Understanding the Java Message Service

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Understanding the Java Message Service
Andreas Taber Systems Engineer Sonic Software
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Overview

• Describe the concepts and some practical
  applications of messaging.
• Describe the concepts and basic structure of JMS.
• Write simple JMS messaging code using the publish
  and subscribe and point-to-point domains.
• Discuss advanced JMS issues such as guaranteed
  messaging, transactions, reliability, and
  recovery.

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Part 1 Enterprise Messaging and JMS
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Enterprise messaging
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Tightly Coupled RPC
Requires n (n-1) / 2 connections
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JMS messaging

• Centralized message server (hub and spoke)

Decentralized message server (IP multicast)
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The J2EE platform
J2EE Platform
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JMS and Web Services

• Program internet clients with standardized JMS
  and JAXM interface
• Send SOAP, ebXML, and custom XML messages through
  the internet
• Route internet messages to the enterprise message
  bus
• Use XSLT to transform messages to standard
  formats
• Deliver messages to JMS applications for
  processing

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Part 2 JMS Concepts and Coding
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Wholesaler and retailer
Update price (publish)
Message Server
Order product (send)
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JMS features

• Standard Java API
• Message delivery modes
• Two messaging models
• Transactions
• Reliability levels
• Persistent messaging

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JMS messaging domains

• Publish and subscribe
• Many consumers per message
• Point-to-point
• One consumer per message

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Publish and subscribe Supply chain management
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Point-to-point Order and fulfillment
Queue
Receiver
Need Supplies
Goods Shipped
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JMS components
JMS Client
JMS Client
Connection
Connection
Session
Session
Producer
Consumer
Message Server
Message
Destination
Message
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Connections and sessions
JMS Client

• A connection connects to a message server.
• You can create one or more sessions within a
  connection.

Connection
Session
Session
Session
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Creating connections and sessions
JMS Client
ConnectionFactory
create
JNDI Store
Message Server
Connection
ConnectionFactories Destinations
Session
Session
Session
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JMS message types
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Creating a message
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JMS message headers

• Automatically assigned headers
• JMSDestination
• JMSDeliveryMode
• JMSMessageID
• JMSTimestamp
• JMSExpiration
• JMSRedelivered
• JMSPriority

• Developer-assigned headers
• JMSReplyTo
• JMSCorrelationID
• JMSType

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Producers, consumers, and destinations
Producer
Consumer
Bind to destination
Bind to destination
Read message
Message Server
Send message
Consume message
Destination
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Creating destinations
JMS Client
JNDI Store
Message Server
Topic
ConnectionFactories Destinations
lookup
Queue
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Producing a message
create message
Session
create
Message
Destination
MessageProducer
produce message
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Consuming messages
Incoming messages
acknowledge
Message Server
Incoming messages
acknowledge
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Asynchronous message delivery
MessageListener
onMessage(message)
Message Server
Incoming messages
acknowledge
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Using receive( )
MessageConsumer
Message receive()
Message Server
Incoming messages
acknowledge
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Filtering with message selector
Publisher
Departments.Sales
JMSPriority 2 Pipeline 20000
not delivered
Subscriber
delivered
Subscriber
Message Server
Departments.Sales Pipeline gt 20000
Departments.Sales Pipeline gt 15000
not delivered
delivered
Subscriber
Subscriber
Departments.Sales JMSPriority gt 5
Departments.Sales JMSPriority gt 2 AND Pipeline gt
10000
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Browsing a queue
Message1
QueueBrowser
Message2
getEnumeration()
Message3
Enumeration
nextElement()
Message4
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Accessing message content
Message
getlttypegt(Name)
TextMessage
MapMessage
ObjectMessage
StreamMessage
BytesMessage
getText()
getObject()
readlttypegt()
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Part 3 Guaranteed messaging
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Guaranteeing message delivery
Durable Subscriber Or QueueReceiver
PERSISTENT message
Message Server
Producer
Acknowledge message
Persistent store
Message removed after acknowledgment
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Persistent and non-persistent messages
Non-persistent message not guaranteed to survive
provider failure
Message Server
Persistent message guaranteed to survive provider
failure
Persistent store
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Acknowledgement modes
Consumer
Server
AUTO
CLIENT
DUPS_OK
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Durable subscribers
Durable Subscriber1 (connected)
PERSISTENT message
Message Server
Publisher
Durable Subscriber2 (not connected)
Persistent store
Undelivered messages delivered to Subscriber2
when reconnected
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Redelivered messages

• Before message server receives acknowledgement
• Message server has failed and restarted
• OR
• Consumer has failed and restarted

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Part 4 Transactions and recovery
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Transacted session Producer
Before commit( )
Message Server
Producer
Transacted session
Upon commit( )
Message Server
Consumer
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Transacted session Consumer
Before commit( )
Message Server
Consumer
Deliver messages
Consume messages
Upon commit( )
Message Server
Consumer
Acknowledge messages
Delete messages if all recipients have
acknowledged
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Distributed transaction support
JMS Client
XAConnectionFactory
create
JNDI Store
Message Server
XAConnection
ConnectionFactories Destinations
XASession
XASession
XASession
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Recovering from a lost connection
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Understanding the Java Message Service Conclusion