activemq-artemis/docs/user-manual/en/examples.md

Examples

The Apache ActiveMQ distribution comes with over 90 run out-of-the-box examples demonstrating many of the features.

The examples are available in the distribution, in the examples directory. Examples are split into JMS and core examples. JMS examples show how a particular feature can be used by a normal JMS client. Core examples show how the equivalent feature can be used by a core messaging client.

A set of Java EE examples are also provided which need WildFly installed to be able to run.

JMS Examples

To run a JMS example, simply cd into the appropriate example directory and type mvn verify (For details please read the readme.html in each example directory).

Here's a listing of the examples with a brief description.

JMS AeroGear

This example shows how you can send a message to a mobile device by leveraging AeroGears push technology which provides support for different push notification technologies like Google Cloud Messaging, Apple's APNs or Mozilla's SimplePush.

Applet

This example shows you how to send and receive JMS messages from an Applet.

Application-Layer Failover

Apache ActiveMQ also supports Application-Layer failover, useful in the case that replication is not enabled on the server side.

With Application-Layer failover, it's up to the application to register a JMS ExceptionListener with Apache ActiveMQ which will be called by Apache ActiveMQ in the event that connection failure is detected.

The code in the ExceptionListener then recreates the JMS connection, session, etc on another node and the application can continue.

Application-layer failover is an alternative approach to High Availability (HA). Application-layer failover differs from automatic failover in that some client side coding is required in order to implement this. Also, with Application-layer failover, since the old session object dies and a new one is created, any uncommitted work in the old session will be lost, and any unacknowledged messages might be redelivered.

Core Bridge Example

The bridge example demonstrates a core bridge deployed on one server, which consumes messages from a local queue and forwards them to an address on a second server.

Core bridges are used to create message flows between any two Apache ActiveMQ servers which are remotely separated. Core bridges are resilient and will cope with temporary connection failure allowing them to be an ideal choice for forwarding over unreliable connections, e.g. a WAN.

Browser

The browser example shows you how to use a JMS QueueBrowser with Apache ActiveMQ.

Queues are a standard part of JMS, please consult the JMS 1.1 specification for full details.

A QueueBrowser is used to look at messages on the queue without removing them. It can scan the entire content of a queue or only messages matching a message selector.

Client Kickoff

The client-kickoff example shows how to terminate client connections given an IP address using the JMX management API.

Client side failover listener

The client-side-failoverlistener example shows how to register a listener to monitor failover events

Client-Side Load-Balancing

The client-side-load-balancing example demonstrates how sessions created from a single JMS Connection can be created to different nodes of the cluster. In other words it demonstrates how Apache ActiveMQ does client-side load-balancing of sessions across the cluster.

Clustered Durable Subscription

This example demonstrates a clustered JMS durable subscription

Clustered Grouping

This is similar to the message grouping example except that it demonstrates it working over a cluster. Messages sent to different nodes with the same group id will be sent to the same node and the same consumer.

Clustered Queue

The clustered-queue example demonstrates a JMS queue deployed on two different nodes. The two nodes are configured to form a cluster. We then create a consumer for the queue on each node, and we create a producer on only one of the nodes. We then send some messages via the producer, and we verify that both consumers receive the sent messages in a round-robin fashion.

Clustering with JGroups

The clustered-jgroups example demonstrates how to form a two node cluster using JGroups as its underlying topology discovery technique, rather than the default UDP broadcasting. We then create a consumer for the queue on each node, and we create a producer on only one of the nodes. We then send some messages via the producer, and we verify that both consumers receive the sent messages in a round-robin fashion.

Clustered Standalone

The clustered-standalone example demonstrates how to configure and starts 3 cluster nodes on the same machine to form a cluster. A subscriber for a JMS topic is created on each node, and we create a producer on only one of the nodes. We then send some messages via the producer, and we verify that the 3 subscribers receive all the sent messages.

