Ejb training institute in navi-mumbai

WELCOME TO VIBRANT
TECHNOLOGIES & COMPUTERS
--------------------------
ONLINE EJB TRAINING PPTS
Address: K1/4 2nd Floor,Sec-15/16 Market Opp to Vaidehi
Hotel, Vashi, Navi Mumbai, Maharashtra 400703
Phone:098929 00103

Contact Us On : Vibranttechnologies.co.in

∗ What is EJB?
∗ Key features of EJB technology
∗ EJB vs JavaBeans
∗ Varieties of Beans
∗ Why use EJBs in your design?
∗ EJB Architecture
∗ EJB Container and its Services
∗ Services provided by an EJB container
∗ How the Container Provides Services
∗ Contracts
∗ Rules for the bean programmer
∗ Interposition : method call to an EJB Container from a remote client
∗ Interposition diagram
∗ Working with EJBs
∗ EJB Clients
∗ The Client Developer’s View
∗ EJB’s interface
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www.vibranttechnologies.co.in
Content :

∗ Client.java
∗ Client contd..
∗ The Bean Programmer’s view
∗ Interface EJB Object
∗ Order Management code..
∗ Order ManagementBean code..
∗ Interface EJBHome
∗ The xml file : ejb-jar.xml
∗ Structure of JAR file
∗ What you can’t do in an EJB component?
∗ EJB Components on the Web
∗ Implementation of MVC in a web site
∗ Design of the EJB Tier
∗ Analysis Objects
∗ View of interaction between control
∗ objects and entity objects
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Content :

∗ An EJB is just a collection of Java classes and XML file,
bundled into a single unit. The Java classes must
follow certain rules and provide certain callback
methods.
∗ EJB is just a specification. It is not a product.
∗ EJBs are reusable components.
What is EJB?
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∗ EJB is a widely-adopted server-side component
architecture for J2EE.
∗ EJB components are designed to encapsulate
business logic, and to protect the application
developer from having to worry about system level
issues.
What is EJB?
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∗ EJB components are server-side components
written entirely in the Java programming
language
∗ EJB components contain business logic only - no
System-level programming
∗ System-level services (i.e. "plumbing") such as
transactions, security, Life-cycle, threading,
persistence, etc. are automatically managed for
the EJB component by the EJB server
Key features of EJB technology
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∗ EJB architecture is inherently transactional,
distributed, portable, multi-tier, scalable and secure
∗ EJB components are fully portable across any EJB
server and any OS, work with any client.
∗ Components are declaratively customized
∗ There are four major parts to every bean: the home
interface, the remote interface, the implementation
class and the XML deployment descriptor
Key features of EJB technology
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∗ The JavaBeans architecture is meant to provide a
format for general-purpose components whereas the
EJB architecture provides a format for encapsulation
and management of business logic.
∗ JavaBeans has tier of execution at Client and EJB has
at Server (specifically business logic tier)
EJB vs JavaBeans
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∗ In JavaBeans the runtime execution environment
provides services like Java libraries, Java application
etc. The EJB runtime environment provides services
of Persistence, declarative transactions and security,
connection pooling and lifecycle services.
EJB vs JavaBeans
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∗ Session Beans
Stateful session bean
Stateless session bean
∗ Entity Beans
With container-managed persistence
With bean-managed persistence
∗ Message-Driven Beans
Varieties of Beans
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∗ EJB specification provides enterprise-level services,
that is, it provides software services that are
fundamental to an organization’s purpose.
∗ EJB’s API was designed to keep the application
programmer from having to provide systems-level
services, so that they are free to concentrate on
business logic.
Why use EJBs in your design?
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∗ A requirement of any of the services provided by an
EJB container like transactions, scalability,
persistence, security, future growth possibilities is an
appropriate reason to use EJB in the design of the
application.
Why use EJBs in your design?
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EJB Architecture
J2EE Application Server
EJB Container
Application Logic DataClient
RDBMS
Corba
Mail
RMI
JDBC
Java
Mail
JMS
JTA
Session Bean
Entity Bean
Client
Application

∗ EJB provider - a person who develops EJB Components
∗ EJB Deployer - a person responsible for deploying EJB’s in
EJB server
∗ Application Server/ EJB Container Vendor - one who
provides application server on which the application is
deployed
Roles in EJB Development
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∗ Application assembler - one who combine the EJB
components with other software to make a complete
application
∗ System administrator - one who manages the
application after it has been deployed into a target
environment.
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EJB
Provider
Application
Assembler
App Server/
EJB Container
Provider
Deployer
System
Administrator

