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, serverside
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, conventionover-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-overconfiguration
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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