Sunday, May 20, 2018

EJB Interview questions

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EJB Interview questions

What is EJB

Enterprise JavaBeans.

What is EJB container

A container that implements the EJB component contract of the J2EE architecture. This contract specifies a run time environment for enterprise beans that includes security, concurrency, life-cycle management, transactions, deployment, naming, and other services. An EJB container is provided by an EJB or J2EE server.

What is EJB container provider

A vendor that supplies an EJB container.

What is EJB context

A vendor that supplies an EJB container. An object that allows an enterprise bean to invoke services provided by the container and to obtain the information about the caller of a client-invoked method.

What is EJB home object

An object that provides the life-cycle operations (create, remove, find) for an enterprise bean. The class for the EJB home object is generated by the container’s deployment tools. The EJB home object implements the enterprise bean’s home interface. The client references an EJB home object to perform life-cycle operations on an EJB object. The client uses JNDI to locate an EJB home object.

What is EJB JAR file

A JAR archive that contains an EJB module.

What is EJB module

A deploy able unit that consists of one or more enterprise beans and an EJB deployment descriptor.

What is EJB object

An object whose class implements the enterprise bean’s remote interface. A client never references an enterprise bean instance directly; a client always references an EJB object. The class of an EJB object is generated by a container’s deployment tools.

What is EJB server

Software that provides services to an EJB container. For example, an EJB container typically relies on a transaction manager that is part of the EJB server to perform the two-phase commit across all the participating resource managers. The J2EE architecture assumes that an EJB container is hosted by an EJB server from the same vendor, so it does not specify the contract between these two entities. An EJB server can host one or more EJB containers.

What is EJB server provider

A vendor that supplies an EJB server.

What is element

A unit of XML data, delimited by tags. An XML element can enclose other elements.

What is empty tag

A tag that does not enclose any content

What is enterprise bean

A J2EE component that implements a business task or business entity and is hosted by an EJB container; either an entity bean, a session bean, or a message-driven bean.

What is enterprise bean provider

An application developer who produces enterprise bean classes, remote and home interfaces, and deployment descriptor files, and packages them in an EJB JAR file.

What is enterprise information system

The applications that constitute an enterprise’s existing system for handling company wide information. These applications provide an information infrastructure for an enterprise. An enterprise information system offers a well-defined set of services to its clients. These services are exposed to clients as local or remote interfaces or both. Examples of enterprise information systems include enterprise resource planning systems, mainframe transaction processing systems, and legacy database

What is enterprise information system resource

An entity that provides enterprise information system-specific functionality to its clients. Examples are a record or set of records in a database system, a business object in an enterprise resource planning system, and a transaction program in a transaction processing system.

What is Enterprise JavaBeans (EJB)

A component architecture for the development and deployment of object-oriented, distributed, enterprise-level applications. Applications written using the Enterprise JavaBeans architecture are scalable, transactional, and secure.

What is Enterprise JavaBeans Query Language (EJB QL)

Defines the queries for the finder and select methods of an entity bean having container-managed
persistence. A subset of SQL92, EJB QL has extensions that allow navigation over the relationships defined in an entity bean’s abstract schema.

What is an entity

A distinct, individual item that can be included in an XML document by referencing it. Such an entity reference can name an entity as small as a character (for example, <, which references the less-than symbol or left angle bracket, <). An entity reference can also reference an entire document, an external entity, or a collection of DTD definitions.

What is entity bean

An enterprise bean that represents persistent data maintained in a database. An entity bean can manage its own persistence or can delegate this function to its container. An entity bean is identified by a primary key. If the container in which an entity bean is hosted crashes, the entity bean, its primary key, and any remote references survive the crash.

What is entity reference

A reference to an entity that is substituted for the reference when the XML document is parsed. It can reference a predefined entity such as < or reference one that is defined in the DTD. In the XML data, the reference could be to an entity that is defined in the local subset of the DTD or to an external XML file (an external entity). The DTD can also carve out a segment of DTD specifications and give it a name so that it can be reused (included) at multiple points in the DTD by defining a parameter entity.

What is error

A SAX parsing error is generally a validation error in other words, it occurs when an XML document is not valid, although it can also occur if the declaration specifies an XML version that the parser cannot handle. See also fatal error, warning.

What is Extensible Markup Language


What is external entity

An entity that exists as an external XML file, which is included in the XML document using an entity

What is external subset

That part of a DTD that is defined by references to external DTD files.

What is fatal error

A fatal error occurs in the SAX parser when a document is not well formed or otherwise cannot be processed. See also error, warning.

What is filter

An object that can transform the header or content (or both) of a request or response. Filters differ from Web components in that they usually do not themselves create responses but rather modify or adapt the requests for a resource, and modify or adapt responses from a resource. A filter should not have any dependencies on a Web resource for which it is acting as a filter so that it can be composable with more than one type of Web resource.

What is filter chain

A concatenation of XSLT transformations in which the output of one transformation becomes the input of thenext.

What is finder method

A method defined in the home interface and invoked by a client to locate an entity bean.

What is form-based authentication

An authentication mechanism in which a Web container provides an application-specific form for logging in. This form of authentication uses Base64 encoding and can expose user names and passwords unless all connections are over SSL.

What is general entity

An entity that is referenced as part of an XML document’s content, as distinct from a parameter
entity, which is referenced in the DTD. A general entity can be a parsed entity or an unparsed entity.

What is group

An authenticated set of users classified by common traits such as job title or customer profile. Groups
are also associated with a set of roles, and every user that is a member of a group inherits all the roles assigned to that group.

What is handle

An object that identifies an enterprise bean. A client can serialize the handle and then later deserialize it to obtain a reference to the enterprise bean.

What is home handle

An object that can be used to obtain a reference to the home interface. A home handle can be serialized and written to stable storage and de serialized to obtain the reference.

What is home interface

One of two interfaces for an enterprise bean. The home interface defines zero or more methods for managing an enterprise bean. The home interface of a session bean defines create and remove methods, whereas the home interface of an entity bean defines create, finder, and remove methods.
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