∗ A container is an execution environment for a
component. The component lives in the container and
the container provides the services for the
component.
∗ Similarly, a container lives in an application server,
which provides an execution environment for it and
other containers.
EJB Container and its Services
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∗ Persistence
Ex: simple connection pooling, automatic
persistence, etc. EJBs created with application
development tools will encapsulate data access in
components.
Services provided by an EJB container
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∗ Declarative transactions
∗ Data caching
∗ Declarative Security
∗ Error Handling
∗ Component Framework for Business Logic
∗ Scalability and Fall-Over
∗ Portability
∗ Manageability
Services provided by an EJB container
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There are three basic ideas:
∗ First, there are clearly defined responsibilities between the
various parts of an application using EJB component
namely the client, the EJB container and the EJB
component. The definition of these responsibilities is
formally known as a contract.
∗ Second, the services that the container provides are
defined in such a way that they are orthogonal to the
component. In other words, security, persistence,
transactions are separate from the Java files that
implement the business logic of the component.
How the Container Provides Services
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∗ Third, the container interposes on each and every call
to an EJB component so that it can provide its
services. In other words, the container puts itself
between the client and the component on every
single business method call.
How the Container Provides Services
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Contracts
EJB Container/Application
Server
Enterprise JavaBean
Client
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∗ The developer of the EJB component must implement the
business methods in the implementation class
∗ The bean provider must implement the ejbCreate(),
ejbPostCreate(),ejbRemove() methods and the
ejbFind<METHOD>() methods if the bean is an entity with
bean managed persistence
∗ The bean provider must define the enterprise bean’s home
and remote interfaces
∗ For session beans, the bean provider must implement the
container callbacks defined in the javax.ejb.SessionBean
interface
Rules for the bean programmer
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∗ For entity beans, the provider must implement the
container callbacks defined in the
javax.ejb.EntityBean interface
∗ The bean provider must not use programming
practices that would interfere with the container’s
runtime management of the enterprise bean
instances
Rules for the bean programmer
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∗ First, the client makes a call on the RMI stub
∗ This RMI stub interposes on the method call in order
to marshal parameters and send the information
across the network
∗ A skeleton on the server side unmarshals the
parameters and delivers them to the EJB Container
Interposition : method call to an EJB
Container from a remote client
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Interposition diagram
Interposition class
Client
Container
generated
class
EJB
RMI
Stub
RMI
Stub
Network

