deploying a stateless ejb

8/14/2019 Deploying a Stateless EJB

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Developing a Stateless Session

Enterprise Java Bean


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Copyright 2000 Sun Microsystems, Inc., All rights reserved.

How to develop and deploy a statelesssession bean by example:

What is a stateless session bean When to use session beans Steps for implementing a stateless session

bean Overview of EJB APIs Example Stateless session bean

implementation Assembling an deploying the example session

bean Writing and running the client of the example

session bean

Session Bean Tutorial Agenda:


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Session beans are typically usedfor business process or controllogic that spans multiple entitybeans

Entity Bean Entity Bean

What Are Session Beans?

entity entity entity

session

A session bean is implemented to perform a sequence of tasks within the

context of a transaction. For example, a session bean can execute a process or

a transaction that accesses a database to display certain information to the

client.


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What Is a Session Bean?

Is relatively short- lived (life typically isthat of its client).

Is removed when the EJB servercrashes.

Does not represent data in database, butcan access it.

Executes on behalf of a single client.

Can be transaction aware.


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When to Use Session Beans?

Use Session beans to model process orcontrol objects specific to a particularclient.

To model workflow, processes or tasks,manage activities (make reservation,purchase...).

To Coordinate processes between entitybeans, control interactions of beans.

To put business application logic on the

Server Side.


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Session Beans Represent a

business process

One instance perclient

Short-lived: Life ofclient is life of bean

Transient Doesnt survive

server crashes May be

transactional

Entity BeansRepresent business data

Shared instance formultiple clients

Long-lived: as long asdata in database

Persistent

Survive server crashesAlways Transactional

Session vs. Entity Beans

3 major design patterns for distributed objects multi-tier systems:

EJB stateless session bean: stateless server object: object which provides

responses to requests without storing information between requests (like http).

Can be re-used on different client after method call finished.

EJB stateful session bean: session oriented object: session is acting as agentfor the client, keeping state information until session is finished , 1 per client

until session is finished.

EJB entity bean: persistent object: wraps "object data" stored in a database

and provides operations to manipulate this data. shared among multiple clients

concurrently.


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2 Types of Session Beans

Stateless: execute a request and returna result without saving any client specificstate information.

transient

temporary piece of business logic neededby a specific client for a limited timespan

Stateful: maintains client specificstate.

State instance data

Stateless session beans model business processes that can be completed in a

one method call.

Stateless session beans do not maintain their state across method calls.

Typically, you use stateless beans when the entire task can be performed

within a single method call.

Any instance of a stateless session bean can be used at any time by any client.


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Stateless Session Beans

oStateless beans:o Do not retain client information

from one method invocation to thenext.

o Client passes any needed informationas parameters to the businessmethods.

oUsed mainly to provide a pool of beans tohandle frequent but brief requests.

oThe EJB server transparently reusesinstances of the bean to servicedifferent clients.

Stateless Session Beans

Stateless session beans are designed strictly to provide server-side behavior.

They are anonymous in that they contain no user-specific data. In fact, the

EJB architecture provides ways for a single stateless session bean to serve the

needs of many clients.

This means that all stateless session bean instances are equivalent when they

are not involved in serving a client-invoked method. The term stateless means

that it does not have any state information for a specific client. However,

stateless session beans can have non-client specific state, for example, an open

database connection.

A stateless session Bean maintains no state across methods and transactions

-the EJB server transparently reuses instances of the Bean to service

different clients at the per-method level (access to the session bean is

serialized and is 1 client per session bean per method.

-Pool of session beans < # clients because they can be reused


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Stateless vs Stateful

Cart items

request with parametersneeded for processing


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Stateless May Use FewerResources:

oNumber of Stateless Session Beansneeded < Number of Clients:

o Can be recycled.

o Number of instances to create isminimized.

o Shorter life (no client session) optimizesresource usage.

o Improved performance due to fewerconnections across the network.

oBut may require the client to maintainstate information on the client side whichcan mean more complex client code.

