gidon gershinsky

IBM Labs in HaifaCopyright 2002-2003

IBM Corporation

Enterprise Messaging and Data Access

Advanced Web Applications DevelopmentTechnion CS 236606 Spring 2003, Class 3

Gidon Gershinsky

IBM Labs in Haifa

Copyright 2002-2003 IBM Corporation2

Overview

JMS, JNDI, JDBC Enterprise Messaging

Traditional network communication Messaging paradigm

Message-Oriented Middleware Publish/Subscribe messaging Point-to-Point messaging Architecture

Centralized Multicast Hybrid

Samples, JNDI (java naming & directory interface) Assured delivery

Durable subscription Persistent publishing Acknowledged delivery

IBM Labs in Haifa


Overview (cont)

Enterprise Application Integration (EAI) JDBC

IBM Labs in Haifa


Traditional networking

Datagram protocols: IP, UDP Streaming protocols: TCP RPC: RMI, CORBA

Synchronous Tightly coupled

(full knowledge, inc address, protocol, etc,of the communication peer(s))

IBM Labs in Haifa


Messaging

“e-mail for applications”

Asynchronous communication:The sender and receiver do not have to be available at the same time in order to communicate.

Loosely coupled:The sender does not need to know anything about the receiver, nor does the receiver need to know anything about the sender; they only need to know what message format and what destination to use.

Utilizes the TCP, UDP unicast/multicast, HTTP, etc.

IBM Labs in Haifa


Messaging

Message: “a package of business data that is sent from one application to another over the network. Self-describing – contains all the necessary context to allow the recipients to carry out their work independently”

Different from a “datagram”: Few bytes to few megabytes (UDP: up to 64K) More structured (headers, properties, body types)

Different from a “stream”

Different from file delivery

IBM Labs in Haifa


Message-Oriented Middleware (MOM)

Asynchronous,loosely coupled messaging

Fault tolerance Load balancing Scalability Transactional support

JMS Terminology:“Vendor”, “Provider”, “Client”, “Destination”,“Producer”, “Consumer”

IBM Labs in Haifa


What is JMS

Java Message Service:A Java API that allows applications to create, send, receive, and read messages

Interface specification only

Vendor-agnosticApplication developers reuse the same API to access different MOM vendors.IBM MQSeries, Tibco, SpiritSoft, Fiorano, SoftwiredMicrosoft MSMQ

No vendor interoperability:API is the same, but two implementations wont talk to each other.

Implementation switch: Little or no change in application code is requiredNo “standard compliance” body

IBM Labs in Haifa


JMS Domains

Publish/Subscribe“One-to-many” or “Many-to-many”Many consumers per message

Point-to-PointOne consumer per message

IBM Labs in Haifa


Publish/Subscribe Messaging

Topic – “destination” (virtual data channel)

Producer is a “publisher”Consumer is a “subscriber”

Publishers and subscribers are generally anonymous

Default” “Push” mode

IBM Labs in Haifa


Publish/Subscribe Messaging

Topics retain messages only as long as it takes to distribute them to current subscribers.

There is a timing dependency between publishers and subscribers, because a client that subscribes to a topic can consume only messages published after the client has created a subscription, and the subscriber must continue to be active in order for it to consume messages.

The JMS API relaxes this timing dependency to some extent by allowing clients to create durable subscriptions.

Use pub/sub messaging when each message can be processed by zero, one, or many consumers.

IBM Labs in Haifa


Point-to-Point Messaging

Queue: virtual data channel (“destination”) Producer is a “sender”

Consumer is a “receiver” “Pull” mode

IBM Labs in Haifa


Point-to-Point Messaging

Each message is addressed to a specific queue, and receiving clients extract messages from the queue(s) established to hold their messages. Queues retain all messages sent to them until the messages are consumed or until the messages expire.

Each message has only one consumer.

There are no timing dependencies between a sender and a receiver of a message. The receiver can fetch the message whether or not it is running when the client sends the message.

The receiver acknowledges the successful processing of a message.

Use PTP messaging when every message you send must be processed successfully by one consumer.

IBM Labs in Haifa


Architecture type: Centralized

Message “server”, “router” or “broker” Decouples clients: see only the server, not other clients. Allows to add/remove clients without impacting

the system. “Hub-and-spoke” topology “Message server” may be a cluster of distributed servers operating as a single logical unit.

