J2EE Interview questions and answers

PART III

61. 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.

62. What is declarative security

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

63. What is delegation

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

restrictions.

64. What is deployer

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

65. What is deployment

The process whereby software is installed into an operational environment.

66. 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.

67. 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.

68. 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.

69. 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).

67. What is document

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

68. 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.

69. 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.

70. 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.

81. 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.

82. 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.

83. What is EJB server provider

A vendor that supplies an EJB server.

83.What is element

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

84. What is empty tag

A tag that does not enclose any content

85. 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.

86. 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.

87. 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.

88. 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 A system, and a transaction program in a transaction processing system.

89. 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.

90. What is Enterprise JavaBeans Query Language (EJB

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.

91. 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.

92. 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.

93. 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.

94. 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.

95. What is Extensible Markup Language

XML.

96. What is external entity

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

reference.

96. What is external subset

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

97. 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.

98. 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.

99. What is filter chain

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

100. What is finder method

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

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