on each node, and we create a producer on only one of the
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nodes. We then send some messages via the producer, and we verify that
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both consumers receive the sent messages in a round-robin fashion.
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Clustered Standalone
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--------------------
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The `clustered-standalone` example demonstrates how to configure and
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starts 3 cluster nodes on the same machine to form a cluster. A
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subscriber for a JMS topic is created on each node, and we create a
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producer on only one of the nodes. We then send some messages via the
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producer, and we verify that the 3 subscribers receive all the sent
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messages.
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Clustered Static Discovery
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--------------------------
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This example demonstrates how to configure a cluster using a list of
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connectors rather than UDP for discovery
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Clustered Static Cluster One Way
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--------------------------------
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This example demonstrates how to set up a cluster where cluster
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connections are one way, i.e. server A -\> Server B -\> Server C
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Clustered Topic
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---------------
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The `clustered-topic` example demonstrates a JMS topic deployed on two
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different nodes. The two nodes are configured to form a cluster. We then
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create a subscriber on the topic on each node, and we create a producer
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on only one of the nodes. We then send some messages via the producer,
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and we verify that both subscribers receive all the sent messages.
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Message Consumer Rate Limiting
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------------------------------
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With ActiveMQ you can specify a maximum consume rate at which a JMS
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MessageConsumer will consume messages. This can be specified when
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creating or deploying the connection factory.
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If this value is specified then ActiveMQ will ensure that messages are
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never consumed at a rate higher than the specified rate. This is a form
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of consumer throttling.
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Dead Letter
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-----------
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The `dead-letter` example shows you how to define and deal with dead
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letter messages. Messages can be delivered unsuccessfully (e.g. if the
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transacted session used to consume them is rolled back).
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Such a message goes back to the JMS destination ready to be redelivered.
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However, this means it is possible for a message to be delivered again
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and again without any success and remain in the destination, clogging
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the system.
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To prevent this, messaging systems define dead letter messages: after a
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specified unsuccessful delivery attempts, the message is removed from
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the destination and put instead in a dead letter destination where they
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can be consumed for further investigation.
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Delayed Redelivery
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------------------
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The `delayed-redelivery` example demonstrates how ActiveMQ can be
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configured to provide a delayed redelivery in the case a message needs
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to be redelivered.
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Delaying redelivery can often be useful in the case that clients
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regularly fail or roll-back. Without a delayed redelivery, the system
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can get into a "thrashing" state, with delivery being attempted, the
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client rolling back, and delivery being re-attempted in quick
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succession, using up valuable CPU and network resources.
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Divert
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------
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ActiveMQ diverts allow messages to be transparently "diverted" or copied
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from one address to another with just some simple configuration defined
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on the server side.
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Durable Subscription
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--------------------
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The `durable-subscription` example shows you how to use a durable
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subscription with ActiveMQ. Durable subscriptions are a standard part of
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JMS, please consult the JMS 1.1 specification for full details.
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Unlike non-durable subscriptions, the key function of durable
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subscriptions is that the messages contained in them persist longer than
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the lifetime of the subscriber - i.e. they will accumulate messages sent
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to the topic even if there is no active subscriber on them. They will
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also survive server restarts or crashes. Note that for the messages to
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be persisted, the messages sent to them must be marked as durable
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messages.
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Embedded
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--------
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The `embedded` example shows how to embed JMS within your own code using
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POJO instantiation and no config files.
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Embedded Simple
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---------------
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The `embedded` example shows how to embed JMS within your own code using
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regular ActiveMQ XML files.
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Message Expiration
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------------------
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The `expiry` example shows you how to define and deal with message
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expiration. Messages can be retained in the messaging system for a
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limited period of time before being removed. JMS specification states
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that clients should not receive messages that have been expired (but it
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does not guarantee this will not happen).
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ActiveMQ can assign an expiry address to a given queue so that when
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messages are expired, they are removed from the queue and sent to the
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expiry address. These "expired" messages can later be consumed from the
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expiry address for further inspection.
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ActiveMQ Resource Adapter example
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---------------------------------
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This examples shows how to build the activemq resource adapters a rar
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for deployment in other Application Server's
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HTTP Transport
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--------------
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The `http-transport` example shows you how to configure ActiveMQ to use
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the HTTP protocol as its transport layer.
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Instantiate JMS Objects Directly
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--------------------------------
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Usually, JMS Objects such as `ConnectionFactory`, `Queue` and `Topic`
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instances are looked up from JNDI before being used by the client code.
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This objects are called "administered objects" in JMS terminology.
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However, in some cases a JNDI server may not be available or desired. To
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come to the rescue ActiveMQ also supports the direct instantiation of
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these administered objects on the client side so you don't have to use
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JNDI for JMS.
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Interceptor
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-----------
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ActiveMQ allows an application to use an interceptor to hook into the
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messaging system. Interceptors allow you to handle various message
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events in ActiveMQ.