∗ The container will examine the security credentials of the
caller of the method
∗ It will start or join with any required transactions
∗ It will make any necessary calls to persistence functions
∗ It will trigger various callbacks to allow the EJB
Component to acquire resources
∗ Only after all this is done will the actual business method
be called
∗ Once it is called, the container will do some more work
with transactions, persistence, callbacks and returns data
or exception to the remote client
Interposition : from EJB Container
to EJBs
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The Enterprise JavaBeans specification is written for
three audiences:
∗ The Client developer
∗ The EJB developer
∗ The EJB container developer
Working with EJBs
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∗ EJB Clients are applications that access EJB
components in EJB containers. There are two
possible types. The first category is application
clients which are stand-alone applications
accessing the EJB components using the RMI-
IIOP protocol. The second category of application
clients are components in the web container.
They are java servlets and JSPs which also access
the EJB components via the RMI-IIOP protocol.
EJB Clients
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∗ The client has a smaller set of concerns then a bean
developer with regard to using EJBs. Basically, he
need to know :
how to find or create a bean,
how to use its methods and
how to release its resources
∗ The client need not worry about the implementation
of the EJB, callbacks that the EJB container will make
on the EJB or nature of the services provided to the
EJB.
The Client Developer’s View
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∗ Home Interface : It is primarily for the life cycle
operations of the bean: creating, finding, and
removing EJBs. The home interface is not
associated with a particular bean, just with a type
of bean.
∗ Remote Interface : It is for business methods.
Logically, it represents a particular bean on the
server. The remote interface also provides some
infrastructure methods associated with a bean
instance, rather than a bean type.
EJB’s interface
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∗ A client programmer will acquire an EJB’s
home interface through JNDI, and they use
this home interface to :
Sample client application
pseudo code
Create or find
instance of bean
Execute methods Reference
(Handle)
Remove bean
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Package orderMgmt;
import java.util.properties;
import java.naming.Context; // for name-to-object findings
import java.naming.InitialContext;// context for naming operations
public class Client {
try {
Properties prop = new Properties();
// server dependent properties for InitialContext
prop.put(Context.INITIAL_CONTEXT_FACTORY,
“org.jnp.interfaces.NamingContextFactory”);
prop.put(Context.PROVIDER_URL, “localhost:1099”);
Context ctx = new InitialContext(prop);
Object objref = ctx.lookup(“OrderManagement”);
Client.java
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// casting home interface reference to the OrderManagementHome
OrderManagementHome home = (OrderManagementHome)
javax.rmi.PortableRemoteObject.narrow(objref,
OrderManagementHome.class);
// home interface to create an instance of the OrderManagement
OrderManagement orderManagement = home.create();
// calling placeOrder()
orderManagement.placeOrder("Dan OConnor",
"Wrox books on programming", 1000);
orderManagement.remove();
System.out.println("Order successfully placed.");
} catch (Exception e) { e.printStackTrace(); }
} }
Client contd..
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∗ Main responsibility is write business logic and
structure the code in a particular structure. The
structure has 4 files, the home interface, remote
interface, business logic class file and the XML
file. The XML file called the deployment
descriptor, contains the structural information
about the bean, declares the bean’s external
dependencies and specifies certain information
about how services such as transaction and
security work.
The Bean Programmer’s view
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package javax.ejb;
public interface javax.ejb.EJBObject extends java.rmi.Remote {
EJBHome getEJBHome() throws java.rmi.RemoteException;
Handle getHandle() throws java.rmi.RemoteException;
Object getPrimaryKey() throws java.rmi.RemoteException;
boolean isIdentical(EJBObject obj) throws
java.rmi.RemoteException;
void remove() throws java.rmi.RemoteException;
}
Interface EJB Object
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∗ package orderMgmt;
∗ import javax.ejb.*;
∗ public interface OrderManagement extends javax.ejb.EJBObject
∗ {
∗ public void placeOrder(String custName, String prodName, int quantity)
throws java.rmi.RemoteException;
∗ public void cancelOrder(String custName, String prodName)
∗ throws java.rmi.RemoteException;
∗ public boolean isShipped(String custName, String prodName) throws
∗ }
Order Management code..
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∗ public class OrderManagementEJB implements javax.ejb.SessionBean
∗ {
∗ public void placeOrder(String custName, String prodName, int
quantity)
∗ { // ... Business logic ...}
∗ public void cancelOrder(String custName, String prodName)
∗ { // ... Business logic ...}
∗ public boolean isShipped(String custName, String prodName)
∗ { // ... Business logic … return true; }
Order ManagementBean code..
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∗ public void ejbCreate()
∗ { // Can be empty }
∗ public void ejbRemove()
∗ { // Can be empty }
∗ public void ejbActivate()
∗ { // Can be empty}
∗ public void ejbPassivate()
∗ public void setSessionContext( SessionContext ctx )
∗ }
OrderManagementBean code..
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Package javax.ejb;
public interface EJBHome extends java.rmi.Remote {
EJBMetaData getEJBMetaData () throws
HomeHandle getHomeHandle() throws java.rmi.RemoteException;
void remove(Handle handle) throws java.rmi.RemoteException,
java.ejb.RemoveException;
void remove(Object primary key) throws
java.rmi.RemoteException, java.ejb.RemoveException;
}
Interface EJBHome
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∗ public interface OrderManagementHome extends
javax.ejb.EJBHome
∗ {
∗ public OrderManagement create()
∗ throws java.rmi.RemoteException,
javax.ejb.CreateException;
∗ }
OrderManagementHome code..
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<?xml version=“1.0”?>
<ejb-jar>
<enterprise-beans>
<session>
<ejb-name>OrderManagement</ejb-name>
<home>orderMgmt.OrderManagementHome</home>
<remote>orderMgmt.OrderManagement</remote>
<ejb-class>orderMgmt.OrderManagementBean</ejb-class>
<session-type>Stateless</session-type>
<transaction-type>Container</transaction-type>
</session>
</enterprise-beans>
The xml file : ejb-jar.xml
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<assembly-descriptor>
<container-transaction>
<method>
<ejb-name>OrderManagement</ejb-name>
<method-name>*</method-name>
</method>
<trans-attribute>Required</trans-attribute>
</container-transaction>
</assembly-descriptor>
</ejb-jar>
The xml file : ejb-jar.xml
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META -INF
ejb-jar.xml
orderMgmt
OrderManagement.class
OrderManagementHome.class
OrderManagementBean.class
Structure of JAR file
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∗ You cannot use Reflection API to access
information inaccessible to you.
∗ You cannot create a class loader or replace a
security manager.
∗ You cannot set the socket factory used by
ServerSocket or Socket
∗ You cannot use the object substitution
features of the serialization protocol
What you can’t do in an EJB component?
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∗ use Threads or the Threading API
∗ use the AWT
∗ Act as a Network Server
∗ use Read/Write static fields
∗ use java.io package
∗ Load a native library
∗ use “this” as an Argument or Return value
∗ use Loopback Calls
What you can’t do in an EJB
component?
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Three classes of objects in MVC architecture:
∗ Model : This is the data and business-logic
component. It can serve multiple views.
∗ View : This is the presentation component or the user-
interface component. There can be different
presentations of a single model.
∗ Controller : This is the component that responds to
user input. Translates user-interface events into
changes to the model and defines the way the user-
interface reacts to those events.
EJB Components on the
Web
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Implementation of MVC in a web site
Controller
Model
Browser
Client
view1.jsp
view2.jsp
view3.jsp
Main.jsp
Views
1
2
3
4
5