Clustered Static Discovery

This example demonstrates how to configure a cluster using a list of connectors rather than UDP for discovery

Clustered Static Cluster One Way

This example demonstrates how to set up a cluster where cluster connections are one way, i.e. server A -> Server B -> Server C

Clustered Topic

The clustered-topic example demonstrates a JMS topic deployed on two different nodes. The two nodes are configured to form a cluster. We then create a subscriber on the topic on each node, and we create a producer on only one of the nodes. We then send some messages via the producer, and we verify that both subscribers receive all the sent messages.

Message Consumer Rate Limiting

With Apache ActiveMQ you can specify a maximum consume rate at which a JMS MessageConsumer will consume messages. This can be specified when creating or deploying the connection factory.

If this value is specified then Apache ActiveMQ will ensure that messages are never consumed at a rate higher than the specified rate. This is a form of consumer throttling.

Dead Letter

The dead-letter example shows you how to define and deal with dead letter messages. Messages can be delivered unsuccessfully (e.g. if the transacted session used to consume them is rolled back).

Such a message goes back to the JMS destination ready to be redelivered. However, this means it is possible for a message to be delivered again and again without any success and remain in the destination, clogging the system.

To prevent this, messaging systems define dead letter messages: after a specified unsuccessful delivery attempts, the message is removed from the destination and put instead in a dead letter destination where they can be consumed for further investigation.

Delayed Redelivery

The delayed-redelivery example demonstrates how Apache ActiveMQ can be configured to provide a delayed redelivery in the case a message needs to be redelivered.

Delaying redelivery can often be useful in the case that clients regularly fail or roll-back. Without a delayed redelivery, the system can get into a "thrashing" state, with delivery being attempted, the client rolling back, and delivery being re-attempted in quick succession, using up valuable CPU and network resources.

Divert

Apache ActiveMQ diverts allow messages to be transparently "diverted" or copied from one address to another with just some simple configuration defined on the server side.

Durable Subscription

The durable-subscription example shows you how to use a durable subscription with Apache ActiveMQ. Durable subscriptions are a standard part of JMS, please consult the JMS 1.1 specification for full details.

Unlike non-durable subscriptions, the key function of durable subscriptions is that the messages contained in them persist longer than the lifetime of the subscriber - i.e. they will accumulate messages sent to the topic even if there is no active subscriber on them. They will also survive server restarts or crashes. Note that for the messages to be persisted, the messages sent to them must be marked as durable messages.

Embedded

The embedded example shows how to embed JMS within your own code using POJO instantiation and no config files.

Embedded Simple

The embedded example shows how to embed JMS within your own code using regular Apache ActiveMQ XML files.

Message Expiration

The expiry example shows you how to define and deal with message expiration. Messages can be retained in the messaging system for a limited period of time before being removed. JMS specification states that clients should not receive messages that have been expired (but it does not guarantee this will not happen).

Apache ActiveMQ can assign an expiry address to a given queue so that when messages are expired, they are removed from the queue and sent to the expiry address. These "expired" messages can later be consumed from the expiry address for further inspection.

Apache ActiveMQ Resource Adapter example

This examples shows how to build the activemq resource adapters a rar for deployment in other Application Server's

HTTP Transport

The http-transport example shows you how to configure Apache ActiveMQ to use the HTTP protocol as its transport layer.

Instantiate JMS Objects Directly

Usually, JMS Objects such as ConnectionFactory, Queue and Topic instances are looked up from JNDI before being used by the client code. This objects are called "administered objects" in JMS terminology.

However, in some cases a JNDI server may not be available or desired. To come to the rescue Apache ActiveMQ also supports the direct instantiation of these administered objects on the client side so you don't have to use JNDI for JMS.

Interceptor

Apache ActiveMQ allows an application to use an interceptor to hook into the messaging system. Interceptors allow you to handle various message events in Apache ActiveMQ.

JAAS

The jaas example shows you how to configure Apache ActiveMQ to use JAAS for security. Apache ActiveMQ can leverage JAAS to delegate user authentication and authorization to existing security infrastructure.

JMS Auto Closable

The jms-auto-closeable example shows how JMS resources, such as connections, sessions and consumers, in JMS 2 can be automatically closed on error.

