JMSSession1TP-final.ppt

JMS / Session 1 / 2 of 36
Session Objectives
 Describe messaging
 Discuss JMS and the different scenarios
where it can be used
 Explain the JMS architecture
 JMS components
 Approaches for implementing JMS
 JMS programming model

Tightly Coupled Systems
Active connection
Component 1 Component 2
Receiver receives
the data
Communication takes place
Sender sends
the data
Inactive connection
Component 1
Communication
does not take place
Component 2
Sender sends
the data
Receiver not
available

Loosely Coupled Systems
Component 1
Communication
still takes place
Component 2
Inactive connection
Sender sends
the data
Receiver receives
the data
Receiver not
available
Active connection
Component 1 Component 2
Receiver receives
the data
Communication takes place
Sender sends
the data

Communication
Refers to the process of exchanging data between
entities
Types
Synchronous
Communication
Asynchronous
Communication

Synchronous Communication
Request
Response
Client
Server
Client
waits for
server
response

Asynchronous Communication
Request
Client
Server
Client
does not
wait for
server
response

Messaging (1)
Can send and receive
data from other
messaging clients
Can send and receive
data from other
messaging clients
Messaging System
(MOM)
Messaging Client
acting as a Sender
Messaging Client
acting as a Receiver
Destination
A message is an
encapsulated set
of data
Provides facilities for
creating, sending,
receiving and reading
messages

Messaging (2)
 Components are loosely coupled
 Application components need to continuously
communicate irrespective of component
availability
 Communication is asynchronous
Messaging can be used when:
MOM
Receiver
Destination
Sender

Messaging (3)
 Components exchanging messages need not
be available at the same time
 Messages translated while being transmitted
 Asynchronous communication
 One message received by multiple receivers
Advantages:
MOM
Receiver
Destination
Sender

Messaging (4)
 Not the best choice for highly interactive
components
 Information on message handling is not
available
Limitations:
MOM
Receiver
Destination
Sender

Java Message Service
Helps build asynchronous message-oriented
applications
Not a messaging system but an API
Allows application developers to create, send, receive
and read messages

Application Scenario for using
JMS API (1)
Component 2
Component 1
Communication
still takes place
Inactive connection
Sender sends the
data
Receiver receives
the data
Loosely coupled components
Request
Client
Server
Client
does not
wait for
server
response
Asynchronous Communication

Application Scenario for using
JMS API (2)
Sender Receivers
One sender – multiple receivers
Personal
Computer
Mainframe
Legacy systems communicating with new systems

Applications using JMS API (1)
Inventory
Component
Manufacturing
Unit
Component
Parts
Component
Parts Order
Component
Parts
Inventory
Component
Inventory Management System:

Applications using JMS API (2)
HR Component
Accounts
Component
Administration
Component
Human Resource Management System:

JMS Architecture
JMS
Components
Messaging
Domains
JMS
Programming
Model

JMS Components
JMS Client 1
JMS Provider (MOM)
JNDI
Connection
Factories
Destinations
JMS Client 4
JMS Client 3
JMS Client 2
1
2
3
4

JMS Messaging Models
Point-to-Point Publish/Subscribe
JMS specifications provide different messaging
domains for each of the models

Publish/Subscribe (pub/sub)
Publisher
Subscriber
Subscriber
Subscriber
JMS
Provider
Topic
1
1 – Publish Messages to the topic
2 – Subscribe to the topic for Messages
This approach is intended for a One-to-Many
scenario
2
2
2

Point-to-Point (p2p)
1 – Message sent to queue
2 – Message fetched from queue
Sender
JMS
Provider
Receiver
1 Queue
This approach is intended for a One-to-One scenario
2

JMS Programming Model
The steps are as follows…

Step 1: Get the JNDI Context
Through jndi.properties file
java.naming.factory.initial=
org.jnp.interfaces.NamingContextFactory
java.naming.provider.url=localhost:1099
java.naming.factory.url.pkgs=
org.jboss.naming:org.jnp.interfaces
Creating the jndi.properties
Context context = new InitialContext();
Obtain the JNDI context in the client’s code
(First method)

Step 1: Get the JNDI Context
Hashtable properties = new Hashtable();
properties.put(Context.INITIAL_CONTEXT_FACTORY,
"org.jnp.interfaces.NamingContextFactory");
properties.put(Context.PROVIDER_URL, "localhost:1099");
properties.put("java.naming.rmi.security.manager", "yes");
properties.put(Context.URL_PKG_PREFIXES,
"org.jboss.naming");
Manually setting the JNDI
(Second method)

Step 2: Look up a Connection
Factory
// Get the topic connection factory
TopicConnectionFactory tConFactory =
(TopicConnectionFactory)context.lookup("ConnectionFactory");
// Get the queue connection factory
QueueConnectionFactory qConFactory =
(QueueConnectionFactory)context.lookup("ConnectionFactory");
Connection factories are used by the clients to get a
connection with the JMS provider
Or

Step 3: Obtain a Connection
Connection objects represent a connection with the
JMS provider and are used to create session object(s)
// Get the connection object for topic
TopicConnection tCon = tConFactory.createTopicConnection();
// Get the connection object for queue
QueueConnection qCon = qConFactory.createQueueConnection();
tCon.close(); qCon.close();
Close the connection object
Or
Or

Step 4: Create a Session
Session is used for producing and consuming messages
// Create a TopicSession object using TopicConnection
TopicSession tSession =
tCon.createTopicSession(false,Session.AUTO_ACKNOWLEDGE);
// Create a QueueSession object using QueueConnection
QueueSession qSession = qCon.createQueueSession(true, 0);
Or

Step 5: Look up the
Destination
// Look up the topic destination
Topic newTopic =
(Topic)context.lookup("topic/testTopic");
// Look up the queue destination
Queue newQ = (Queue)context.lookup("queue/testQueue");
Destinations specify the target for message
producers and source for message consumers
Or

Step 6A: Create a Message
Producer
// Create a publisher for the topic, newTopic
TopicPublisher tPublisher = tSession.createPublisher(newTopic);
// Create a sender for the queue, newQ
QueueSender qSender = qSession.createSender(newQ);
Message producer is created by the session and is
used for sending messages to a destination
Or

Step 6B: Create a Message
Consumer
// Create a subscriber for the topic, newTopic
TopicSubscriber tSubscriber =
tSession.createSubscriber(newTopic);
// Create a receiver for the queue, newQ
QueueReceiver qRcvr = qSession.createReceiver(newQ);
Message consumer is created by the session and they
are the receiver of the messages
Or

Step 7A: Publish / Send
Messages
// Publish a message using TopicPublisher
tPublisher.publish(msg);
// Send a message using QueueSender
qSender.send(msg);
Or

Step 7B: Receive Messages
Receive messages synchronously
tCon.start();
Message msg =
tSubscriber.receive(1000);
qCon.start();
Message msg =
qRcvr.receive();
Receive messages asynchronously
TopicListener tListener = new TopicListener();
/* TopicListener is a user-defined class implementing
MessageListener interface */
tSubscriber.setMessageListener
(tListener);
qRcvr.setMessageListener
(tListener);
Or
Or

JMS Programming Model
Summary of steps
7. Send or receive messages
1. Get the JNDI Context
2. Look up a connection factory
3. Obtain a connection
5. Look up the destination
6. Create a message producer and a message consumer
4. Create a session

Messages
Message
Header Message
Properties
Message
Bodies
Contains pre-
defined fields to
identify and route
messages
Created for messages
requiring additional values
apart from those provided
by header fields
JMS API provides
various body
formats or
message types

Message Header

Message Types

JMSSession1TP-final.ppt

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