Note: The difference in use of resources for stateless and stateful is application

server specific.


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When to use Stateless SessionBeans?

The following guidelines can be used formodeling stateless session components:

Reusable service objects

May provide high performance

Not tied up to one client after methodcompletes.

Need to operate on multiple rows at atime (read- only view)

Provides procedural view of data,(Entity Bean provides object view ofdata.)

5.4.2.1 Uses of Stateless Session Beans

A Bean Provider can use the following session bean characteristics as guidelines when deciding whether

to model a business object as a stateless session bean:

Modeling reusable service objects

A business object that provides some generic service to all its clients can be modeled as stateless session

beans. Such an object does not need to maintain any client specific state information, so the same bean

instance can be reused to service other clients. For example, it would be appropriate to model a business

object that validates an employee ID against a database as a state-less service.

Providing high performance

A stateless session bean can be very efficient as it requires fewer system resources by the virtue of being

not tied to one client. Since stateless session beans minimize the resources needed to support a large

number of clients, depending on the implementation of the EJB server, applications that use this approach

may scale better than those using stateful session beans. However, this benefit may be offset by the

increased complexity of the client application that uses the stateless session beans because the client has

to perform the state management functions.

Operating on multiple rows at a time

A business object that manipulates multiple rows in a database and represents a shared view of the data

is an ideal stateless session bean. An example of a such business object would be a catalog object that

presents a list of various products and categories. Since all users would be interested in such information,

the stateless session bean that represents it could easily be shared.

Providing procedural view of data

In a procedural view of data, methods of the business object do not operate on instance variables. Instead

they behave like calls in a procedural language. The method caller provides all the input and the method

returns all output to the caller. If a business object exhibits such functionality then it should be modeled

as a stateless session bean.

Example: A Catalog Bean

The sample application uses a stateless session beans to model a catalog object. A catalog object provides

browsing and searching services to its clients. Both of the primary functions of the catalog, browsing and

searching, are generic services that are not tied to any particular client. Also, the catalog object operates

on multiple rows in the database at the same time and provides a shared view of the data.


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Implementing a Session Bean

In this session we will discuss an examplestateless session bean, we will discussstateful in a later session.

As an example we will use the ATMsession bean from the bank accounttransfer scenario.


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Transfer

Money

Use Case: ATM customer transfers money from checking

to savings account

Example Scenario: Use Case

Customer


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ATM Account

accesses

Checking

Account

Savings

Account

transfer() withdraw()

deposit()

0* 0*

Example Scenario: Classes

balance


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: CustomerATM saving

accountcheckingaccount

1: transfer()

2: debit()

Example Scenario: SequenceDiagram

3: credit())


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Account

Entity Bean

Account

Entity Bean

ATM

Session beanClient

Transfer

debit

credit

account1

account2

Example Scenario: EJB


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Session Bean Implementation

1. Create the remote interface for thebean.

2. Create the beans home interface.

3. Create the beans implementationclass.

4. Compile the remote interface, homeinterface, and implementation class.

5. Create a deployment descriptor.

6. Package in an ejb- jar file.7. Deploy the enterprise application.

What the ATM session Bean provider is responsible for:

Define the session Beans remote interface (Atm). The remote interface

defines the business methods callable by a client. The remote interface must

extend the javax.ejb.EJBObject interface, and follow the standard rules for a

RMI-IIOP remote interface. The remote interface must be defined as public.

Write the business logic in the session Bean class (AtmBean). The

enterprise Bean must implement the javax.ejb.SessionBean interface, and

define the ejbCreate(...) methods invoked at an EJB object creation.

Define a home interface (AtmHome) for the enterprise Bean. The home

interface must be defined as public, extend the javax.ejb.EJBHome interface,

and follow the standard rules for RMI-IIOP remote interfaces.

Define a deployment descriptor specifying any declarative metadata that the

session Bean provider wishes to pass with the Bean to the next stage of the

development/deployment work-flow.


