Sunday, 1 February 2015

EJB(Enterprise java beans) Interview Questions and Answers (Part2)

11. What are the properties of java beans?
The JavaBeans specification defines the following types of bean properties:
? Simple: A bean property with a single value whose changes are independent of changes in any other property.
? Indexed: A bean property that supports a range of values instead of a single value.
? Bound: A bean property for which a change to the property results in a notification being sent to some other bean.
? Constrained: A bean property for which a change to the property results in validation by another bean. The other bean may reject the change if it is not appropriate.

Bean properties can also be classified as follows:
? Writable: A bean property that can be changed:
? ? Standard
? ? Expert
? ? Preferred
? Read Only: A bean property that cannot be changed.
? Hidden: A bean property that can be changed. However, these properties are not disclosed with the BeanInfo class

12. What are/is Enterprise JavaBeans?
Enterprise JavaBeans (EJB) is an API specification for building scalable, distributed, component-based, multi-tier applications. It leverages and extends the JavaBeans component model to provide a rich object-oriented transactional environment for developers building enterprise applications.
Enterprise JavaBeans (EJB) technology is the basis of Java 2 Platform, Enterprise Edition (J2EE). EJB technology provides the scalable architecture for executing business logic in a distributed computing environment. J2EE makes the life of an enterprise developer easier by combining the EJB component architecture with other enterprise technologies to solutions on the Java platform for seamless development and deployment of server side applications.

13. Who is developing the JavaBeans Migration Assistant to ActiveX?
IBM and Taligent, its object oriented technology subsidiary, with support from JavaSoft, are developing a set of conversion conventions, a porting guide and tool that will allow developers to easily convert their Windows ActiveX components into JavaBeans.

14. Why is the JavaBeans Bridge for ActiveX only available on Windows/X86?
Sun's JavaBeans Bridge for ActiveX is platform specific due to the platform specific nature of ActiveX. Currently, ActiveX is essentially a Window/X86 platform specific component architecture.
If Microsoft delivers ActiveX libraries and ActiveX applications on other platforms, Sun will evaluate customer demand and respond accordingly.

15. What is the relation between the InfoBus and RMI?
The InfoBus architecture addresses Beans talking to one in a single JVM not across multiple JVMs; while RMI (Remote Method Invocation) is intended for communication across JVMs (different Java Virtual Machines across the network). As for IIOP, one can envision a JavaBeans component that uses RMI to talk to something on another JVM and then publishes the data on the InfoBus.
Additionally, RMI could be used to allow components in different security classes to communicate within the same JVM.

16. Difference between java Beans and Enterprise Java Beans?
? JavaBeans may be visible or nonvisible at runtime.For example, the visual GUI component may be a button,list box,graphic or a chart.
An EJB is a nonvisual ,remote object.
? JavaBeans are intended to be local to a single process and are primarly intended to run on the client side.Although one can develop server-side JavaBeans,it is far easier to develop them using the EJB specification instead.
EJB's are remotely executable components or business objects that can be deployed only on the server.
? JavaBeans is a component technology to create generic Java components that can be composed together into applets and applications.
Even though EJB is a component technology,it neither builds upon nor extends the original JavaBean specification.
? JavaBeans have an external interface called the properties interface, which allows a builder tool to interpret the functionality of the bean.
EJBs have a dployement descriptor that describes its functionality to an external builder tool or IDE
? JavaBeans may have BeanInfo classes,property editors or customizers

17. Is the InfoBus client side only?
Yes. InfoBus is typically used to communicate among Beans at the client, and it can also be useful for sharing information among components at a single server site. The initial version of InfoBus is not distributed, and is therefore not intended for transmission of data between clients and servers.
A variety of Java communication services, including JDBC, CORBA, and RMI can be used by InfoBus components for access to distributed data. For example, the ESuite Data Access component is a Bean that connects any JDBC compliant data source to the InfoBus. Once the data is on the bus, it can easily be imported by any InfoBus Data Consumer, such as a spreadsheet, chartingcomponent, word processor or data analysis tool.

18. Will the general public have access to the InfoBus API s?
Yes, under the usual terms of the JDK license. The specification and technology preview are available in our products archive.

19. How does the InfoBus relate to JavaBeans?
The InfoBus specification extends JavaBeans by providing a set of enhanced interfaces to share and exchange dynamic data.

20. What is Glasgow?
Glasgow - the code name for add-ins to the JavaBeans specification. It contains following specifications:
? The Extensible Runtime Containment and Services Protocol
? The Drag and Drop Subsystem for the Java Foundation Classes
? The JavaBeans Activation Framework
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