J2EE Interview questions and answers

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.