IBM Labs in Haifa


Architecture type: Multicast

No central server Based on “IP multicast” Network layer handles routing automatically Server-like functionality at each client

IBM Labs in Haifa


Architecture type: Hybrid

Both TCP/IP and IP multicast in use

IBM Labs in Haifa


JMS Application Samples:Simple message producer, consumer

IBM Labs in Haifa


JMS example: P2P Sender (1/3)

import javax.jms.*; import javax.naming.*;

public class SimpleQueueSender {public static void main(String[] args) {

String queueName = null; Context jndiContext = null; QueueConnectionFactory queueConnectionFactory = null; QueueConnection queueConnection = null; QueueSession queueSession = null; Queue queue = null; QueueSender queueSender = null; TextMessage message = null; final int NUM_MSGS; final String MSG_TEXT = new String("Here is a message");

Properties env = new Properties();// Specify the vendor-specific JDNI properties

IBM Labs in Haifa



queueName = “Test Queue”;

/* * Create a JNDI InitialContext object */ try {

jndiContext = new InitialContext(env); } catch (NamingException e) {

System.out.println("Could not create JNDI " + "context: " + e.toString()); System.exit(1);

}

/* * Look up connection factory and queue. If either does * not exist, exit. */ try {

queueConnectionFactory = (QueueConnectionFactory) jndiContext.lookup("QueueConnectionFactory");

queue = (Queue) jndiContext.lookup(queueName); } catch (NamingException e) {

System.out.println("JNDI lookup failed: " + e.toString()); System.exit(1);

}

IBM Labs in Haifa



try { queueConnection =

queueConnectionFactory.createQueueConnection(); queueSession = queueConnection.createQueueSession(false,

Session.AUTO_ACKNOWLEDGE); queueSender = queueSession.createSender(queue);

message = queueSession.createTextMessage();

for (int i = 0; i < NUM_MSGS; i++) { message.setText(MSG_TEXT + " " + (i + 1)); System.out.println("Sending message: " +

message.getText()); queueSender.send(message);

}} catch (JMSException e) {

System.out.println("Exception occurred: " + e.toString()); }

IBM Labs in Haifa


JMS example: P2P Receiver (1/3)


public class SimpleQueueReceiver {public static void main(String[] args) {

String queueName = null; Context jndiContext = null; QueueConnectionFactory queueConnectionFactory = null; QueueConnection queueConnection = null; QueueSession queueSession = null; Queue queue = null; QueueReceiver queueReceiver = null; TextMessage message = null;


IBM Labs in Haifa



queueName = “Test Queue”;

/* * Create a JNDI InitialContext object if none exists yet. */ try {



}

/* * Look up connection factory and queue. If either does * not exist, exit. */ try {

queueConnectionFactory = (QueueConnectionFactory) jndiContext.lookup("QueueConnectionFactory");

queue = (Queue) jndiContext.lookup(queueName); } catch (NamingException e) {

System.out.println("JNDI lookup failed: " + e.toString()); System.exit(1);

}

IBM Labs in Haifa



try { queueConnection = queueConnectionFactory.createQueueConnection(); queueSession = queueConnection.createQueueSession(false,

Session.AUTO_ACKNOWLEDGE); queueReceiver = queueSession.createReceiver(queue); queueConnection.start();

while (true) { Message m = queueReceiver.receive(1); if (m != null) {

if (m instanceof TextMessage) { message = (TextMessage) m; System.out.println("Reading message: " +

message.getText()); }

} catch (JMSException e) {


IBM Labs in Haifa


JMS example: Pub/Sub Publisher (1/3)


public class SimpleTopicPublisher{public static void main(String[] args) {

String topicName = null; Context jndiContext = null; TopicConnectionFactory topicConnectionFactory = null; TopicConnection topicConnection = null; TopicSession topicSession = null; Topic topic = null; TopicPublisher topicPublisher = null; TextMessage message = null; final int NUM_MSGS; final String MSG_TEXT = new String("Here is a message");


IBM Labs in Haifa



topicName = “Test Topic”;/* * Create a JNDI InitialContext */ try {



}

/* * Look up connection factory and topic. If either does * not exist, exit. */try {

topicConnectionFactory = (TopicConnectionFactory) jndiContext.lookup("TopicConnectionFactory");

topic = (Topic) jndiContext.lookup(topicName); } catch (NamingException e) {

System.out.println("JNDI lookup failed: " + e.toString()); System.exit(1); }

IBM Labs in Haifa



try { topicConnection =

topicConnectionFactory.createTopicConnection(user, psswd); topicSession = topicConnection.createTopicSession(false,

