Short presentation of JMS features and concepts.

1. JMS
Prepared by: Andrey Stelmashenko

2. What is JMS?
● A specification that describes a common way for Java
programs to create, send, receive and read distributed
enterprise messages;
● loosely coupled communication;
● Asynchronous messaging;
● Reliable delivery;
– A message is guaranteed to be delivered once
and only once.
● Outside the specification
– Security services
– Management services

3. Goals
● Provide a single, unified message API
● Minimize knowledge needed for programmers
needed to write clients
● Utilize concepts of message exchange
applications
● Simplify portability of JMS clients

4. JMS Application

5. JMS Concepts
● Connection factory
● Connection
● Session
● Message producer
● Destination
● Message consumer
● Message

6. Responsibilities
Client side:
JMS Provider:
● Message producer
● Connection factory
● Message consumer
● Connection
● Message
● Destination
● Session

7. Example

8. Message producer

9. @Resource(name = "jmsPool1")
private ConnectionFactory connectionFactory;
@Resource(name = "jndiJmsDest1")
private Destination dest;
@Override
protected void doGet(...) {
Connection connection = null;
MessageProducer producer = null;
try {
connection = connectionFactory.createConnection();
Session session = connection.createSession(false,
Session.AUTO_ACKNOWLEDGE);
producer = session.createProducer(dest);
TextMessage message = session.createTextMessage();
message.setText("Hello, JMS!!!");
producer.send(message);
} catch (JMSException e) {...}
try {
connection.close();
} catch (JMSException e) {...}
...

10. @Resource(name = "jmsPool1")
private ConnectionFactory connectionFactory;

11. @Resource(name = "jmsPool1")
private ConnectionFactory connectionFactory;
@Resource(name = "jndiJmsDest1")
private Destination dest;

12. @Resource(name = "jmsPool1")
private ConnectionFactory connectionFactory;
@Resource(name = "jndiJmsDest1")
private Destination dest;
@Override protected void doGet(...) {
Connection connection = null;
MessageProducer producer = null;
try {
1 connection = connectionFactory.createConnection();
2 Session session = connection.createSession(false,
Session.AUTO_ACKNOWLEDGE);
3 producer = session.createProducer(dest);
4 TextMessage message = session.createTextMessage();
5 message.setText("Hello, JMS!!!");
6 producer.send(message);
} catch (JMSException e) {...}
try {
connection.close();
} catch (JMSException e) {...}
...

13. Message consumer

14. @Resource(name = "jmsPool2")
private ConnectionFactory connectionFactory;
@Resource(name = "jndiJmsDest1")
private Destination dest;

15. @Resource(name = "jmsPool2")
private ConnectionFactory connectionFactory;
@Resource(name = "jndiJmsDest1")
private Destination dest;
@Override protected void doGet(...) {
Connection connection = null;
Session session = null;
MessageConsumer consumer = null;
TextMessage message = null;
try {
1 connection = connectionFactory.createConnection();
2 session = connection.createSession(false,
Session.AUTO_ACKNOWLEDGE);
3 consumer = session.createConsumer(dest);
4 connection.start();
5 Message m = consumer.receive();
6 message = (TextMessage) m;
7 LOG.info("Msg: " + message.getText());
} catch (JMSException e) {…}
finally {
connection.close();
}
...

16. Where are Connection Factory and
Destination?

17. JMS Application
A JMS application is composed of the following parts:
• JMS Clients - These are the Java language programs that send
and receive messages.
• Non-JMS Clients.
• Messages - Each application defines a set of messages that are
used to communicate information between its clients.
• JMS Provider - This is a messaging system that implements
JMS in addition to the other administrative and control
functionality required of a full-featured messaging product.
• Administered Objects - Administered objects are preconfigured
JMS objects created by an administrator for the use of clients.

18. Administered objects
Two types of JMS administered objects:
• ConnectionFactory - This is the object a client
uses to create a connection with a provider.
• Destination - This is the object a client uses to
specify the destination of messages it is sending
and the source of messages it receives.

19. JMS Administration

22. Domains
There are two models of interaction:
● In the point-to-point (or PTP) messaging
model, each message is delivered from a
message producer to a single message
consumer.
● In the publish/subscribe (or pub/sub) model, a
single message can be delivered from a
producer to any number of consumers.

23. PTP

24. Pub / Sub

25. PTP and Pub/Sub Interfaces

26. Session
● A session is a single-threaded context for
producing and consuming messages.
● Sessions are the JMS entity that supports
transactions.
– A JMS client may use JTA to delimit distributed
transactions; however, this is a function of the transaction
environment the client is running in. It is not a feature of
JMS.

27. Messages
Composed of:
● Header
used by both clients and providers to identify and route messages
● Properties
– Application-specific properties
– Standard properties
– Provider-specific properties
● Body

28. Message Header Properties

29. Message Selection
● By headers and properties
not delivered differ a bit depending on the MessageConsumer
● Based on SQL92 conditional expression
syntax
"JMSType = ’car’ AND color = ’blue’ AND weight > 2500"

30. Message Types
● StreamMessage
● MapMessage
● TextMessage
● ObjectMessage
● BytesMessage

31. Message Acknowledgmnent
Acknowledgment handled automatically if session is transacted.
Other way three types:
● DUPS_OK_ACKNOWLEDGE
● AUTO_ACKNOWLEDGE
● CLIENT_ACKNOWLEDGE

32. Delivery Mode
● NON_PERSISTENT
delivers at-most-once. Msg may be losed.
● PERSISTENT
once-and-only-once. Msg must not delivered twice.

33. Message Scheduling

34. Message Scheduling
● No message scheduling in specification!

35. Apache ActiveMQ
ActiveMQ from version 5.4 has an optional persistent scheduler built into the ActiveMQ
message broker. It is enabled by setting the broker schedulerSupport attribute to true in
the Xml Configuration.
An ActiveMQ client can take advantage of a delayed delivery by using the following
message properties.
Property name type description
AMQ_SCHEDULED_DELAY long The time in milliseconds that a message
will wait before being scheduled to be
delivered by the broker
AMQ_SCHEDULED_PERIOD long The time in milliseconds to wait after the
start time to wait before scheduling the
message again
AMQ_SCHEDULED_REPEAT int The number of times to repeat
scheduling a message for delivery
AMQ_SCHEDULED_CRON String Use a Cron entry to set the schedule

36. ActiveMQ Example
MessageProducer producer = session.createProducer(destination);
TextMessage message = session.createTextMessage("test msg");
long time = 60 * 1000;
message.setLongProperty(
ScheduledMessage.AMQ_SCHEDULED_DELAY, time);
producer.send(message);

37. Questions