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EJB API Review

java.RMI.Remote

java.io.serializable

EJBHome

EJBObject

JDK

javax.ejb

Beanprovider

xxxContainerprovider

EnterpriseBean

SessionBean

AtmHome

Atm

AtmBean

xxxatmEJBHome

xxxatmEJBObject

xxxAtmBean

The tools provided by xxx Corporation are responsible for the following:

Generate the class (xxxRemoteAtm) that implements the session beans

remote interface. The tools also generate the classes that implement the

communication protocol specific artifacts for the remote interface.

Generate the implementation of the session Bean class suitable for the xxxcontainer (xxxAtmBean). xxxAtmBean includes the business logic from the

AtmBean class mixed with the services defined in the xxxBean class. xxx tools

can use inheritance, delegation, and code generation to achieve a mix-in of

the two classes.

Generate the class (xxxAtmHome) that implements the session beans

home interface.

Generate the class (xxxAtmMetaData) that implements the

javax.ejb.EJBMetaData interface for the Atm Bean.


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javax. EJB Client Interfaces

java.RMI.Remote

EJBHome

remove()getEJBMetaData()getHomeHandle()

EJBObject

getEJBHome()

remove()getHandle()isIdentical()

extends

The EJBHome interface is extended by all enterprise Bean's home interfaces. An enterprise Bean's home interface

defines the methods that allow a client to create, find, and remove EJB objects. Each enterprise Bean has a home

interface. The home interface must extend the javax.ejb.EJBHome interface, and define the enterprise Bean type

specific create and finder methods (session Beans do not have finders). The home interface is defined by the enterprise

Bean provider and implemented by the enterprise Bean container. Method Summary:

EJBMetaData getEJBMetaData()

Obtain the EJBMetaData interface for the enterprise Bean.

HomeHandle getHomeHandle()

Obtain a handle for the home object.

Void remove(Handle handle)

Remove an EJB object identified by its handle.

Void remove(java.lang.Object primaryKey)

Remove an EJB object identified by its primary key.

The EJBObject interface is extended by all enterprise Bean's remote interface. An enterprise Bean's remote interface

provides the client's view of an EJB object. An enterprise Bean's remote interface defines the business methods

callable by a client. Each enterprise Bean has a remote interface. The remote interface must extend the

javax.ejb.EJBObject interface, and define the enterprise Bean specific business methods. The enterprise Bean's remote

interface is defined by the enterprise Bean provider and implemented by the enterprise Bean container. Method

Summary

EJBHome getEJBHome()

Obtain the enterprise Bean's home interface.

Handle getHandle()

Obtain a handle for the EJB object.

java.lang.Object getPrimaryKey()

Obtain the primary key of the EJB object.

Boolean isIdentical(EJBObject obj)

Test if a given EJB object is identical to the invoked EJB object.

void remove()

Remove the EJB object.


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javax. EJB Server Interfaces

java.io.serializable

EnterpriseBean

EntityBean

setEntityContext()unsetEntityContext

ejbRemove()ejbActivate()

ejbPassivate()

ejbLoad()ejbStore()

SessionBean

setSessionContext()ejbRemove()ejbActivate()

ejbPassivate()

The EnterpriseBean interface must be implemented by every enterprise Bean

class. It is a common super interface for the SessionBean and EntityBean

interfaces.

The SessionBean interface is implemented by every session enterprise Bean

class. The container uses the

SessionBean methods to notify the enterprise Bean instances of the instance's

life cycle events.

Method Summary:

void ejbActivate()

The activate method is called when the instance is activated from its "passive"

state.

void ejbPassivate()

The passivate method is called before the instance enters the "passive" state.

void ejbRemove()

A container invokes this method before it ends the life of the session object.

void setSessionContext(SessionContext ctx)

Set the associated session context.


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javax. EJB Server InterfacesCont.

