Enterprise Java Beans
PA165
30. 10. 2012
Petr Adámek

Content
˂EJB Introduction and history
˂EJB Components
˂Stateless Session Bean
˂Statefull Session Bean
˂Singleton Session Bean
˂Message Driven Bean
˂AOP / Interceptors
˂Transaction Management
˂Security Management
˂EJB Time Service
˂CDI
˂EJB versus Spring
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EJB Introduction
˂Enterprise JavaBeans (EJB) is a managed, server-side component architecture for modular
construction of enterprise applications.
˂
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EJB History
˂EJB 1.0 (1998)
˂EJB 1.1 (1999), J2EE 1.2
˂XML descriptors, role driven security, Entity EJB
˂EJB 2.0 (2001), JSR 19, J2EE 1.3
˂Message-Driven Beans, local interfaces, RMI-IIOP
˂EJB 2.1 (2003), JSR 153, J2EE 1.4
˂Web services support, Timer Service, aggregation support in EJB-QL
˂EJB 3.0 (2006), JSR 220, Java EE 5
˂Simpler development, Annotations, POJO components, convention-over-configuration, JPA, Entity
Beans and home interfaces dropped.
˂EJB 3.1 (2009), JSR 318, Java EE 6
˂Singletons, Local view, war packaging, EJB Lite, Portable JNDI names, App init and shutdown
events, Time Service enhancements, @Asynchronous, embeddable EJB
˂
˂
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EJB Container
˂Provides services to components
˂Lifecycle control
˂Dependency injection
˂Transaction management
˂Remote access
˂Access control
˂
˂You need application server with EJB Container
˂Java EE 6 Full Profile
˂Java EE 6 Web Profile (only EJB Lite)
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EJB Components
˂Entity Beans
˂Deprecated in EJB 3.0, replaced with JPA
˂Session Beans
˂Stateless
˂Statefull
˂Singleton
˂Message-Driven Beans
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AOP / Interceptors
˂public class MyInterceptor {
˂  @AroundInvoke
  public Object methodName(InvocationContext
    invocationContext)throws Exception {

˂    // Do, what we need…
    Object result =  invocationContext.proceed();
    // Do, what we need…
    return result;
}
˂
˂@Interceptors({MyInterceptor.class})
˂// This annotation can be used on whole class or
˂// on only some methods
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Transaction Management
˂Transactions are controlled by JTA
˂Global transactions
˂Distributed transactions
˂Container Managed Transactions
˂Declarative approach
˂Controlled with annotations
˂Bean Managed Transactions
˂Imperative approach
˂Controlled with code
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Transaction Management
˂Transaction attributes
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˂
TransactionAttributeType
Transaction already in progress
No transaction in progress
MANDATORY
Current transaction is used.
Exception is thrown.
NEVER
Exception is thrown.
No transaction is used.
NOT_SUPPORTED
Current transaction is suspended
No transaction is used.
REQUIRED
Current transaction is used.
New transaction is created.
REQUIRES_NEW
Current transaction is suspended, new transaction is created.
New transaction is created.
SUPPORTS
Current transaction is used.
No transaction is used.

Security Management
˂javax.annotation.security
˂@DeclareRoles
˂@DenyAll
˂@PermitAll
˂@RolesAllowed
˂@RunAs
˂
˂http://www.packtpub.com/article/hands-on-tutorial-ejb-security
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Timer Service
˂@Schedule
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CDI
˂Commons and Dependency Injection
˂More flexible than standard Dependency Injection on Web, EJB, or JSF components (Qualifiers,
Stereotypes, etc.)
˂Simplifies integration
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EJB 3.1 versus Spring: General
˂Java EE 6 /  EJB 3.1
˂Platform
˂JCP Standard
˂Both free and commercial implementation available
˂Standard approaches for common problems
˂More convention-over-configuration principle, simpler configuration
˂EJB Container is requires
˂
˂Spring
˂Framework
˂Proprietary
˂Free, Open Source
˂Less invasive, you can choose your favorite approach for each problem
˂More flexible, but more complicated configuration
˂Just Spring IoC container required (part of framework)
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Spring je ve skutecnosti IoC + AOP kontejner