Session.AUTO_ACKNOWLEDGE);

topicPublisher = topicSession.createPublisher(topic);

message = topicSession.createTextMessage(); for (int i = 0; i < NUM_MSGS; i++) {

message.setText(MSG_TEXT + " " + (i + 1)); System.out.println("Publishing message: " +

message.getText()); topicPublisher.publish(message);

} } catch (JMSException e) {


IBM Labs in Haifa


JMS example: Pub/Sub Subscriber (1/4)


public class SimpleTopicSubscriber{public static void main(String[] args) {

String topicName = null; Context jndiContext = null; TopicConnectionFactory topicConnectionFactory = null; TopicConnection topicConnection = null; TopicSession topicSession = null; Topic topic = null; TopicSubscriber topicSubscriber = null; TextMessage message = null; final int NUM_MSGS; final String MSG_TEXT = new String("Here is a message");


IBM Labs in Haifa



topicName = “Test Topic”;/* * Create a JNDI InitialContext */ try {



}

/* * Look up connection factory and topic. If either does * not exist, exit. */try {

topicConnectionFactory = (TopicConnectionFactory) jndiContext.lookup("TopicConnectionFactory");

topic = (Topic) jndiContext.lookup(topicName); } catch (NamingException e) {

System.out.println("JNDI lookup failed: " + e.toString()); System.exit(1); }

IBM Labs in Haifa



try { topicConnection =

topicConnectionFactory.createTopicConnection(user, psswd); topicSession = topicConnection.createTopicSession(false,

Session.AUTO_ACKNOWLEDGE); topicSubscriber = topicSession.createSubscriber(topic);

topicListener = new TextListener(); topicSubscriber.setMessageListener(topicListener);

topicConnection.start();

System.out.println("To end program, enter Q or q, " + "then <return>");

//Read user input, exit when Q/q entered

IBM Labs in Haifa



import javax.jms.*;

public class TextListener implements MessageListener {

public void onMessage(Message message) { TextMessage msg = null; try {

if (message instanceof TextMessage) { msg = (TextMessage) message; System.out.println("Reading message: " +

msg.getText()); } else { System.out.println("Message of wrong type: " +

message.getClass().getName()); }

} catch (JMSException e) {

System.out.println("JMSException in onMessage(): " + e.toString());

}

IBM Labs in Haifa


JMS Application Anatomy

A Connection Factory is the object a client uses to create a connection with a provider. A connection factory encapsulates a set of connection configuration parameters that has been defined by an administrator.

A Session is a single-threaded context for producing and consuming messages. You use sessions to create message producers, message consumers, and messages.

IBM Labs in Haifa


JMS Application Anatomy

JNDIConnectionFactories

Destinations

JMS Client

ConnectionFactory

Connection

Session

Session

Message

Server

IBM Labs in Haifa


JNDI

import javax.naming.*;

Properties env = new Properties();// Specify the vendor-specific JDNI propertiesjndiContext = new InitialContext(env); ….topicConnectionFactory = (TopicConnectionFactory)

jndiContext.lookup("TopicConnectionFactory"); topic = (Topic) jndiContext.lookup(topicName);

JNDI – Java Naming and Directory InterfaceKind of “remote hashtable” – given a key (String), returns the value (Object)

JMS “Adminsitered objects”:ConnectionFactory : message server address, clustering, transport configuration, security Destination (Queue and Topic): data channel configuration, naming

- are best maintained administratively rather than programmatically. The technology underlying these objects is likely to be very different from one implementation of the JMS API to another. Therefore, the management of these objects belongs with other administrative tasks that vary from provider to provider.

IBM Labs in Haifa


JNDI

Properties env = new Properties();// Specify the vendor-specific JDNI propertiesenv.put(Context.SECURITY_PRINCIPAL,”guest”);env.put(Context.INITIAL_CONTEXT_FACTORY, ”com.sun.jndi.ldap.LdapCtxFactory”);env.put(Context.PROVIDER_URL, “ldap://localhost:389/o=acme.com”);jndiContext = new InitialContext(env);

Alternatively, read JNDI environment properties from “jndi.properties” file.

IBM Labs in Haifa


JNDI Concepts

Names “Test Topic” (JMS topic) “www.ibm.com” (DNS address) “/usr/local/java/bin/javac” (File name)

BindingThe association of a name with an object is called a binding. For example, a file name is bound to a file.