EntityContext

getEJBObject()getPrimaryKey()

SessionContext

getEJBObject()

EJBContext

getEJBHome()getEnvironment()getCallerIdentity()isCallerInRole()

getUserTransaction()setRollBackOnly()

The SessionContext interface

A container provides the session bean instances with a SessionContext, which gives the

session

bean instance access to the instances context maintained by the container. This give

information about the beans home object, current transaction information, security role

information. The SessionContextinterface has the following methods:

The getEJBObject method returns the session beans remote interface.

The getEJBHome method returns the session beans home interface.

The getCallerPrincipal method returns the java.security.Principal that identifies the invoker

of the bean instances EJB object.

The isCallerInRole method tests if the session bean instances caller has a particular role.

The setRollbackOnly method allows the instance to mark the current transaction such that

the only outcome of the transaction is a rollback. Only instances of a session bean with

container-managed transaction demarcation can use this method.

The getRollbackOnly method allows the instance to test if the current transaction has been

marked for rollback. Only instances of a session bean with container-managed transactiondemarcation can use this method.

The getUserTransaction method returns the javax.transaction.UserTransaction interface.

The instance can use this interface to demarcate transactions and to obtain transaction status.

Only instances of a session bean with bean-managed transaction demarcation can use this

method.


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Differences From Entity Bean

Session Implements

SessionBeaninterface

Does not use primarykey object

Uses create methodto create instance,stateful to initializelocal data

Entity

ImplementsEntityBean interface

Uses primary keyobject

Uses create, andcallback methods tocreate,store/updatedata in database

Session EJB objects are created, associated with a specific client, and then

removed as needed, whereas entity EJB objects represent permanent

data in a data storage that can be uniquely identified with a primary key.

Because the instance data for session beans is not persistent, the session bean

class does not have callback methods for storing data to and loading data

from a data source.


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1 . Create the remote interface for thebean.


3. Create the beans implementation class.



6. Package in an ejb-jar file.

7. Deploy the enterprise application.







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1 ) Create the Remote Interface

public interface Atm extends javax. ejb.EJBObject {

public void transfer(int fromAcctId, int toAcctId, double amount)throws java.rmi.RemoteException,InsufficientFundsException;

}

EJBObject

Atm

transfer()

extends

Define Business Methods:

Session beans remote interface

The following are the requirements for the session beans remote interface:

The interface must extend the javax.ejb.EJBObject interface.

The methods defined in this interface must follow the rules for RMI/IIOP.

This means that their arguments and return values must be of valid types forRMI/IIOP, and their throws clause must include the

java.rmi.RemoteException.

The remote interface is allowed to have super interfaces. Use of interface

inheritance is subject to the RMI/IIOP rules for the definition of remote

interfaces.

For each method defined in the remote interface, there must be a matching

method in the session beans class. The matching method must have:

The same name.

The same number and types of arguments, and the same return type. All the exceptions defined in the throws clause of the matching

method of the session bean class must be defined in the throws clause

of the method of the remote interface.


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2) Create the Home Interface

public interface AtmHome extends javax.ejb.EJBHome {

Atm create() throws java.rmi.RemoteException,javax.ejb.CreateException;

}

EJBHome

AtmHome

create()

Returns Atmremote interface

Define Create Methods:

Session beans home interface requirements:

The interface must extend the javax.ejb.EJBHome interface.

The methods defined in this interface must follow the rules for RMI/IIOP. This means that

their arguments and return values must be of valid types for RMI/IIOP, and that their throws

clause must include the java.rmi.RemoteException.

The home interface is allowed to have superinterfaces. Use of interface inheritance is subjectto the RMI/IIOP rules for the definition of remote interfaces.

A session beans home interface must define one or more create(...) methods. (stateless only

1)

Each create method must be named create, and it must match one of the ejbCreate methods

defined in the session bean class. The matching ejbCreate method must have the same number

and types of arguments. (Note that the return type is different.) (stateless no arguments)

The return type for a create method must be the session beans remote interface type.

