Java Messaging Service

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D Copyright 2004-2008 Dan McCreary & Associates 1

Java Messaging Service (JMS)and Enterprise Messaging Strategy

Author: Dan McCreary

Date: 7/20/2004

Version: 0.1

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Objectives

• Understand strategies for computer-to-computer messaging

• Understand how vendors attempt to lock-in customers using proprietary communication APIs

• Understand why the Java Messaging Service (JMS) is becoming the de-facto vendor-neutral messaging interface between J2EE systems and how JMS helps avoid vendor lock-in

• Understand the differences between messaging systems

• Understand how messaging systems interoperate

• Understand how JMS fits in with other EAI architectures such as Web Services, SOA, ESB, Multi-tier architectures, J2EE Architecture, JCA, Microsoft BizTalk, RosettaNet

• Understand how future systems will interoperate

• Review references

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Messaging Strategy Overview

1. Support cost effective reliable messaging between state law enforcement agencies

2. Allow messages to have guaranteed delivery and be fully encrypted

3. Avoid vendor-specific APIs

4. Integrate with search and workflow

5. Be flexible for future standards

6. Make it easy for developers to use

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Vendor Lock-In

• Definition: When you spend a lot of time and money building your products around a specific vendor's solution.

• Vendor lock-in prevents you from moving your application to another vendor or an open-source solution

– Vendor lock-in is Bad

– Portability between vendors is Good• Successful Enterprise Architecture Strategies attempt

to minimize dependencies on any product due to:– Excessive licensing fees

– Excessive support fees

– Vendor support for a specific product

– Vendor stability

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Application Portability

• To promote portability and prevent vendor lock-in, whenever there is a choice between a vendor-neutral-industry-standard service interface and a vendor specific interface, always use the vendor-neutral standard unless you have a BUSINESS REASON to use the vendor specific interface

Application

Service

VendorNeutralService

Interface

VendorSpecificService

Interface

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What is A Message?• A communication between two things

(people, computers)

• Typical questions:– Who was the message from?

– What is the destination?

– Was the message actually received by the recipient?

– Was it understood? (what restaurant?, 8am or 8pm?)

– Should it be acknowledged?

– Could it have been tampered with in transit?

– Who really sent it?

Joe,

Lets meet for lunch atthe restaurant at 8.

- John

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Definition

Messaging: a method of communication between software components or applications– E-mail is also messaging but it is person to

person– In this tutorial, messaging is computer to

computer

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Messaging System

• A Messaging System is a peer-to-peer facility to allow any number computer applications to communicate with each other

• A messaging application can send messages to, and receive messages from, any other application

• Each client connects to a messaging interface that provides facilities for creating, sending, receiving, and reading messages.

Application

Interface

Application

Interface

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Messaging Clients

• A Messaging Client is a system that handles the communication between the application interface and the physical network

• A client can be either an open-source product or a commercial product

• Clients deal with issues such as how to send a message over an unreliable network

Application

Interface

Application

Interface

Client Client

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Store and Forward

• Messaging clients deal with issues such as how to send a message over an unreliable network with guaranteed security once-and only-once-delivery so that messages can be part of reliable distributed transactions (ACID)

Application

Interface

Application

Interface

Client Client

MessageServer

Store &Forward

MessageServer

Store &Forward

Unreliable Network

Unreliable Network

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Java Transaction API

• Java Transactions are handled by the Java Transaction API (JTA)

• The JTA makes it easy for Java programmers to do complex transactions involving data on multiple J2EE systems located over a wide area network (WAN)

• JTA depends on Messages Beans (MBean) and therefore JMS

• JTA makes ACID transactions possible

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ACID Test

• Atomicity – all or nothing – a transaction either completely succeeds or it completely fails – nothing in between

• Consistency – meet constraints of endpoints such as non-duplicate ID numbers

• Isolation – each transaction has a consistent view of the world

• Durability – once committed the transaction will endure regardless of single component failure

