J2EE Interview Questions with Answers Page II

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What is context attribute?

An object bound into the context associated with a servlet.

What is context root?

A name that gets mapped to the document root of a Web application.

What is conversational state?

The field values of a session bean plus the transitive closure of the objects reachable from the bean's fields. The transitive closure of a bean is

defined in terms of the serialization protocol for the Java programming language, that is, the fields that would be stored by serializing the bean

instance.

What is CORBA?

Common Object Request Broker Architecture. A language-independent distributed object model specified by the OMG.

What is create method?

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

What is credentials?

The information describing the security attributes of a principal.

What is CSS?

Cascading style sheet. A stylesheet used with HTML and XML documents to add a style to all elements marked with a particular tag, for the direction of

browsers or other presentation mechanisms.

What is CTS?

Compatibility test suite. A suite of compatibility tests for verifying that a J2EE product complies with the J2EE platform specification.

What is data?

The contents of an element in an XML stream, generally used when the element does not contain any subelements. When it does, the term content is

generally used. When the only text in an XML structure is contained in simple elements and when elements that have subelements have little or no data

mixed in, then that structure is often thought of as XML data, as opposed to an XML document.

What is DDP?

Document-driven programming. The use of XML to define applications.

What is declaration?

The very first thing in an XML document, which declares it as XML. The minimal declaration is . The declaration is part of the document prolog.

What is declarative security?

Mechanisms used in an application that are expressed in a declarative syntax in a deployment descriptor.

What is delegation?

An act whereby one principal authorizes another principal to use its identity or privileges with some restrictions.

What is deployer?

A person who installs J2EE modules and applications into an operational environment.

What is deployment descriptor?

An XML file provided with each module and J2EE application that describes how they should be deployed. The deployment descriptor directs a deployment

tool to deploy a module or application with specific container options and describes specific configuration requirements that a deployer must resolve.

What is destination?

A JMS administered object that encapsulates the identity of a JMS queue or topic. See point-to-point messaging system, publish/subscribe messaging

system.

What is deployment?

The process whereby software is installed into an operational environment.

What is digest authentication?

An authentication mechanism in which a Web application authenticates itself to a Web server by sending the server a message digest along with its HTTP

request message. The digest is computed by employing a one-way hash algorithm to a concatenation of the HTTP request message and the client's password.

The digest is typically much smaller than the HTTP request and doesn't contain the password.

What is distributed application?

An application made up of distinct components running in separate runtime environments, usually on different platforms connected via a network. Typical

distributed applications are two-tier (client-server), three-tier (client-middleware-server), and multitier (client-multiple middleware-multiple

servers).

What is document?

In general, an XML structure in which one or more elements contains text intermixed with subelements.

What is Document Object Model?

An API for accessing and manipulating XML documents as tree structures. DOM provides platform-neutral, language-neutral interfaces that enables

programs and scripts to dynamically access and modify content and structure in XML documents.

What is document root?

The top-level directory of a WAR. The document root is where JSP pages, client-side classes and archives, and static Web resources are stored.

What is DTD?

Document type definition. An optional part of the XML document prolog, as specified by the XML standard. The DTD specifies constraints on the valid

tags and tag sequences that can be in the document. The DTD has a number of shortcomings, however, and this has led to various schema proposals. For

example, the DTD entry says that the XML element called username contains parsed character data-that is, text alone, with no other structural elements

under it. The DTD includes both the local subset, defined in the current file, and the external subset, which consists of the definitions contained in

external DTD files that are referenced in the local subset using a parameter entity.

What is durable subscription?

In a JMS publish/subscribe messaging system, a subscription that continues to exist whether or not there is a current active subscriber object. If

there is no active subscriber, the JMS provider retains the subscription's messages until they are received by the subscription or until they expire.

What is EAR file?

Enterprise Archive file. A JAR archive that contains a J2EE application.

What is ebXML?

Electronic Business XML. A group of specifications designed to enable enterprises to conduct business through the exchange of XML-based messages. It is

sponsored by OASIS and the United Nations Centre for the Facilitation of Procedures and Practices in Administration, Commerce and Transport

(U.N./CEFACT).

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 runtime 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 deployable 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 companywide 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 systems.

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?

XML.

What is external entity?

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

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 the next.

What is finder method?

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