All the exceptions defined in the throws clause of an ejbCreate method of the session bean

class must be defined in the throws clause of the matching create method of the home inter-

face.

The throws clause must include javax.ejb.CreateException.


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3. Create the beans implementationclass.



6. Package in an ejb-jar file.7. Deploy the enterprise application.






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3) AtmBean Implementation

AtmBean

transfer()ejbCreate()


ejbPassivate()

implements

Atm

transfer()

AtmHome

create()

must matchfor containerglue

SessionBean


ejbPassivate()

The following are the requirements for the session bean class:

must implement the javax.ejb.SessionBean interface.

must be defined as public, must not be final, and must not be abstract.

must have a public constructor that takes no parameters. The Container uses

this constructor to create instances of the session bean class.

must not define the finalize() method.

must implement the business methods and the ejbCreate methods.

If the class is a stateful session bean, it may optionally implement the

javax.ejb.SessionSynchronization interface.

The session bean class may have superclasses and/or superinterfaces. If the

session bean has superclasses, then the business methods, the ejbCreate

methods, the methods of the SessionBean interface, and the methods of the

optional SessionSynchronization interface may be defined in the session bean

class, or in any of its superclasses.The session bean class is allowed to implement other methods (for example

helper methods invoked internally by the business methods) in addition to the

methods required by the EJB specification.


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Lifecycle of a Stateless SessionBean

method-readypool

EJBInstance

ejbRemove()

business method

does not

exist

1) newInstance()

2) setSessioncontext()

3)ejbCreate()


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Invocation of a Business Method

clientbean

instanceEJB

HomeEJB

Objectsessioncontext

synchro

nization

trans

action

data

base

business method

business method

read, update data

register resource mgr


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Creating a Stateless Session BeanInstance

clientbean

instanceEJBHome EJBObject context

create()

new


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Adding Instance of Stateless SessionBean to a Method- ready Pool

clientbean

instanceEJB

HomeEJB


synchro-

nization

trans

action

data

base

cont-

ainer

new

new

setSessionContext()

ejbCreate()


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3) AtmBean: Implement HomeInterface Create Method

// implement atmHome interface createprivate static AccountHome accountHome = null;public void ejbCreate (){try {

Context ic = new InitialContext();

java.lang. Object objref = ic.lookup("java:comp/env/ejb/Account");accountHome=(AccountHome)PortableRemoteObject.narrow(objref,

AccountHome. class);} catch (NamingException ne) {

System.err.println("ejbCreate: Caught unexpectedNamingException:");

}}EXAMPLE DEPLOYMENT DESCRIPTOR XML FOR EJB REFERENCE< ejb- ref>

< ejb- ref-name> ejb/Account< /ejb-ref-name>< ejb- ref-type> Entity< /ejb-ref-type>< home> package. AccountHome< /home>< remote> package. Account< /remote>< /ejb-ref>

Returns void

Bean create methods must match the methods defined in this EJB's home interface, AtmHome.

Container tools generate the implementation of the AtmHome class and the client stub and

server skeleton classes. Calls on those classes will be forwarded to the AtmBean.

A stateless session bean must have only one ejbCreate method, which must return void and

contain no arguments. In a stateless session bean, none of the methods depend on the values

of variables set by any other method, except for the ejbCreate, setSessionContext methods

which set the initial (identical) state of each bean instance. The term stateless signifies that

an instance has no state for a specific client. However, the instance variables of the stateless

session bean can contain non-client specific state across client-invoked method calls.

Examples of such states include an open database connection or an object reference to an

EJB object.

ejbCreate method

The stateless session bean class must define one ejbCreate(...) methods whose signature must

follow these rules:

The method name must be ejbCreate.

The method must be declared as public.

The method must not be declared as final or static.

The return type must be void.

The methods arguments must be legal types for RMI/IIOP.

The throws clause may define arbitrary application exceptions, possibly including the

javax.ejb.CreateException.


