ja331 - unit jms and mdb

8/12/2019 Ja331 - Unit Jms and Mdb

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Java Message Service &

Message Driven Beans

JA 331 - SAP JavaOpen IntegrationTechnologies


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SAP AG 2004, JA 331 / Unit: JMS and MDB / 2

After completing this unit, you will be able to:

name the participants and explain the concepts of

the Java Message Service (JMS)

give examples where JMS can be used

describe the special features of Message Driven

Beans (MDBs)

implement general JMS applications and MDBs

using the SAP NetWeaver Developer Studio

explain the special JMS features in SAP NetWeaver

04

Java Message Service and Message Driven Beans:Unit Objectives


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JMS is adequate for coupling systems which have to

exchange data, but to not depend on the other

systems immediate reaction.

Scenario:

A company hasamong otherstwo systems. One

is located in a call center, one in the accounting

department.

The call center agents enter new complaints and

have the possibility to grant a financial

compensation to the customers. If they do so, thesystem they use will send a message to the

accounting system and they can proceed with their

workit does not matter to them when the

accounting guys will execute the request.

Java Message Service and Message Driven Beans:Business Scenario


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After completing this topic, you will be able to:

name the participants involved in the Java Message

Service (JMS)

explain the basic concepts of JMS

implement an application for sending a message

explain the transaction concept used for JMS

Java Message Service: Topic Objectives


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Asynchronous Messaging

Benefits:

Better performance: Avoid waiting for replies

Loosely coupling of systems

Connection of systems written in different languages

Message-OrientedMiddleware

System 1 System 2

Asynchronous messaging can be compared to e-mail

communication between people


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Java Message Service

The Java Message Service is a Message-Oriented Middleware

(MOM)and thus allows to decouple producers and consumers

of messages

The JMS API

defines a vendor independent access to variousMOM (JMS based) systems

is part of the J2EE platform

is defined within the javax.jmspackage



JMS Providers provide an implementationof the JMS API

Web Application Server

JMS Clients use the implementation and can be

Producers(send messages)

Consumers(receive messages)

JMS Providers & Clients



JMS Destinations

Queue Topic

Point-To-Point

One registered receiver per

message

Publish-Subscribe

Many receivers per message

possible

2 kinds of subscription

Non-durable

Durable

Durability by store-and-forward

messaging

FIFO

M i M d l



JMS Provider

Messaging ModelsPoint-to-Point / Publish-Subcribe

Queue

Sender QueueReceiver

Queue

23

145

1 2 3

1. Messages to be sent

2. Messages waiting in the Queue

3. Messages being consumed

Topic

2

Topic

Publisher

3

Topic

Subscriber 2

Topic

Subscriber 1

1a

1b


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Message Format

Header

Properties

Body

Administrative Information;

key-value-pairs

Additional Information;

key-value-pairs

A Message of one of the following types:StreamMessage

MapMessage

TextMessageObjectMessage

BytesMessage

[Message( has no body)]

Some may be

disabled to

improve

performance

S di



InitialContext iCtx = new InitialContext();

QueueConnectionFactory queueConnectionFactory =

(QueueConnectionFactory)iCtx.lookup("java:comp/env/jms/QConnFactory");

QueueConnection queueConnection =

queueConnectionFactory.createQueueConnection();

QueueSession queueSession =

queueConnection.createQueueSession(true, 0);

//true -> session is transacted; 0 -> acknowledgement

not specified

Queue queue =

(Queue)iCtx.lookup("java:comp/env/jms/myQueue");

QueueSender queueSender =

queueSession.createSender(queue);

Sending a messageSource code / 1

Queue

ConnectionFactory

Queue

Session

Queue

Sender

Queue

Connection

Queue

S di



Message message = queueSession.createMessage();

message.setStringProperty("name", "value");

//...

queueSender.send(message);

Sending a messageSource code / 2

Queue

Connection

Factory

Queue

Session

Queue

Sender

Queue

Connection

Queue

1

2

1

2

S di



Sending a messageLogical names and Mapping

QueueConnectionFactory queueConnectionFactory =

(QueueConnectionFactory)

initialContext.lookup("java:comp/env/jms/QConnFactory");

jms/QConnFactory

...

jms/QConnFactory

QueueConnectionFactory

Source Code

Standard

deployment

descriptor

Vendordeployment

descriptor

1

2



Sessionsmay be specified as transacted.

Finishing a transaction automatically starts the next.

call commit()/ rollback()on your session

Receiving

App

JMS Provider

Transactions

Sending

App

Session A Session B

4 3

Transaction B1

2 1

Transaction A1

6 5



Acknowledgement

If a session is not transacted, there are three ways to realize theacknowledgement:

AUTO_ACKNOWLEDGEthe session acknowledges the message receipt

clients have to be prepared to receive the last messagemore than once

DUPS_OK_ACKNOWLEDGElazy acknowledgement; may result in duplicate messages

clients have to be prepared to receive multiplemessages more than once

CLIENT_ACKNOWLEDGE

the client acknowledges; the acknowledgement of onemessage automatically acknowledges all other messages

