EJB Interview Questions and Answers
Question - 1 : - What are the two important TCP Socket classes?
Answer - 1 : - ServerSocket is used for normal two-way socket communication. Socket class allows us to read and write through the sockets. getInputStream() and getOutputStream() are the two methods available in Socket class.
Question - 2 : - What technologies are included in J2EE?
Answer - 2 : - The main technologies in J2EE are: Enterprise JavaBeansTM (EJBsTM), JavaServer PagesTM (JSPsTM), Java Servlets, the Java Naming and Directory InterfaceTM (JNDITM), the Java Transaction API (JTA), CORBA, and the JDBCTM data access API.
Question - 3 : - What is the difference between EJB and Java beans?
Answer - 3 : - EJB is a specification for J2EE server, not a product; Java beans may be a graphical component in IDE.
Question - 4 : - What is EJB role in J2EE?
Answer - 4 : - EJB technology is the core of J2EE. It enables developers to write reusable and portable server-side business logic for the J2EE platform.
Question - 5 : - Tell me something about Local Interfaces.
Answer - 5 : - EJB was originally designed around remote invocation using the Java Remote Method Invocation (RMI) mechanism, and later extended to support to standard CORBA transport for these calls using RMI/IIOP. This design allowed for maximum flexibility in developing applications without consideration for the deployment scenario, and was a strong feature in support of a goal of component reuse in J2EE. Many developers are using EJBs locally, that is, some or all of their EJB calls are between beans in a single container. With this feedback in mind, the EJB 2.0 expert group has created a local interface mechanism. The local interface may be defined for a bean during development, to allow streamlined calls to the bean if a caller is in the same container. This does not involve the overhead involved with RMI like marshalling etc. This facility will thus improve the performance of applications in which co-location is planned. Local interfaces also provide the foundation for container-managed relationships among entity beans with container-managed persistence.
Question - 6 : - What is Enterprise JavaBeans (EJB) container?
Answer - 6 : - It manages the execution of enterprise beans for J2EE applications.
Enterprise beans and their container run on the J2EE server.
Question - 7 : - What is in-memory replication?
Answer - 7 : - The process by which the contents in the memory of one physical m/c are replicated in all the m/c in the cluster is called in-memory replication.
Question - 8 : - What is Ripple Effect?
Answer - 8 : - The process of propagating the changes in the properties of a server group during runtime to all the associated clones is called Ripple Effect.
Question - 9 : - What is a Clone?
Answer - 9 : - The copies of a server group are called Clones. But unlike a Server Group Clones are associated with a node and are real server process running in that node.
Question - 10 : - What are the types of Scaling
Answer - 10 : - There are two types of scaling: Vertical Scaling and Horizontal Scaling.
Vertical Scaling - When multiple server clones of an application server are defined on the same physical m/c, it is called Vertical Scaling. The objective is to use the processing power of that m/c more efficiently.
Horizontal Scaling - When Clones of an application server are defined on multiple physical m/c, it is called Horizontal Scaling. The objective is to use more than one less powerful m/c more efficiently.