Creating Session Beans

Сентябрь 15, 2022

Главная
Алгебра
Creating Session Beans

Содержание

2. Objectives After completing this lesson, you should be able to: Describe session beans Create stateless and
3. What Is a Session Bean? A session bean is a type of Enterprise JavaBean (EJB) that:
4. Stateless Versus Stateful Session Beans There are two types of session beans: Stateless session bean (SLSB)
5. Life Cycle of a Stateless Session Bean Ready Creation Does not exist Destruction Method
6. Creating a Stateless Session Bean To create a stateless session bean: Define the stateless session bean.
7. Define the Stateless Session Bean // HelloWorldBean.java package helloworld.ejb import javax.ejb.Stateless; @Stateless(name="HelloWorld") public class HelloWorldBean implements
8. Create the Remote and Local Interfaces // HelloWorld.java package helloworld.ejb import javax.ejb.Remote; @Remote public interface HelloWorld
9. Create a Test Client for the SLSB // HelloWorldClient.java import helloworld.ejb; import javax.naming.Context; import javax.naming.InitialContext; import
10. Life Cycle of a Stateful Session Bean Ready Creation Passive Activation Passivation Does not exist Destruction
12. Passivation and Activation Concepts Passivation and activation are stages in a session bean’s life cycle controlled
13. Creating a Stateful Session Bean To create a stateful session bean: Define the stateful session bean.
14. Define the Stateful Session Bean // CartBean.java package cart.ejb import javax.ejb.Stateful; … @Stateful(name="Cart") public class CartBean
15. Create the Remote and Local Interfaces // Cart.java package cart.ejb import javax.ejb.Remote; … @Remote public interface
16. Create a Test Client for the SFSB // CartClient.java import … public class CartClient { public
17. Interceptor Methods and Classes EJB 3.0 introduces the ability to create custom interceptor methods and classes
18. Interceptor Method import javax.ejb.Stateless; import javax.ejb.AroundInvoke; import javax.ejb.InvocationContext; @Stateless public class HelloWorldBean implements HelloWorld { @AroundInvoke
19. Interceptor Classes External interceptor classes can be created to abstract the behavior of interceptors and to
20. Summary In this lesson, you should have learned how to: Describe session beans Create stateless and
22. Скачать презентацию

Слайд 2

Objectives
After completing this lesson, you should be able to:
Describe session beans
Create

stateless and stateful session beans by using annotations
Understand the passivation and activation of stateful session beans
Use interceptor methods and classes

Слайд 3

What Is a Session Bean?
A session bean is a type of

Enterprise JavaBean (EJB) that:
Implements a business process
Represents a client/server interaction
Has a short lifespan
Lives in memory rather than in persistent storage
Is used to create a session facade

Слайд 4

Stateless Versus Stateful Session Beans
There are two types of session beans:
Stateless

session bean (SLSB)
Conversation is contained in a single method call.
Business process does not maintain client state.
Stateful session bean (SFSB)
Conversation may invoke many methods.
Business processes can span multiple method requests, which may require maintaining state.

EJB container

Client 1

Client 2

Pool of SLSBs

EJB container

Client 1

Client 2

SFSBs

Слайд 5

Life Cycle of a Stateless Session Bean
Ready
Creation
Does not exist
Destruction
Method

Слайд 6

Creating a Stateless Session Bean
To create a stateless session bean:
Define the

stateless session bean.
Define the local and remote interfaces (as needed).

Слайд 7

Define the Stateless Session Bean
// HelloWorldBean.java
package helloworld.ejb
import javax.ejb.Stateless;
@Stateless(name="HelloWorld")
public class HelloWorldBean implements

HelloWorld
{
public void sayHello()
{
System.out.println("Hello World!");
}
}

Слайд 8

Create the Remote and Local Interfaces
// HelloWorld.java
package helloworld.ejb
import javax.ejb.Remote;
@Remote
public interface HelloWorld

{
public void sayHello();
}

// HelloWorldLocal.java
package helloworld.ejb
import javax.ejb.Local;
@Local
public interface HelloWorldLocal {
public void sayHello();
}

Слайд 9

Create a Test Client for the SLSB
// HelloWorldClient.java
import helloworld.ejb;
import javax.naming.Context;
import javax.naming.InitialContext;
import

javax.naming.NamingException;
public class HelloWorldClient {
public static void main(String [] args)
throws NamingException {
try {
final Context context = new InitialContext();
HelloWorld helloWorld =
(HelloWorld)context.lookup("HelloWorld");
helloWorld.sayHello( );
} catch (Exception ex) { ex.printStackTrace(); }
};
}

Слайд 10

Life Cycle of a Stateful Session Bean
Ready
Creation
Passive
Activation
Passivation
Does not exist
Destruction
Ready (in TX)
Commit/
rollback
TX

Method

TX method

Timeout

Слайд 11

Слайд 12

Passivation and Activation Concepts
Passivation and activation are stages in a session

bean’s life cycle controlled by the EJB container:
Passivation
Serializes the bean state to secondary storage
Removes the instance from memory
Activation
Restores the serialized bean’s state from secondary storage
Creates a new bean instance or uses a bean from the pool (initialized with the restored state)

Слайд 13

Creating a Stateful Session Bean
To create a stateful session bean:
Define

the stateful session bean.
Define the local and remote interfaces (as needed).

