SCBCD 5 Short Notes

My SCBCD 5 Short Notes..

1)

@PostConstruct
public void initialize( ){ }

@PreDestroy
public void cleanup( ){ }


@PrePassivate
public void cleanup( ){ }

@PostActivate
public void openConnection( ){ }

Access modifier can be  public
                                     protected
                                     default
                                     private
Not static
Not Final
Not throw checked Exceptions
 

@Remove
public void cancel( ){ }

@PostConstruct, @PreDestroy can be used with stateful, stateless session beans
@PrePassivate, @PostActivate, @Remove used with stateful session beans

 2)
Transaction attributes
Reference : EJB 3 in Action

Transaction Attribute	Caller Transaction Exists?	Effect
REQUIRED	No	Container creates a new transaction.
	Yes	Method joins the caller’s transaction.
REQUIRES_NEW	No	Container creates a new transaction.
	Yes	Container creates a new transaction and the caller’s transaction is suspended
SUPPORTS	No	No transaction is used.
	Yes	Method joins the caller’s transaction.
MANDATORY	No	javax.ejb.EJBTransactionRequired-Exception is thrown.
	Yes	Method joins the caller’s transaction.
NOT_SUPPORTED	No	No transaction is used.
	Yes	The caller’s transaction is suspended and the method is called without a transaction
NEVER	No	No transaction is used.
	Yes	javax.ejb.EJBException is thrown

3)

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1. @Entity  
2. public class Project{  
3.     @ManyToMany(mappedBy="projects")  
4.     Set<Employee> emps;  
5. }  
6.   
7. @Entity  
8. public class Employee{  
9.     @ManyToMany(targetEntity=Project.class)  
10.     Collection projects;  
11. }  

@Entity
public class Project{
    @ManyToMany(mappedBy="projects")
    Set<Employee> emps;
}

@Entity
public class Employee{
    @ManyToMany(targetEntity=Project.class)
    Collection projects;
}

If we not use Generics we have to use targetEntity

4 )

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1. @MessageDriven  
2. public class MyMessageBean implements MessageListener{  
3.       
4.     public MyMessageBean(){}  
5.       
6.     public void onMesage(Message message){  
7.           
8.     }  
9. }  

@MessageDriven
public class MyMessageBean implements MessageListener{
    
    public MyMessageBean(){}
    
    public void onMesage(Message message){
        
    }
}

5) EJB Roles

1. Enterprise Bean Provider
2. Application Assembler
3. Deployer
4. EJB Server Provider
5. EJB Container Provider
6. Persistence Provider
7. System Administrator

6)
 @PersistenceUnit
EntityManagerFactory emf;

@PersistenceContext
EntityManager em;

7)Defining a Runtime Exception

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1. @ApplicationException  
2. public class MyException extends java.lang.RuntimeException  

@ApplicationException
public class MyException extends java.lang.RuntimeException

8)  ejb-jar is a contract between ,

           Bean Provider and Application Assembler
           Application Assembler and Deployer