10 XML Interview questions and answers for Java Programmer

XML Interview questions are very popular in various programming job
interviews, including Java interviews for web developer.
XML is a matured technology and often used as standard for transporting data
from one platform other. XML Interview
questions contains questions from various XML technologies like XSLT which
is used to transform XML files, XPATH, XQuery and fundamentals
of XML e.g. DTD or Schema. In this
article we will see 10 frequently asked XML
Interview questions and answers from above topics. These questions are
mostly asked in various Java interviews but they are equally useful in other programming interviews  like C, C++, Scala or any other programming
language. Since XML is not tied with any programming language and like SQL its
one of the desired skill in programmer, it make sense to practice some XML
questions before appearing in any technical job interview

XML Interview Questions and Answers

Here is my list of some common and frequently asked Interview questions
on XML technologies.  Questions on this
list is not very tough but touches some important areas of XML technologies
e.g. DTD, XML Schema, XSLT transformations, XPATH evaluation, XML binding,
XML parsers and fundamentals of XML e.g. namespace, validation, attribute,
elements etc.

Question 1:
What is XML ?

Answer : XML stands for Extensible Markup language which means you can
extend XML based upon your needs. You can define custom tags like , etc in XML
easily as opposed to other mark-up language like HTML where you need to work
with predefined tags e.g.

and you can not use user defined
tag. Though structure of XML can be standardize by making use of DTD and XML
Schema. XML is mostly used to transfer data from one system to another e.g.
between client and server in enterprise applications.

Question
2: Difference between DTD and XML Schema?

Answer : There are couple of differences between DTD and XML Schema e.g.
DTD is not written using XML while XML schema are xml documents in itself,
which means existing XML tools like XML parsers can be used to
work with XML schema. Also XML schema is designed after DTD and it offer more
types to map different types of data in XML documents. On the other hand DTD
stands for Document Type definition and was a legacy way to define structure of
XML documents.

Question
3: What is XPath ?

Answer : XPath is an XML technology which is used to retrieve element
from XML documents. Since XML documents are structured, XPath expression can be
used to locate and retrieve elements, attributes or value from XML files. XPath
is similar to SQL in terms of retrieving data from XML but it has it's own
syntax and rules. See here to know more about How to use XPath to retrieve data from
XML documents.

Question
4: What is XSLT?

Answer : XSLT is another popular XML technology to transform one XML file
to other XML, HTML or any other format. XSLT is like a language which specifies
its own syntax, functions and operator to transform XML documents. Usually
transformation is done by XSLT Engine which reads instruction written using
XSLT syntax in XML style sheets or XSL files. XSLT also makes extensive use of recursion to perform
transformation. One of the popular example of using XSLT is for displaying data
present in XML files as HTML pages. XSLT is also very handy to transforming one
XML file into another XML document.

Question
5: What is element and attribute in XML?

Answer : This can be best explained by an example. let's see a simple XML
snippet

  id="123">

     
6758.T

     
2300

 

In this sample XML id is an attribute of element.
Here , and are also
other elements but they don't have any attribute.

Question
6: What is meaning of well formed XML ?

Answer : Another interesting XML
interview question which most appeared in telephonic interviews. A well
formed XML means an XML document which is syntactically correct e.g. it
has a root element, all open tags are closed properly, attributes are in quotes
etc.  If an XML is not well formed, it
may not be processed and parsed correctly by various XML parsers.

Question
7: What is XML namespace? Why it's important?

Answer : XML namespace are similar to package in Java and used to
provide a way to avoid conflict between two xml tags of same name but different
sources. XML namespace is defined using xmlns attribute at top of the XML
document and has following syntax 
xmlns:prefix="URI". later that prefix is used along with
actual tag in XML documents. Here is an example of using XML namespace :

xmlns:inst="http://instruments.com/inst"

 

      837363223

   

Question
8: Difference between DOM and SAX parser ?

Answer : This is another very popular XML interview question, not just in
XML world but also on Java world. Main difference between DOM and SAX parser is
the way they parse XML documents. DOM creates an in memory tree representation
of XML documents during parsing while SAX is a event driven parser. See Difference between DOM and SAX parser
for more detailed answer of this question.

Question
9: What is a CDATA section in XML?

Answer : I like this XML Interview questions for its simplicity and
importance, yet many programmer doesn't know much about it. CDATA stands for character
data and has special instruction for XML parsers. Since XML parser parse all
text in XML document e.g. This is name of person  here even though value of tag will be
parsed because it may contain XML tags e.g. First
Name. CDATA
section is not parsed by XML parser. CDATA section starts with " and
finishes with "]]>".

Question
10: What is XML data Binding in Java?

Answer : XML binding in Java refers to creating Java classes and object
from XML documents and then modifying XML documents using
Java programming language. JAXB , Java API for XML binding provides convenient
way to bind XML documents with Java objects. Other alternatives for XML binding
is using open source library e.g. XML Beans. One of the biggest advantage of
XML binding in Java is to leverage Java programming capability to create and
modify XML documents.

This list of XML Interview questions and answers are collected
from programmers but useful to anyone who is working in XML technologies.
Important of XML technologies like XPath, XSLT, XQuery is only
going to increase because of platform independent nature of XML and it's
popularity of transmitting data over cross platform. Though XML has
disadvantage like verbosity and size but its highly useful in web services and
transmitting data from one system to other where bandwidth and speed is of
secondary concern.

Source:http://javarevisited.blogspot.com/2013/01/10-xml-interview-questions-and-answers.html