∗ UML use cases: UML is the Unified Modeling
Language, the standard language for expressing the
model of the software system that we intend to build.
∗ Use cases are subset of UML that expresses the
functionality of the software to be delivered. Use
cases describe what to do, but not how to do it.
Design of the EJB Tier
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∗ Interface Objects : The interface object is responsible
for controlling access to the EJB tier from any client.
An interface object should always be represented by a
session bean in the implementation.
Ex : controller servlet for the web application’s model-
view-controller architecture.
Analysis Objects
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∗ Control objects provide services to the application.
They model functionality that is not naturally
associated with a particular entity or interface.
Control objects should be represented by session
beans in the implementation.
Control Objects
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∗ Entity objects model those business objects that
should maintain their state after the use case
completes. This means they represent data in the
database. Entity beans are often represented by
entity beans in the implementation model.
Entity Objects
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∗ Consider the case of a company that develops
products, takes orders for those products, and
then manufactures and ships them.
∗ Actors in the company : An engineer, a web
customer, a phone operator who takes orders
from a catalog, floor manager who manages the
manufacturing process, a crew member that
actually builds the product ordered and a
manager who tracks overdue orders.
An Example of EJB Design
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∗ Create a Product
∗ Place an Order
∗ Cancel an Order
∗ Select an Order for Manufacture
∗ Build a Product
∗ Ship an Order
∗ List Overdue Orders
Use Cases
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Use case diagram from analysis
Engineer
Customer
Operator
Manager
Crew
M’ment
Create Product
Place Order
Cancel Order
Select Order
Build Product
Ship an Order
Overdue Orders

∗ Interface Object :
Stereotype icons in UML
Entity Object :
Control Object :

∗ Actor User Interface Type Interface Object Impl’ation
Engineer Visual Basic Session Bean (RMI/IIOP)
Customer Web Application JavaBean proxy / S Bean
Operator Swing GUI Session Bean
Manager Web Application JavaBean proxy / S Bean
Crew Palm Pilot XHTML Servelet to Session Bean
Management Web Application JavaBean proxy / S Bean
Translation of analysis model into implementation

View of use case actors and their
respective interface objects
Engineer
Customer
Operator
Manager
Crew
Manage-
-ment
VB App
Web App
Swing app
Web App
Web App
Palm App

View of interaction of interface
and control objects
Ship
order
Build
Product
Select
Cancel
Place
Create
List
Overdue
VB
App
Web
App
Web
App
Web
App
Swing
App
Palm
App

View of interaction between control
objects and entity objects
RoutingProduct
Order
Shipment
Account
Supplier
Shipping
Company
Customer
Create
Product
Place
Order
Cancel
Order
Select for
Manufacture
Build
Product
Ship
Order
List
Overdue

∗ EJBs are intended for transactional systems
∗ EJBs are portable, reusable server-side
components that execute in a container
∗ Assist developer productivity, extend application
capability, and improve system stability
∗ Are accessible from many different types of
clients
∗ There are three types of beans : stateful session,
stateless session, and entity
Summary
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∗ There are four major parts to every bean: the
home interface, the remote interface, the
implementation class, and the XML deployment
descriptor
∗ The enterprise bean developer must follow
certain rules to get the benefits of EJB
technology
∗ The roles of EJBs can be understood by analyzing
a model of your enterprise in terms of interface,
control and entity objects
Summary
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Ejb training institute in navi-mumbai

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