Слайд 14

Define the Stateful Session Bean
// CartBean.java
package cart.ejb
import javax.ejb.Stateful;
…
@Stateful(name="Cart")
public class CartBean implements

Cart {
private ArrayList items;
@PostConstruct
public void initialize() { items = new ArrayList(); }
public void addItem(String item) { items.add(item); }
public void removeItem(String item) { items.remove(item); }
public Collection getItems() { return items; }
@Remove
public void dumpCart() {System.out.println("BYE!");};
}

Слайд 15

Create the Remote and Local Interfaces
// Cart.java
package cart.ejb
import javax.ejb.Remote;
…
@Remote
public interface Cart

{
public void addItem(String item);
public void removeItem(String item);
public Collection getItems();
}

// CartLocal.java
package cart.ejb
import javax.ejb.Local;
…
@Local
public interface CartLocal { …

Слайд 16

Create a Test Client for the SFSB
// CartClient.java
import …
public class CartClient

{
public static void main(String[] args) throws Exception {
Context context = new InitialContext();
Cart cart = (Cart) context.lookup("Cart");
cart.addItem("Item1");
cart.addItem("Item2");
Collection items = cart.getItems();
for (Iterator i = items.iterator(); i.hasNext();) {
String item = (String) i.next();
System.out.println(" " + item);
}
cart.dumpCart();
}
}

Слайд 17

Interceptor Methods and Classes
EJB 3.0 introduces the ability to create custom

interceptor methods and classes that are called before invoking the methods they intercept. Interceptors:
Are available for only session beans (stateless and stateful) and message-driven beans
Provide more granular control of a bean’s method invocation flow
Can be used to implement custom transaction or security processes instead of having those services provided by the EJB container
Are a new feature whose implementation details are not fully defined and are subject to change

Слайд 18

Interceptor Method
import javax.ejb.Stateless;
import javax.ejb.AroundInvoke;
import javax.ejb.InvocationContext;
@Stateless
public class HelloWorldBean implements HelloWorld
{
@AroundInvoke
public

Object myInterceptor(InvocationContext ctx) throws Exception {
System.out.println("Ahem...");
return ctx.proceed();
}
public void sayHello()
{ System.out.println("Hello World!"); }
}

Слайд 19

Interceptor Classes
External interceptor classes can be created to abstract the behavior

of interceptors and to define multiple interceptors for a bean.

// Bean Class
@Stateless
@Interceptor(CheckUserInterceptor.class)
@Interceptor(LogActivity.class)
public class HelloWorldBean implements HelloWorld
{… }

// Interceptor Class
public class CheckUserInterceptor {
@AroundInvoke
public Object checkId(InvocationContext ctx) {…}
}

Слайд 20

Summary
In this lesson, you should have learned how to:
Describe session beans
Create

stateless and stateful session beans by using annotations
Understand the passivation and activation of stateful session beans
Use interceptor methods and classes

Creating Session Beans

Содержание

ObjectivesAfter completing this lesson, you should be able to:Describe session beansCreate

What Is a Session Bean?A session bean is a type of

Stateless Versus Stateful Session BeansThere are two types of session beans:Stateless

Life Cycle of a Stateless Session BeanReadyCreationDoes not existDestructionMethod

Creating a Stateless Session BeanTo create a stateless session bean:Define the

Define the Stateless Session Bean// HelloWorldBean.javapackage helloworld.ejbimport javax.ejb.Stateless;@Stateless(name="HelloWorld")public class HelloWorldBean implements

Create the Remote and Local Interfaces// HelloWorld.javapackage helloworld.ejbimport javax.ejb.Remote;@Remotepublic interface HelloWorld

Create a Test Client for the SLSB// HelloWorldClient.javaimport helloworld.ejb;import javax.naming.Context;import javax.naming.InitialContext;import

Life Cycle of a Stateful Session BeanReadyCreationPassiveActivationPassivationDoes not existDestructionReady (in TX)Commit/rollbackTX

Passivation and Activation ConceptsPassivation and activation are stages in a session

Creating a Stateful Session Bean To create a stateful session bean:Define

Define the Stateful Session Bean// CartBean.javapackage cart.ejbimport javax.ejb.Stateful;…@Stateful(name="Cart")public class CartBean implements

Create the Remote and Local Interfaces// Cart.javapackage cart.ejbimport javax.ejb.Remote;…@Remotepublic interface Cart

Create a Test Client for the SFSB// CartClient.javaimport …public class CartClient

Interceptor Methods and ClassesEJB 3.0 introduces the ability to create custom

Interceptor Methodimport javax.ejb.Stateless;import javax.ejb.AroundInvoke;import javax.ejb.InvocationContext;@Statelesspublic class HelloWorldBean implements HelloWorld{ @AroundInvoke public

Interceptor ClassesExternal interceptor classes can be created to abstract the behavior

SummaryIn this lesson, you should have learned how to:Describe session beansCreate

Похожие презентации