JMS Completion Listener

The jms-completion-listener example shows how to send a message asynchronously to Apache ActiveMQ and use a CompletionListener to be notified of the Broker receiving it.

JMS Bridge

The jms-brige example shows how to setup a bridge between two standalone Apache ActiveMQ servers.

JMS Context

The jms-context example shows how to send and receive a message to a JMS Queue using Apache ActiveMQ by using a JMS Context.

A JMSContext is part of JMS 2.0 and combines the JMS Connection and Session Objects into a simple Interface.

JMS Shared Consumer

The jms-shared-consumer example shows you how can use shared consumers to share a subscription on a topic. In JMS 1.1 this was not allowed and so caused a scalability issue. In JMS 2 this restriction has been lifted so you can share the load across different threads and connections.

JMX Management

The jmx example shows how to manage Apache ActiveMQ using JMX.

Large Message

The large-message example shows you how to send and receive very large messages with Apache ActiveMQ. Apache ActiveMQ supports the sending and receiving of huge messages, much larger than can fit in available RAM on the client or server. Effectively the only limit to message size is the amount of disk space you have on the server.

Large messages are persisted on the server so they can survive a server restart. In other words Apache ActiveMQ doesn't just do a simple socket stream from the sender to the consumer.

Last-Value Queue

The last-value-queue example shows you how to define and deal with last-value queues. Last-value queues are special queues which discard any messages when a newer message with the same value for a well-defined last-value property is put in the queue. In other words, a last-value queue only retains the last value.

A typical example for last-value queue is for stock prices, where you are only interested by the latest price for a particular stock.

Management

The management example shows how to manage Apache ActiveMQ using JMS Messages to invoke management operations on the server.

Management Notification

The management-notification example shows how to receive management notifications from Apache ActiveMQ using JMS messages. Apache ActiveMQ servers emit management notifications when events of interest occur (consumers are created or closed, addresses are created or deleted, security authentication fails, etc.).

Message Counter

The message-counters example shows you how to use message counters to obtain message information for a JMS queue.

Message Group

The message-group example shows you how to configure and use message groups with Apache ActiveMQ. Message groups allow you to pin messages so they are only consumed by a single consumer. Message groups are sets of messages that has the following characteristics:

• Messages in a message group share the same group id, i.e. they have same JMSXGroupID string property values

• The consumer that receives the first message of a group will receive all the messages that belongs to the group

Message Group

The message-group2 example shows you how to configure and use message groups with Apache ActiveMQ via a connection factory.

Message Priority

Message Priority can be used to influence the delivery order for messages.

It can be retrieved by the message's standard header field 'JMSPriority' as defined in JMS specification version 1.1.

The value is of type integer, ranging from 0 (the lowest) to 9 (the highest). When messages are being delivered, their priorities will effect their order of delivery. Messages of higher priorities will likely be delivered before those of lower priorities.

Messages of equal priorities are delivered in the natural order of their arrival at their destinations. Please consult the JMS 1.1 specification for full details.

Multiple Failover

This example demonstrates how to set up a live server with multiple backups

Multiple Failover Failback

This example demonstrates how to set up a live server with multiple backups but forcing failover back to the original live server

No Consumer Buffering

By default, Apache ActiveMQ consumers buffer messages from the server in a client side buffer before you actually receive them on the client side. This improves performance since otherwise every time you called receive() or had processed the last message in a MessageListener onMessage() method, the Apache ActiveMQ client would have to go the server to request the next message, which would then get sent to the client side, if one was available.

This would involve a network round trip for every message and reduce performance. Therefore, by default, Apache ActiveMQ pre-fetches messages into a buffer on each consumer.

In some case buffering is not desirable, and Apache ActiveMQ allows it to be switched off. This example demonstrates that.

Non-Transaction Failover With Server Data Replication

The non-transaction-failover example demonstrates two servers coupled as a live-backup pair for high availability (HA), and a client using a non-transacted JMS session failing over from live to backup when the live server is crashed.

Apache ActiveMQ implements failover of client connections between live and backup servers. This is implemented by the replication of state between live and backup nodes. When replication is configured and a live node crashes, the client connections can carry and continue to send and consume messages. When non-transacted sessions are used, once and only once message delivery is not guaranteed and it is possible that some messages will be lost or delivered twice.