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A Wire Protocol

• A wire protocol is an agreed upon standard between two systems (potentially built with different technologies) that defines how they will communicate with each other

Format of messages "on the wire"

Examples: HTTP (web), SMTP (mail), SNMP (monitoring) and SOAP

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System Coupling

• TIGHT: Systems that are very rigid in their requirements

• System 2 MUST respond to a message before System 1 can proceed to the next activity

• LOOSE: Where programmers just send a message and can be assure the infrastructure will do whatever it needs to do send the message

System 1 System 2

System 1 System 2

Tight Coupling

Loose Coupling

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Tightly Coupled Communications

• Sender needs a remote service and calls a remote procedure call• The sending process “Stops” and waits for a reply• Synchronous messaging – don’t proceed till we are synchronized up• The sender will “freeze” if the network is down or the sender will have to

manually keep trying till the remote system is up and it gets a response• Remote procedure call (RPC), Java Remote Method Invocation (RMI)

System 1

Unreliable Network

Unreliable Network

System 2

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Loosely Coupled Communications

• Programmers just “fire and forget”• There is no “blocking” of sender’s process• System 1 just gets a reply message when the data request has been received• System can transmit messages to remote systems even when the remote system is down or

the network has failed. Messages wait patiently in the queue till the network is back up.• System administrators can monitor the message queues and be notified of congestions• High priority messages can take precedence over large, batch transfers

System 1

Unreliable Network

Unreliable Network

System 2

MessageQueue

MessageQueue

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Application Program Interface (API)• A formal set of interfaces definitions used by programmers

• Usually a specified in SPECIFIC language such as Java or C

• Java Messaging Service (JMS) is an API

• JMS was designed to be a wrapper API around existing messaging systems

J2EEApplication(JMS Client)

JMS Provider

JMS API

J2EEApplication(JMS Client)

JMS Provider

JMS API

Messaging System

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APIs Promote Portability

• Applications DO NOT call an vendor interface directly

• Applications call the industry standard and let the transport mechanism move the data

Sun Certified J2EE 1.3+Application Server

JMS Interface

Application

Transport Mechanism

Vendor Interface

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JMS is part of J2EE

• In order to be a Sun-certified J2EE 1.3+ compliant, the application server MUST support the JMS interface (1.2 was only recommended)

• Any object can use the JMS API

• JMS is THE default application server messaging interface

Sun Certified J2EE 1.3+Application Server

JMS Interface

Transport Mechanism

Application

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JMS Details

• JMS is a Messaging API Specification

• Published and maintained by Sun Microsystems

• First published in August 1998.

• Latest version is Version 1.0.2b

• See http://java.sun.com/products/jms/

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Goals of JMS

• Minimizes the set of concepts a programmer must learn to use messaging products (programmer friendly)

• Provides enough features to support sophisticated messaging applications

• Maximize the portability of JMS applications across JMS providers in the same messaging domain

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Benefits of JMS

• Simplifies enterprise development

• Allows loosely coupled systems (systems that don't block each other)

• Provides reliable messaging over an unreliable network

• Promotes secure messaging between systems

• Messages between JMS systems can be encrypted

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Vendors Passing JMS Compatibility Tests

Part of the J2EE SDK version 1.3. J2EE

Must licensees Sun technology to be certified

• BEA Systems, Inc.

• Hewlett-Packard

• IBM

• JBoss

• Sun

• Macromedia

• Oracle Corporation

• Pramati

• SeeBeyond

• SilverStream Software, Inc. (Novell)

• Sonic Software

• SpiritSoft, Inc.

• Talarian Corp.

• TIBCO Software, Inc.