Flag: JMSRedelivered(message header) for resent messages



You should now be able to:

name the participants involved in the Java Message

Service (JMS)

explain the basic concepts of JMS

implement an application for sending a message

explain the transaction concept used for JMS

Java Message Service: Topic Summary


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state the differences between Message Driven Beans

(MDBs) and other Enterprise Java Beans

explain how messages are passed to MDBs

implement an MDB

Message Driven Beans: Topic Objectives


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Enterprise Java Beans Overview

Session

Beans

Entity

Beans

EJB

Stateless Statefull ContainerManaged

Persistence

BeanManaged

Persistence

Asynchronous

Communication

Message Driven

Beans

Synchronous Communication


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Message Driven Beans

came new with EJB 2.0

are handled by the EJB Container, which acts as a JMS ClientMDBs can consume messages (and optionally produce

them)

will be assigned to one Topic or Queue

are server-side components(like other EJBs) and consist of

the bean class

two deployment descriptors

nointerfaces (home, remote)

MDBs are accessed by sending messages to the accordingQueue or Topic

are stateless


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The Dual Nature of MDBs

EnterpriseBean

ExampleMDB

MessageDrivenBean

MessageListener

The business logic is put

into the onMessage() method.

javax.ejb.MessageDrivenBean

by this MDBs inherit the

methods the container needs to

handle them like other EJBs

javax.jms.MessageListener

provide an asynchronous

receipt of JMS messages

T ti


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Transactions

MDBs do not use the usual JMS transaction model; they can make

use of distributed transactions

container-managed transaction demarcation

The onMessage()method gets one the following attributes

Required: The message receiptand theonMessage()methodrun within the same, new transaction.

NotSupported: The onMessage()method runs without a

transaction.

bean-managed transaction demarcation

The onMessage()method starts and commits transactions

explicit.

P ll l P i


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Parallel Processing

The EJB Container handles several instances of one MDB at one

time server-side concurrentprocessing

All instances are equivalent

Each MDB instance runs within its own thread.

There is no guarantee that messages are delivered

in exact the same order as they are sent.

JMS ProviderEJB

Container

MDB

Instance 1Thread A

MDB

Instance 2Thread B

MDB

Instance 3Thread C

MDB

Lif l


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Lifecycle

does not

exist

method-ready

pool

ejbRemove()//create a new instance

setMessageDrivenContext()

ejbCreate()

onMessage()

called before

deletion

invoked on

message

receipt

called after

creation

Deployment Descriptors


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Deployment Descriptorsejb-jar.xml / 1

MDBs are declared in the ejb-jar.xmlwithin the tag

EJB relateddata / Messaging relateddata

EJB name

bean class name

transaction demarcation type

environment entries used by the MDB

The JMS destination type the MDB listens to

EJB related

Messaging

related



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Deployment Descriptorsejb-jar.xml / 2

Name / class

Destination type

Environment



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Deployment Descriptorsejb-j2ee-engine.xml

Vendor specific descriptor

contains additional information JMS information

the concrete destination of the MDB

the concrete ConnectionFactory used

M D i B T i S


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state the differences between Message Driven Beans

(MDBs) and other Enterprise Java Beans

explain how messages are passed to MDBs

implement an MDB

Message Driven Beans: Topic Summary

JMS @ SAP NetWea er 04 Topic Objecti es


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state the special features regarding the Java

Message Service in SAP NetWeaver

create a Message Driven Bean with the SAP

NetWeaver Developer Studio

JMS @ SAP NetWeaver 04: Topic Objectives

Overview


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Overview

Full implementation of JMS 1.0.2b

Integrated in SAP NetWeavers Security concepts Accessing the central user store you can determine who

is allowed to administrate JMS objects.

For all destinations (Queues & Topics) it can be definedwho is allowed to send to or receive from them.

Failover Capability

JMS Connector

IDE Support

Failover capability


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Failover capability

Cluster

JMS

If the node with the JMS Service running on it crashes, another

node will host it.

Cluster

JMS

Cluster

JMS

JMS Connector / 1


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JMS Connector / 1

Through the JMS Connector it gets transparent for the application

which JMS Provider is used.

JMS App JMS App JMS App

JMS Provider

JMS ConnectorXML

JMS Connector / 2


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JMS Connector / 2

jms/QConnFactory



...

jmsfactory/default/QueueConnectionFactory

Vendor

deployment

descriptor

JMS Connectordeployment

descriptor

JMS Provider /

JNDI

[Source code / standard deployment descriptor]

1

2

IDE Support


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ppCreating a new MDB / 1

IDE Support


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ppCreating a new MDB / 2

Deployment

descriptor

MDB classBusiness Logic

IDE Support


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ppBidirectional Editing

JMS @ SAP NetWeaver 04: Topic Summary


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state the special features regarding the Java

Message Service in SAP NetWeaver

create a Message Driven Bean with the SAP

NetWeaver Developer Studio

JMS @ SAP NetWeaver 04: Topic Summary

Java Message Service and Message Driven Beans:


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name the participants and explain the concepts of

the Java Message Service (JMS)

give examples where JMS can be used

describe the special features of Message Driven

Beans (MDBs)

implement general JMS applications and MDBs

using the SAP NetWeaver Developer Studio

explain the special JMS features in SAP NetWeaver04

Unit Summary

ja331 - unit jms and mdb

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