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JAAS
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----
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The `jaas` example shows you how to configure ActiveMQ to use JAAS for
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security. ActiveMQ can leverage JAAS to delegate user authentication and
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authorization to existing security infrastructure.
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JMS Auto Closable
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-----------------
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The `jms-auto-closeable` example shows how JMS resources, such as
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connections, sessions and consumers, in JMS 2 can be automatically
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closed on error.
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JMS Completion Listener
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-----------------------
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The `jms-completion-listener` example shows how to send a message
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asynchronously to ActiveMQ and use a CompletionListener to be notified
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of the Broker receiving it.
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JMS Bridge
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----------
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The `jms-brige` example shows how to setup a bridge between two
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standalone ActiveMQ servers.
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JMS Context
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-----------
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The `jms-context` example shows how to send and receive a message to a
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JMS Queue using ActiveMQ by using a JMS Context.
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A JMSContext is part of JMS 2.0 and combines the JMS Connection and
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Session Objects into a simple Interface.
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JMS Shared Consumer
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-------------------
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The `jms-shared-consumer` example shows you how can use shared consumers
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to share a subscription on a topic. In JMS 1.1 this was not allowed and
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so caused a scalability issue. In JMS 2 this restriction has been lifted
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so you can share the load across different threads and connections.
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JMX Management
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--------------
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The `jmx` example shows how to manage ActiveMQ using JMX.
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Large Message
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-------------
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The `large-message` example shows you how to send and receive very large
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messages with ActiveMQ. ActiveMQ supports the sending and receiving of
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huge messages, much larger than can fit in available RAM on the client
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or server. Effectively the only limit to message size is the amount of
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disk space you have on the server.
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Large messages are persisted on the server so they can survive a server
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restart. In other words ActiveMQ doesn't just do a simple socket stream
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from the sender to the consumer.
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Last-Value Queue
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----------------
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The `last-value-queue` example shows you how to define and deal with
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last-value queues. Last-value queues are special queues which discard
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any messages when a newer message with the same value for a well-defined
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last-value property is put in the queue. In other words, a last-value
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queue only retains the last value.
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A typical example for last-value queue is for stock prices, where you
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are only interested by the latest price for a particular stock.
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Management
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----------
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The `management` example shows how to manage ActiveMQ using JMS Messages
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to invoke management operations on the server.
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Management Notification
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-----------------------
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The `management-notification` example shows how to receive management
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notifications from ActiveMQ using JMS messages. ActiveMQ servers emit
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management notifications when events of interest occur (consumers are
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created or closed, addresses are created or deleted, security
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authentication fails, etc.).
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Message Counter
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---------------
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The `message-counters` example shows you how to use message counters to
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obtain message information for a JMS queue.
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Message Group
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-------------
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The `message-group` example shows you how to configure and use message
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groups with ActiveMQ. Message groups allow you to pin messages so they
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are only consumed by a single consumer. Message groups are sets of
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messages that has the following characteristics:
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- Messages in a message group share the same group id, i.e. they have
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same JMSXGroupID string property values
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- The consumer that receives the first message of a group will receive
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all the messages that belongs to the group
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Message Group
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-------------
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The `message-group2` example shows you how to configure and use message
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groups with ActiveMQ via a connection factory.
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Message Priority
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----------------
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Message Priority can be used to influence the delivery order for
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messages.
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It can be retrieved by the message's standard header field 'JMSPriority'
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as defined in JMS specification version 1.1.
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The value is of type integer, ranging from 0 (the lowest) to 9 (the
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highest). When messages are being delivered, their priorities will
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effect their order of delivery. Messages of higher priorities will
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likely be delivered before those of lower priorities.
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Messages of equal priorities are delivered in the natural order of their
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arrival at their destinations. Please consult the JMS 1.1 specification
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for full details.
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Multiple Failover
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-----------------
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This example demonstrates how to set up a live server with multiple
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backups
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Multiple Failover Failback
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--------------------------
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This example demonstrates how to set up a live server with multiple
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backups but forcing failover back to the original live server
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No Consumer Buffering
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---------------------
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By default, ActiveMQ consumers buffer messages from the server in a
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client side buffer before you actually receive them on the client side.
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This improves performance since otherwise every time you called
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receive() or had processed the last message in a
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`MessageListener onMessage()` method, the ActiveMQ client would have to
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go the server to request the next message, which would then get sent to
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the client side, if one was available.
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This would involve a network round trip for every message and reduce
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performance. Therefore, by default, ActiveMQ pre-fetches messages into a
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buffer on each consumer.
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In some case buffering is not desirable, and ActiveMQ allows it to be
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switched off. This example demonstrates that.