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JMS is NOT a Wire Protocol

• The JMS API is promoted as a technology for providing high-quality reliable communication between components within an enterprise, but not for business-to-business (B2B) communication between enterprises over the Internet

• JMS is an insulator for proprietary messaging APIs

• JMS is not a router to router specification

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JBoss and JBossMQ

• JBoss has an implementation of the JMS interface

• JBoss has an implementation of the JMS transport service

• JMS isolates the application from dependencies of specific transport systems

JBoss

JMS Interface

JBossMQ

Application

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JBossMQ

• Initially released as spyderMQ

• "clean room" implementation– programmers given an interface specification

but have never seen similar systems – very low risk of copyright infringement

• First release April 2000

• Active users migrated from standalone spyderMQ to JBossMQ

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JBossMQ

• Full implementation of JMS specification including:– Point-to-point– Publish-subscribe– Durable subscribers– JMS Application Server Facilities– Global work units can be coordinated by

transaction manager

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When to Use a JMS Interface?

• The provider wants the components not to depend on information about other components' interfaces, so that components can be easily replaced

• The provider wants the application to run whether or not all components are up and running simultaneously

• The application business model allows a component to send information to another and to continue to operate without receiving an immediate response

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ISO Seven Layer Reference Model

• Seven layers of "Abstraction" that allows applications to communicate with each other

• Lowest level is the physical wire

• Internet Protocol is in the middle

Physical

Data Link

Network

Transport

Session

Presentation

Application

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Communication Occurs at the Lowest Level

Physical

Data Link

Network

Transport

Session

Presentation

Application

Physical

Data Link

Network

Transport

Session

Presentation

Application

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What is a "Common Language"?

Sound

Phonemes

Words

Sentences

Conversation

Problem Solving

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Computer to Computer

Internet

XML

XML Tags

XML Schemas

Interface Definitions

Service Level Agreements

WSDL

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Publish/Subscribe Securely

Subscriber 1

Publisher 1

Criminal Justice Information Bus

Publisher 2 Publisher 3

Subscriber 2 Subscriber 3

Authentication

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3 EAI Architectures

Presentation

Database

MethodMethod

Presentation

Database

Presentation

Method

Data

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Evolution of EAI

Share process

Share read-write data

Share read-onlydata

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Why Share Process?

• Sharing data requires you to know who has the right data: the synchronization problem and the metadata problem.

• Sharing process allows you to avoid rewriting code.

• Quality of data is dependant on the process that validate it.

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Challenges: Share Process and Data

• Allow any application developer to easily allow both user and programmatic access to application services.

• Often requires developers to re-conceptualize their applications as a series of published services: e.g. Web Service

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EAI is Expensive

• Up to 30% of costs of installing enterprise applications are related to integration.– Gartner Group

Initial LicenseCosts

Integration Costs

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Asynchronous Messaging

• Ways that objects communicate

• A service of the underlying operating system

• Allows programmers to “fire and forget”

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Message Brokers

Use of a broker will reduce these integration costs by one-third. During maintenance, when a single change to an application can have a rippling effect on several to several dozen interfaces, use of a broker can reduce costs by two-thirds.“

- Gartner Group

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Message Queuing

• Message Oriented Middleware – Product Classification

• IBM MQSeries - Product

• Microsoft MSMQ - Product

• Java 2 Enterprise Edition (J2EE 1.4)- J2EE – Application Server Standard

• Java Messaging Service - JMS

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Messaging Benefits

• Messaging infrastructure guarantees reliable delivery of a message

• Once and only once delivery

• Messages can have different priority

• Transactional control

• Transactions can be grouped together

• Support of “undo” – reversible operations

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Similar to E-mail

Header:Header:To: From: Subject:

Priority: Urgent

To: From: Subject:Priority: Urgent

BodyBody

Recipientse-MailServer

OutgoingMail

Server

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When we send e-mail…

• Sender sends a message to the outgoing e-mail server using a standard format ( e.g. Simple Mail Transfer Protocol)

• Message is routed to receiver’s e-mail server

• Message stored in e-mail server till the receiver picks up the message

• Example of asynchronous processing

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Message Structure

HeaderHeader

PropertiesProperties

BodyBody

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Object to Object Messaging

HeaderHeader


BodyBody

MessageQueue

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Header

• Identify message• Destination• Routing Information• Priority• Timestamp• Reply to• Message type