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Removing Instance of StatelessSession Bean From Ready Pool

clientbean

instanceEJB

HomeEJB


synchro-

nization

trans

action

data

base

cont-

ainer

ejbRemove()


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Removal of a Stateless SessionBean Instance

clientbean

instanceEJBHome EJBObject context

remove()


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3) AtmBean: Implement SessionInterface Container Callback Methods

// save the session context in an instance variablepublic void setSessionContext(SessionContext sc) {this.context= sc;

}

// release resources allocated in ejbCreatepublic void ejbRemove() throws RemoveException {

accountHome = null;}

// Stateless Session Beans are not activated/passivated// so these methods are always emptypublic void ejbActivate() {}public void ejbPassivate() {}

Bean callback methods:

The container uses these to alert the bean of runtime events. Each method is

called at a specific time during the life cycle of a bean.

The beans container calls the setSessionContext method to associate a

session bean instance with its context maintained by the container. Typically,a session bean instance retains its session context as part of its

conversational state.

The ejbRemove notification signals that the instance is in the process of being

removed by the container. In the ejbRemove method, the instance typically

releases the resources that it allocated in the ejbCreate method.

ejbActivate/ejbPassivate:

All Stateless Session bean instances are equivalent when they are not involved

in serving a client-invoked method. A container only needs to retain the

number of instances required to service the current client load. Due to client

think time, this number is typically much smaller than the number of activeclients. Passivation is not needed for stateless sessions. The container

creates another stateless session bean instance if one is needed to handle an

increase in client work load. If a stateless session bean is not needed to handle

the current client work load, the container can destroy it.


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Lifecycle of a Stateless SessionBean

method-readypool

EJBInstance

ejbRemove()

business method

does not

exist

1) newInstance()

2) setSessioncontext()

3)ejbCreate()


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4) Compile the Remote & Home Interfaces andImplementation Class.

javac classpath $J2EE_HOME/lib/j2ee.jarAtm.java AtmHome.javaAtmEJB.java


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Define a deployment descriptor specifying any declarative metadata that the

session Bean provider wishes to pass with the Bean to the next stage of the

development/deployment work-flow.


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XML Short Intro

The XML Companion

Neil Bradley

Addison-Wesley

Processing Instruction (PI)

Document Type Definition(DTD)

Element

Attribute

Processing Instruction (PI)

Document Type Definition(DTD)

Element

Attribute


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EJB descriptor composition


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5) Create Deployment Descriptor

Set the values for the class names,

transaction attributes,

Environment values,resource references,

EJB references


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This example sets the EJB reference for referencing the Account Bean.

Example code in the AtmEJB for referencing the Account Bean:

Context ic = new InitialContext();

java.lang.Object objref = ic.lookup("java:comp/env/ejb/Account");

accountHome=(AccountHome)PortableRemoteObject.narrow(objref,

AccountHome.class);


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This example show setting the transaction attributes. We will go over

transactions in Lecture 4. Here we set the method transfer to transaction

required because we want to make sure that the transfer takes place in a

transaction, so that either both the credit and debit accounts are updated or

NO accounts are updated.


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5) Create DD Cont.

AtmBean

Remote

transfer

Required


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6. Package in an ejb- jar file.



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6) Package in an ejb- jar File.

AtmAtmHomeInterfaces

AtmEJBbean

Deployment

Descriptor

XML DD

packager ejbJarAtm.class:AtmEJB.class:AtmHome.classAtm-ejb-jar.xml Atm.jar


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6) Package in an ejb- jar File.


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7) Deploy the EnterpriseApplication

Deployment tool

Deployment tool

Client Jar: : Atm, AccountEJBHome EJBObject

Interfaces & Stubs

Server Jar: Atm and AccountEJBHome EJBObject

Stubs and Object implementationsEnterprise Beans

Application jar: Atm, AccountEJBHome EJBObject interfaces,Atm, Account beans

AtmEJB.jar,Account.EJBjar

J2EE Reference Implementation Deployment: Behind the Scenes

1. The J2EE process opens the application JAR file, reads the deployment descriptors, and

generates the home interface and EJBObject implementation for each Bean.

