What is EJB3?
EJB3 (Enterprise Java Bean 3.0) provides the core component model for Java EE 5 applications. An EJB3 bean is a managed component that is automatically wired to take advantage of all services the Java EE 5 server container provides, such as transaction, security, persistence, naming, dependency injection, etc.
Are EJBS obsolete?
EJB is still there and growing up. There are many new features (SOAP/RESTful webservice, JPA entities, JAXB…)
How do EJBS work?
An EJB container is a run-time container for beans that are deployed to an application server. The container is automatically created when the application server starts up, and serves as an interface between a bean and run-time services such as: Life-cycle management. Code generation.
What is the difference between EJB 2.0 and EJB3 0?
EJB 2.0 deploys entity beans for accessing database. EJB 3.0 has Java Persistence API to access data which is generalized to address issues of portability. EJB 3.0 performs better because it uses POJOs along with metadata annotation, a new introduction.
What are the types of enterprise bean?
There are three types of enterprise beans, entity beans, session beans, and message-driven beans. All beans reside in Enterprise JavaBeans (EJB) containers, which provide an interface between the beans and the application server on which they reside.
Is Java Beans still used?
Well, EJB is certainly alive and very well in Java Persistence Architecture (JPA). JPA is a subset of the EJB3 standard.
What is javax EJB EJBException?
javax.ejb The EJBException is thrown to report that the invoked business method or callback method could not be completed because of an unexpected error (e.g. the instance failed to open a database connection).
What classes are required for EJB 3.0 entity?
EJB 3.0 does not require component and home interfaces. The entity bean class may implement a business interface. The EntityManager class is used to create, find, and update an entity EJB. In EJB 3.0, deployment descriptors are not required and are replaced with metadata annotations.
What is difference between Java and J2EE?
Core Java is used for developing a desktop based application while J2ee is used for Enterprise development. Core java is a programming language used to develop general java application whereas J2ee is a computing platform which consists of core java with a powerful set of libraries.
What are the four parts of J2EE?
The four J2EE application components are: Client tier, Web tier, business tier and enterprise information system (EIS) tier.
What is difference between POJO’s and EJB?
ejb. EntityBean { … } is not a POJO class….POJO vs Java Bean.
| POJO | Java Bean |
|---|---|
| It can implement Serializable interface. | It should implement serializable interface. |
| Fields can be accessed by their names. | Fields are accessed only by getters and setters. |
| Fields can have any visibility. | Fields have only private visibility. |
What is the difference between session bean and entity bean?
This is a summary of the differences between entity and session beans….Session beans and entity beans compared.
| Session bean | Entity bean |
|---|---|
| Typically, persists only for the life of the conversation with the client. (However, may choose to save information.) | Persists beyond the life of a client instance. Persistence can be container-managed or bean-managed. |
How do we handle error in EJB?
setRollBackOnly() method. EJB Container does not wrap the exception in case of Application Exception. When System Exception occurs, EJB container intercepts the exception, rollbacks the transaction and start the clean up tasks. It wraps the exception into RemoteException and throws it to the client.
What is EJB exception in Java?
The EJBException is thrown to report that the invoked business method or callback method could not be completed because of an unexpected error (e.g. the instance failed to open a database connection).
Why do we need JavaBeans?
Why use JavaBean? According to Java white paper, it is a reusable software component. A bean encapsulates many objects into one object so that we can access this object from multiple places. Moreover, it provides easy maintenance.
Which is an EJB application exception?
An application exception is a checked exception that is either defined by the bean developer and does not extend a RemoteException, or is predefined in the javax. ejb package (that is, CreateException, DuplicateKeyException, FinderException, ObjectNotFoundException, or RemoveException).
What is EJB and why it is used?
EJB is a server-side software component that encapsulates business logic of an application. An EJB web container provides a runtime environment for web related software components, including computer security, Java servlet lifecycle management, transaction processing, and other web services.
What is EJB in Java with example?
EJB (Enterprise Java Bean) is used to develop scalable, robust and secured enterprise applications in java. Unlike RMI, middleware services such as security, transaction management etc. are provided by EJB Container to all EJB applications. The current version of EJB is EJB 3.2.