HeaderHeader


BodyBody

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Properties

• Added by the application developer

• Application specific properties

• Key-value pairs– KEYWORD=VALUE

• Extensions for messaging systems

HeaderHeader


BodyBody

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Body

• Message body• Can contain arbitrary data

types– Text messages

– Map (key-value pairs)

– XML

– Serialized objects (Java)

– Binary data

– Empty

HeaderHeader


BodyBody

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Message Example

To: My Enterprise Service BusTo: My Enterprise Service Bus

TransactionNumber=12345TransactionNumber=12345

<?xml version="1.0"?><RequestedAction>Person Search</RequestedAction><Person> <PersonSurName>Jones</PersonSurName> <PersonGivenName>Sam</PersonGivenName> <PersonBirthDate>1980-12-31</PersonBirthDate></Person>

<?xml version="1.0"?><RequestedAction>Person Search</RequestedAction><Person> <PersonSurName>Jones</PersonSurName> <PersonGivenName>Sam</PersonGivenName> <PersonBirthDate>1980-12-31</PersonBirthDate></Person>

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JMS Modes

• One-to-one (aka Point-to-point)– Send a message to a JMS Queue

– One message reader

• One-to-Many (aka Publish-subscribe)– Send (publish) message to a JMS Topic

– Enables many readers (subscribers)

– Also enables many-to-many subscription

Queue

Message

Receiver

Sender

Topic

Message

Subscriber

Sender

Subscriber

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Required Header Types

• Automatic – automatically put in EVERY message by the system

• Developer-Assigned – required headers that must be set before a send()

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Automatic Header Information

• Destination – where to send the message (either a queue or a topic)

• DeliveryMode – reliable or not• MessageID – number that identifies the message• Timestamp – date and time that send() was called• Expiration – time to live in milliseconds – by

default is does not expire• Redelivered – not the first try• Priority – Should this message be expedited?

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Priority Messages

• The JMS API defines ten levels of priority value

• 0 as the lowest priority

• 9 as the highest

• 0-4 are gradations of normal priority and priorities

• 5-9 are gradations of expedited priority

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Developer Assigned

• ReplyTo – who should the receiver send a reply to

• CorrlationID – how this message is related to previous messages

• Type – The type of the payload – binary, text, XML etc.

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Multi-Tier Architecture

Presentation

Control

Process

Persistence

Database

Window Controller

Customer Order

Database Adapter

Customer

First Name:

Last Name:

Phone:

Save

Database

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J2EE Container Architecture

• J2EE allows developers to create "beans" that inherit common characteristics

• Everything inside a container can have a common set of characteristics

• Data, Communication, Security

Application Server

Container

Bean

Bean Bean

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J2EE Bean Types

• J2EE allows developers to create "beans" that inherit common characteristics

• Everything inside a container can have a common set of characteristics

• Data, Communication, Security

Application Server

Container

MessageBeanEntity

Bean

SessionBean

DBJMS Provider

User

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JCA: J2EE Connection Architecture

Application Server

Container

Connection PoolManager

TransactionManager

SecurityServicesManager

Application ComponentApplication Component

Container-ComponentContract

SystemContract Resource Adapter

Application Contract

EIS-specific Interface

Enterprise InformationSystem

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Bridges

• Bridges translate from one vendor system into another

• Example IBM-MQ to/from MSMQ

• Some loss of information when headers do not have precise mappings

• Allows interoperability

Vendor A Vendor B

Translation

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JMS and Web Services

• Web service are similar yet different from JMS

• Web services is vendor and language neutral (works with Microsoft, C#, VB etc.)