OpenWire

The Openwire example shows how to configure an Apache ActiveMQ server to communicate with an Apache ActiveMQ JMS client that uses open-wire protocol.

Paging

The paging example shows how Apache ActiveMQ can support huge queues even when the server is running in limited RAM. It does this by transparently paging messages to disk, and depaging them when they are required.

Pre-Acknowledge

Standard JMS supports three acknowledgement modes: AUTO_ACKNOWLEDGE, CLIENT_ACKNOWLEDGE, and DUPS_OK_ACKNOWLEDGE. For a full description on these modes please consult the JMS specification, or any JMS tutorial.

All of these standard modes involve sending acknowledgements from the client to the server. However in some cases, you really don't mind losing messages in event of failure, so it would make sense to acknowledge the message on the server before delivering it to the client. This example demonstrates how Apache ActiveMQ allows this with an extra acknowledgement mode.

Message Producer Rate Limiting

The producer-rte-limit example demonstrates how, with Apache ActiveMQ, you can specify a maximum send rate at which a JMS message producer will send messages.

Proton Qpid

Apache ActiveMQ can be configured to accept requests from any AMQP client that supports the 1.0 version of the protocol. This proton-j example shows a simply qpid java 1.0 client example.

Proton Ruby

Apache ActiveMQ can be configured to accept requests from any AMQP client that supports the 1.0 version of the protocol. This example shows a simply proton ruby client that sends and receives messages

Queue

A simple example demonstrating a JMS queue.

Message Redistribution

The queue-message-redistribution example demonstrates message redistribution between queues with the same name deployed in different nodes of a cluster.

Queue Requestor

A simple example demonstrating a JMS queue requestor.

Queue with Message Selector

The queue-selector example shows you how to selectively consume messages using message selectors with queue consumers.

Reattach Node example

The Reattach Node example shows how a client can try to reconnect to the same server instead of failing the connection immediately and notifying any user ExceptionListener objects. Apache ActiveMQ can be configured to automatically retry the connection, and reattach to the server when it becomes available again across the network.

Replicated Failback example

An example showing how failback works when using replication, In this example a live server will replicate all its Journal to a backup server as it updates it. When the live server crashes the backup takes over from the live server and the client reconnects and carries on from where it left off.

Replicated Failback static example

An example showing how failback works when using replication, but this time with static connectors

Replicated multiple failover example

An example showing how to configure multiple backups when using replication

Replicated Failover transaction example

An example showing how failover works with a transaction when using replication

Request-Reply example

A simple example showing the JMS request-response pattern.

Rest example

An example showing how to use the Apache ActiveMQ Rest API

Scheduled Message

The scheduled-message example shows you how to send a scheduled message to a JMS Queue with Apache 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 Apache ActiveMQ.

Send Acknowledgements

The send-acknowledgements example shows you how to use Apache 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 Apache ActiveMQ's Spring integration.

SSL Transport

The ssl-enabled shows you how to configure SSL with Apache ActiveMQ to send and receive message.

Static Message Selector

The static-selector example shows you how to configure an Apache ActiveMQ core queue with static message selectors (filters).

Static Message Selector Using JMS

The static-selector-jms example shows you how to configure an Apache ActiveMQ queue with static message selectors (filters) using JMS.

Stomp

The stomp example shows you how to configure an Apache ActiveMQ server to send and receive Stomp messages.

Stomp1.1

The stomp example shows you how to configure an Apache ActiveMQ server to send and receive Stomp messages via a Stomp 1.1 connection.

Stomp1.2

The stomp example shows you how to configure an Apache 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 an Apache 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 Apache ActiveMQ.

Apache 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

Apache 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 Apache 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.

Apache 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 Apache ActiveMQ.

XA Heuristic

The xa-heuristic example shows you how to make an XA heuristic decision through Apache 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 Apache ActiveMQ.

XA Send

The xa-send example shows you how message sending behaves in an XA transaction in Apache 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 Apache ActiveMQ server within your own code.