Java Messaging Service

1
Java Messaging Service

• Notes prepared from GBC Professional Development
  Seminar Understanding the Java Messaging Service
  David Chappell Rick Kuzyk, Sonic Software.

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Messaging

• Data exchange requirements between disparate
  applications
• B2C components (and clients)
• catalogs
• order
• payment
• fulfillment
• support

3
Messaging

• Data exchange requirements between disparate
  applications
• B2B components (and clients)
• wholesale??retail
• accounts payable and receivable
• Disconnected users (mobile, handheld)
• package delivery
• maintenance
• web phones

4
Messaging

• Data exchange requirements between disparate
  applications
• B2B components (and clients)
• wholesale??retail
• accounts payable and receivable
• Disconnected users (mobile, handheld)
• package delivery
• maintenance
• web phones

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Enterprise Messaging (MOM)

• Message oriented middleware (MOM)
• Asynchronous messaging sender need not wait for
  reply
• decoupled sender and receiverno direct
  communication
• no persistent connection between parties,
  including MOM

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Enterprise Message vs RPC
Enterprise Messaging RPC
Asynchronous Synchronous (Req/Rpy)
Tolerates partial failure Partial failure can affect entire application
Transparent support for distributed systems Best for single, possibly n-tiered, system
Indirect communication through MOM Direct communication between processes
Applications decoupled Applications coupled
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Enterprise messaging
Application A
Application A
MOM
Messaging API
Messaging API
Messaging Clients
Messaging Clients
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Tightly coupled RPC
App C
App A
n(n-1)/2 connections
RPC infrastructure
RPC infrastructure
App D
RPC infrastructure
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JMS Messaging
JMS Client
JMS Client
JMS Client
Router
Local "server"
Message server
JMS Client
JMS Client
JMS Client
JMS Client
JMS Client
JMS Client
Local "server"
Local "server"
Decentralized (IP multicast)
Hub and spoke
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JMS

• JMS Messaging client
• Uses the JMS API to create, send, receive
  messages
• Interfaces and classes or the API client
  runtime
• JMS Message server
• handles deliver of messages sent by clients to
  other messaging clients who register an interest
• JMS provider JMS client runtime message
  server.
• supports the JMS API and reliable delivery
• J2EE provides glue that lets certain objects to
  run as a JMS messaging client

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JMS and J2EE

• These objects can function as JMS messaging
  clients via J2EE
• enterprise beans (EJB)
• servlets
• JSP pages
• J2EE application client
• message-driven bean an EJB that can consume JSP
  messages

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J2EE
Client application
EJB Container
Application Client Container
Web Container
J2EE platform
JMS Server
JDBC Server
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JMS Client classes
Connection Binds a JMS client to a message server. multiple per client associated with either pub/sub or PTP
Session Context for sending/receiving messages multiple per Connection
Producer sends messages to Destinations
Destination identifier for a message
Message package sent from a producer to a consumer
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JMS Components
Message server
Destination
Message
Message
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JMS Components
JMS Client
JMS Client
Consumer
Producer
Bind to Destination
Bind to Destination
Message server
Destination
SendMessage
ConsumeMessage
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JMS Client objects

• Producer
• Binds to a destination to send messages
• Determines message TTL, priority, persistence
• Consumer
• Binds to a destination to receive messages
• Receives messages asynchronously through a
  message listener or synchronously by polling

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JMS Client objects

• Messages
• Headers
• Property list (some predefined) Consumers can
  select on properties
• Body

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JMS Message types
Message type Body
Message Empty
TextMessage Java String
ObjectMessage Serializable Java object
MapMessage Name/value pairs
StreamMessage Stream of Java primitives
BytesMessage Uninterpreted bytes
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Messaging Domains

• Publish and subscribe (pub/sub)
• Many consumers per message
• Messages have a topic that identifies the
  relation of publisher to subscriber
• Point-to-point (PTP, p2p)
• One consumer per message
• Messages queued. Consumers can browse queue
  without consuming

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Pub/Sub model
Publisher
Topic
Subscriber
New books
HW
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P2P model
Sender
Que
Receiver
Submit
Grade
PARTY!
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Connections and sessions

• jndi new InitialCOntext(env)tFactory
  (TopicConnectionFactory)jndi.lookup("TopicConne
  ctionFactory")qFactory QueueConnectionFactory
  )jndi.lookup("QueueConnectionFactory")
• tConnect tFactory.createTopicConnection(unserna
  me, password)qConnect qFactory.createQueueConn
  ection(unsername, password)
• tSession
• tConnect.createTopicSession(false,
  Session.AUTO_ACKNOWLEDGE)qSession
• qConnect.createQueueSession(false,
  Session.AUTO_ACKNOWLEDGE)
• tConnect.start()
• qConnect.start()

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Destinations

• Pub/sub topics
• May be predetermined by server
• May be created on a server by a JMS client
• Topic hw9Topic tSession.createTopic("hw9")
• May be looked up in a db via Java Naming and
  Directory Interface (JNDI)
• Topic hw9Topic (Topic)jndi.lookup("hw9")

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Destinations

• P2P queues
• Queue must exist in server
• Queue hwQ tSession.createQueue("HW") // or
• Queue hwQ (Queue) jndi.lookup("HW")

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Creating and populating a message
Queue SessionqSession
qSession.createTextMessage()
Text MessagetextMsg
String thisHW"hw9"textMsg.createContent("GreatJ
ob on" thisHW)
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JMS message headers

• Assigned by system
• JMSDestination
• JMSDeliveryMode
• JMSMessageID
• JMSTimestamp
• JMSExpiration
• JMS Priority

• Assigned by developer
• JMSReplyTo
• JMSCorrelationID
• JMSType

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Message properties

• Name/value pairs assigned by application
• Values must be Java primitives
• Setting
• message.setStringProperty("studentName", "Nemo")
  //prop
• message.setJMSReplyTo(hw9Q) //header
• Can filter on props or headers
• javax.jms.QueueReceiver rcvr
  qSession.createReceiver(hw9Q, "JMSPriority gt
  10")