• Web service can have semantically clear published interfaces

• Web service are not inherently reliable and do not offer standards for retransmission

• Built on SOAP which is extensible

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SOAP is a wire protocol for exchanging messages

• Any XML tags can be added to SOAP header to tell the receiving system how to transmit the message

• Security can also be added

• Must agree on what tags to use

SOAP DocumentSOAP DocumentSOAP Header

SOAP Body

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Future WS-Reliable, WS-Secure

• New web-service standards to provide wire-protocol reliable and secure web services

• Emerging standards from IBM, Microsoft, TIBCO etc.

• Sun, Oracle have a similar standard WS-Reliability

• Wait for standards to shake out before adopting

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CriMNet Tiers

CriMNetServices

Servlets

XML/XSLT

MessageProcessing

RequestHandler

RulesProcessing

SessionManager

SessionController

Interactwith the

Database

AccessSecurity

Operations ConsoleŸ Monitoring,Ÿ Reporting,Ÿ Administration

Registry(Unique ID’s)

JSP w/Custom Tags

CriMNet websiteŸ Registration

RequestŸ Locater / Query

RequestŸ Web Site

.

.

.

Locator

CriMNetHelper

NaturalLanguageTranslator

CriMNetDatabase

Interface withLegacy systems

(e.g. local agencies)

ClientŸ Browser (SSL)Ÿ Custom App via

https

Logging

QueryServices

AssociationServices

Other CriMNet Hub

Point-to-Point

Publish

OperationalSystems

JMS Server

Admin

Messaging

Engines

Biometrics

Fax Server

DirectoryServices

Custom

Adaptor

Registry

Logging

Config

Profiles

Meta Data

Critical Data

Rules

Archiving

Services

Search Module

Registration

Tier

CriMNetCommunication

Tier

CriMNet Hub Server

HTTPS

From January 2000 Macro Group Logical Architecture

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BizTalk Architecture

BizTalk ServerBizTalk Server BizTalk ServerBizTalk Server

ApplicationApplication

AdapterAdapter

BizTalk DocBizTalk DocHeader

Body

BizTalk DocBizTalk DocHeader

Body

Transport EnvelopeTransport Envelope

BizTalk Message

InternetInternet

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BizTalk Constraints

• Protocols are proprietary to Microsoft

• XLang is only used by Microsoft

• All endpoints are MSMQ

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RosettaNet

• Agree on bottom six layers of OSI model

• Subdivide application layer into seven distinct layers

PhysicalData LinkNetwork

Presentation

Application

SessionTransport

Security

Transfer

Agent

Service

Process

Transaction

Action

Message Handling

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JMS and ESB

"An ESB can be a sensible first step toward a systematic Enterprise Nervous System because it provides the basic connectivity backbone. It can interoperate with a variety of disparate application servers simultaneously, smoothing over technical differences and also providing services for communication and integration.”

Roy SchulteVP and Research FellowGartner Research

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References

• Best high-level book for EAI architects using J2EE– J2EE Connector

Architecture and Enterprise Application Integration (by Sharma, Stearns and Ng)

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JMS Textbooks

1. Java Message Serviceby Richard Monson-Haefel and David ChappellGood explanation on how to use JMS for programmers

2. Java Message Service API Tutorial and Reference: Messaging for the J2EE Platform by Mark Hapner, Rich Burridge, Rahul Sharma, Joseph Fialli, Kim Haase

3. Enterprise JMS Programmingby Shaun Terry

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JBossMQ

• JBoss Administration and Developmentby Marc Fleury, Scott Stark

• Chapter 4 has an excellent chapter on JMS and JBossMQ

• Chapter 6 covers Transactions

• Chapter 7 covers Connector Architecture

• (book only covers JBoss up to 2.4.x)

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Thank You!

Please contact me for more information:• Enterprise Service Bus• Native XML Databases• Metadata Management• Metadata Registries• Service Oriented Architectures• Business Intelligence and Data Warehouse• Semantic Web

Dan McCreary, PresidentDan McCreary & Associates

Metadata Strategy [email protected]

(952) 931-9198

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Java Messaging Service

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