2. The J2EE process compiles the home interface and the EJBObject implementations and

then runs the rmic command on the class files. This step creates the stubs and skeletons

for the home and remote objects.3. The server packages the generated classes into a server JAR file and stores the JAR file

in the repository.

4. The server creates a client JAR file that contains the home and remote interfaces and

the stubs for the home and remote objects. The server sends the client JAR file to the

deployer and saves the file according to the name chosen at the start of the deployment

process.

5. The location of the client JAR file must be added to the CLASSPATH environment

variable on any client that calls the application. Then, at runtime, the appropriate stub

classes can be loaded so that the client can successfully locate objects, for example, the

home object for an enterprise bean in the application.

6. The J2EE server starts a process which loads the server JAR file and creates containers

for the enterprise beans and binds the beans to the JNDI names in the name server.

7. At this point, the deployment process is complete.


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Example of Deployment of Bank Application .ear consisting of Atm Session

EJB .jar and Account Entity EJB .jar.


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Create a Client

1. Use JNDI to lookup EJBs homeinterface.

2. Call homes create method to get theEJB remote object interface.

3. Call beans business methods thruremote interface.


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ATM Client Code

// create an initial context (starting point in name tree)javax. naming.Context ic =newjavax. naming. InitialContext();

// lookup jndi name (set by deployer in deploymentdescriptor)java. lang.Object objref = ic. lookup("Atm");

AtmHome home = (AtmHome)PortableRemoteObject. narrow(objref, AtmHome.class);

//call AtmHome Create method to get Atm interfaceAtm atm = home. create();

// call Atm business methodsatm. transfer(41476633, 4443332121, 100000);

1) Use JNDI name services to locate a name server:

Create an InitialContext (starting point) with server environment properties.

2)lookup the Atm EJBHome interface using the JNDI name given in

deployment descriptor

-lookup returns a stub reference to the object implementation of AccountHome

3)call create to get a reference to the Atm EJBObject stub.

4)call Atm business methods


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Session Bean Accessing Entity Bean

Client

server

JNDI nameservice

EJBObject

AccountBean

EJBHome

AccountBean

EJBObject

AtmBean

EJBObjecttransferfind

withdraw

deposit

find

Example of Sequence of events for Client calling the Transfer method on the

Atm remote interface stub.


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Exercise: Design and ImplementCatalog Stateless Session Bean

customerList Books in Store

customerSearch for books by subject

Use Case Scenarios

customerGet Book Details (by ISBN)

1)Customer finds book by ISBN

2)Customer searches for books by subject, author title.


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Stateless Services:Catalog Session EJB

product

ISBN

title

author

description

A Catalog object represents different products and provides

br owsing and searching services to its clients. Both of the primary functio

of the catalog, browsing and searching, are generic services which are not

tied to any par ticular client . Also, the catalog object reads multiple rows

in the database at the same time and provides a shar ed view of the data.

CatalogEJB

getBooks()

getBookDetails()

findBooksBySubject()

ejbCreate()

setSessionContext()

ejbRemove()

ejbActivate()

ejbPassivate()


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CatalogEJB

CatalogEJB

getBooks()

getBookDetails()


ejbCreate()

setSessionContext()

ejbRemove()

ejbActivate()

ejbPassivate()

BookDeta i ls

I S B N

ti t le

a u th o r

p u b l i s h e r

s u b j e c t

d e s c r ip t io n

p r i c e

g e t ISBN()

getT i t le ()

g e tAu th o r ( )

g e tP r i c e ( )

g e tDe s c r ip t io n ( )

g e tPu b l i s h e r ( )

Catalog

getBooks()

getBookDetails()


CatalogHome

create()

deploying a stateless ejb

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