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Non-Transaction Failover With Server Data Replication
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-----------------------------------------------------
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The `non-transaction-failover` example demonstrates two servers coupled
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as a live-backup pair for high availability (HA), and a client using a
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*non-transacted* JMS session failing over from live to backup when the
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live server is crashed.
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ActiveMQ implements failover of client connections between live and
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backup servers. This is implemented by the replication of state between
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live and backup nodes. When replication is configured and a live node
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crashes, the client connections can carry and continue to send and
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consume messages. When non-transacted sessions are used, once and only
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once message delivery is not guaranteed and it is possible that some
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messages will be lost or delivered twice.
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OpenWire
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--------
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The `Openwire` example shows how to configure a ActiveMQ server to
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communicate with an ActiveMQ JMS client that uses open-wire protocol.
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Paging
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------
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The `paging` example shows how ActiveMQ can support huge queues even
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when the server is running in limited RAM. It does this by transparently
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*paging* messages to disk, and *depaging* them when they are required.
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Pre-Acknowledge
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---------------
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Standard JMS supports three acknowledgement modes:`
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AUTO_ACKNOWLEDGE`, `CLIENT_ACKNOWLEDGE`, and
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`DUPS_OK_ACKNOWLEDGE`. For a full description on these modes please
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consult the JMS specification, or any JMS tutorial.
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All of these standard modes involve sending acknowledgements from the
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client to the server. However in some cases, you really don't mind
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losing messages in event of failure, so it would make sense to
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acknowledge the message on the server before delivering it to the
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client. This example demonstrates how ActiveMQ allows this with an extra
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acknowledgement mode.
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Message Producer Rate Limiting
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------------------------------
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The `producer-rte-limit` example demonstrates how, with ActiveMQ, you
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can specify a maximum send rate at which a JMS message producer will
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send messages.
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Proton Qpid
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-----------
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ActiveMQ can be configured to accept requests from any AMQP client that
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supports the 1.0 version of the protocol. This `proton-j` example shows
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a simply qpid java 1.0 client example.
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Proton Ruby
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-----------
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ActiveMQ can be configured to accept requests from any AMQP client that
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supports the 1.0 version of the protocol. This example shows a simply
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proton ruby client that sends and receives messages
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Queue
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-----
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A simple example demonstrating a JMS queue.
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Message Redistribution
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----------------------
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The `queue-message-redistribution` example demonstrates message
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redistribution between queues with the same name deployed in different
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nodes of a cluster.
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Queue Requestor
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---------------
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A simple example demonstrating a JMS queue requestor.
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Queue with Message Selector
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---------------------------
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The `queue-selector` example shows you how to selectively consume
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messages using message selectors with queue consumers.
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Reattach Node example
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---------------------
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The `Reattach Node` example shows how a client can try to reconnect to
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the same server instead of failing the connection immediately and
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notifying any user ExceptionListener objects. ActiveMQ can be configured
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to automatically retry the connection, and reattach to the server when
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it becomes available again across the network.
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Replicated Failback example
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---------------------------
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An example showing how failback works when using replication, In this
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example a live server will replicate all its Journal to a backup server
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as it updates it. When the live server crashes the backup takes over
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from the live server and the client reconnects and carries on from where
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it left off.
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Replicated Failback static example
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----------------------------------
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An example showing how failback works when using replication, but this
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time with static connectors
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Replicated multiple failover example
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------------------------------------
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An example showing how to configure multiple backups when using
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replication
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Replicated Failover transaction example
|
|
---------------------------------------
|
|
|
|
An example showing how failover works with a transaction when using
|
|
replication
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|
|
|
Request-Reply example
|
|
---------------------
|
|
|
|
A simple example showing the JMS request-response pattern.
|
|
|
|
Rest example
|
|
------------
|
|
|
|
An example showing how to use the ActiveMQ Rest API
|
|
|
|
Scheduled Message
|
|
-----------------
|
|
|
|
The `scheduled-message` example shows you how to send a scheduled
|
|
message to a JMS Queue with ActiveMQ. Scheduled messages won't get
|
|
delivered until a specified time in the future.
|
|
|
|
Security
|
|
--------
|
|
|
|
The `security` example shows you how configure and use role based queue
|
|
security with ActiveMQ.
|
|
|
|
Send Acknowledgements
|
|
---------------------
|
|
|
|
The `send-acknowledgements` example shows you how to use ActiveMQ's
|
|
advanced *asynchronous send acknowledgements* feature to obtain
|
|
acknowledgement from the server that sends have been received and
|
|
processed in a separate stream to the sent messages.
|
|
|
|
Spring Integration
|
|
------------------
|
|
|
|
This example shows how to use embedded JMS using ActiveMQ's Spring
|
|
integration.
|
|
|
|
SSL Transport
|
|
-------------
|
|
|
|
The `ssl-enabled` shows you how to configure SSL with ActiveMQ to send
|
|
and receive message.