ReferenceCompact object representation, with information about how to access the object

ContextA context is a set of name-to-object bindings, with an associated naming convention.E.g. Unix naming convention, “/abc/def”

Directory Attributes: Additional information on an object Directory service: creating, adding, removing, and modifying the attributes Search and Search filters

IBM Labs in Haifa


JNDI Architecture

IBM Labs in Haifa


JMS Message: Headers

JMS Message: Headers + Properties + Payload

Headers: JMSDestination JMSDeliveryMode JMSExpiration JMSPriority JMSMessageID : JMS provider JMSTimestamp: JMS provider JMSCorrelationID JMSReplyTo JMSRedelivered : JMS provider JMSType

IBM Labs in Haifa


JMS Message: Properties and Types

Properties message.setStringProperty(“Username”,”John Doe”);

Message Selectors Can use both Property and Header fields TopicSubscriber sub =

session.createSubscriber(chatTopic,”Username != ‘William’);

Message Types TextMessage A java.lang.String (for example, the contents of an eXtended Markup Language file)

MapMessage A set of name-value pairs, where names are String objects and values are primitive types in the Java programming language. The entries can be accessed sequentially by enumerator or randomly by name. The order of the entries is undefined.

BytesMessage A stream of uninterpreted bytes. This message type is for literally encoding a body to match an existing message format.

StreamMessage A stream of primitive values in the Java programming language. It is filled and read sequentially.

ObjectMessage A Serializable object in the Java programming language Message Nothing. Composed of header fields and properties only. No body.

IBM Labs in Haifa


Assured Delivery: Message Acknowledgements

AutoAcknowledgetopicSession = topicConnection.createTopicSession(false,

Session.AUTO_ACKNOWLEDGE);

Implicitly after onMessage return

ClientAcknowledge topicSession = topicConnection.createTopicSession(false,

Session.CLIENT_ACKNOWLEDGE);

Inside onMessage() – for speedier feedback On message group – message batch consumption in “all or

nothing” fashion

IBM Labs in Haifa


Assured Delivery: Durable Subscription

topicSubscriber = topicSession.createDurableSubscriber(topic,”Some name”);

IBM Labs in Haifa


Assured Delivery: Persistence

“Store-and-Forward” Remove upon Ack or Expiration

ProducerMessage

ServerConsumer

Storage

Ack

IBM Labs in Haifa


Local transactions

Producer – Provider Provider – Consumer

IBM Labs in Haifa


Bits & pieces

Temporary topics Temporary queues

Use in JMSReplyTo field Queue browsing

Any number of clients can connect to queueA message can be consumed by one only

“Pull” subscription.receive() instead of MessageListener

Dead Message Queue

IBM Labs in Haifa


Enterprise Application Integration

JMS

Server

Vendor A

JMS

Server

Vendor B

JMS

Client

JMS

Client

JMS

ClientJMS

Client

JMS

Client

JMS

Client

Legacy

System

JMS

Client

JMS

Client

Internet (http)

Gateway

E-Mail

gateway

IBM Labs in Haifa


JDBC

Uniform Java API to access any DB typeSQL wrapper

Install database driver Code snippets:

Connection con = DriverManager.getConnection(url, "myLogin", "myPassword");

String createTableCoffees = "CREATE TABLE COFFEES " + "(COF_NAME VARCHAR(32), SUP_ID INTEGER, PRICE FLOAT, " + "SALES INTEGER, TOTAL INTEGER)";

Statement stmt = con.createStatement(); stmt.executeUpdate(createTableCoffees);

stmt.executeUpdate("INSERT INTO COFFEES " + "VALUES ('French_Roast', 49, 8.99, 0, 0)");

ResultSet rs = stmt.executeQuery( "SELECT COF_NAME, PRICE FROM COFFEES"); while (rs.next()) {

String s = rs.getString("COF_NAME"); float n = rs.getFloat("PRICE"); System.out.println(s + " " + n);

}

IBM Labs in Haifa


Summary

Java Message Service (JMS) Messaging vs Traditional networking: Asynchronous, decoupled Publish/Subscribe, Point-to-Point messaging Architecture

Centralized Multicast Hybrid

Samples Assured delivery

Durable subscription Persistent publishing Acknowledged delivery

Enterprise Application Integration, Message-Oriented Middleware

JNDI Administered object management; Naming and Directory Services.

JDBC SQL wrapper; Database access

gidon gershinsky

Documents