|
|
|
|
Static Message Selector
|
|
-----------------------
|
|
|
|
The `static-selector` example shows you how to configure a ActiveMQ core
|
|
queue with static message selectors (filters).
|
|
|
|
Static Message Selector Using JMS
|
|
---------------------------------
|
|
|
|
The `static-selector-jms` example shows you how to configure a ActiveMQ
|
|
queue with static message selectors (filters) using JMS.
|
|
|
|
Stomp
|
|
-----
|
|
|
|
The `stomp` example shows you how to configure a ActiveMQ server to send
|
|
and receive Stomp messages.
|
|
|
|
Stomp1.1
|
|
--------
|
|
|
|
The `stomp` example shows you how to configure a ActiveMQ server to send
|
|
and receive Stomp messages via a Stomp 1.1 connection.
|
|
|
|
Stomp1.2
|
|
--------
|
|
|
|
The `stomp` example shows you how to configure a ActiveMQ server to send
|
|
and receive Stomp messages via a Stomp 1.2 connection.
|
|
|
|
Stomp Over Web Sockets
|
|
----------------------
|
|
|
|
The `stomp-websockets` example shows you how to configure a ActiveMQ
|
|
server to send and receive Stomp messages directly from Web browsers
|
|
(provided they support Web Sockets).
|
|
|
|
Symmetric Cluster
|
|
-----------------
|
|
|
|
The `symmetric-cluster` example demonstrates a symmetric cluster set-up
|
|
with ActiveMQ.
|
|
|
|
ActiveMQ has extremely flexible clustering which allows you to set-up
|
|
servers in many different topologies. The most common topology that
|
|
you'll perhaps be familiar with if you are used to application server
|
|
clustering is a symmetric cluster.
|
|
|
|
With a symmetric cluster, the cluster is homogeneous, i.e. each node is
|
|
configured the same as every other node, and every node is connected to
|
|
every other node in the cluster.
|
|
|
|
Temporary Queue
|
|
---------------
|
|
|
|
A simple example demonstrating how to use a JMS temporary queue.
|
|
|
|
Topic
|
|
-----
|
|
|
|
A simple example demonstrating a JMS topic.
|
|
|
|
Topic Hierarchy
|
|
---------------
|
|
|
|
ActiveMQ supports topic hierarchies. With a topic hierarchy you can
|
|
register a subscriber with a wild-card and that subscriber will receive
|
|
any messages sent to an address that matches the wild card.
|
|
|
|
Topic Selector 1
|
|
----------------
|
|
|
|
The `topic-selector-example1` example shows you how to send message to a
|
|
JMS Topic, and subscribe them using selectors with ActiveMQ.
|
|
|
|
Topic Selector 2
|
|
----------------
|
|
|
|
The `topic-selector-example2` example shows you how to selectively
|
|
consume messages using message selectors with topic consumers.
|
|
|
|
Transaction Failover
|
|
--------------------
|
|
|
|
The `transaction-failover` example demonstrates two servers coupled as a
|
|
live-backup pair for high availability (HA), and a client using a
|
|
transacted JMS session failing over from live to backup when the live
|
|
server is crashed.
|
|
|
|
ActiveMQ implements failover of client connections between live and
|
|
backup servers. This is implemented by the sharing of a journal between
|
|
the servers. When a live node crashes, the client connections can carry
|
|
and continue to send and consume messages. When transacted sessions are
|
|
used, once and only once message delivery is guaranteed.
|
|
|
|
Failover Without Transactions
|
|
-----------------------------
|
|
|
|
The `stop-server-failover` example demonstrates failover of the JMS
|
|
connection from one node to another when the live server crashes using a
|
|
JMS non-transacted session.
|
|
|
|
Transactional Session
|
|
---------------------
|
|
|
|
The `transactional` example shows you how to use a transactional Session
|
|
with ActiveMQ.
|
|
|
|
XA Heuristic
|
|
------------
|
|
|
|
The `xa-heuristic` example shows you how to make an XA heuristic
|
|
decision through ActiveMQ Management Interface. A heuristic decision is
|
|
a unilateral decision to commit or rollback an XA transaction branch
|
|
after it has been prepared.
|
|
|
|
XA Receive
|
|
----------
|
|
|
|
The `xa-receive` example shows you how message receiving behaves in an
|
|
XA transaction in ActiveMQ.
|
|
|
|
XA Send
|
|
-------
|
|
|
|
The `xa-send` example shows you how message sending behaves in an XA
|
|
transaction in ActiveMQ.
|
|
Core API Examples
|
|
=================
|
|
|
|
To run a core example, simply `cd` into the appropriate example
|
|
directory and type `ant`
|
|
|
|
Embedded
|
|
--------
|
|
|
|
The `embedded` example shows how to embed the ActiveMQ server within
|
|
your own code.
|