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Java XML

Java XML Tutorial

Java XML Home

  1. XML (Extensible Markup Language) is text based language generally used for communication between different apps
    1. Standard means to transport and store data
  2. Java has rich set of libraries to parse, modify or inquire XML docs
  3. Topics
    1. Basic XML concepts
    2. Usage of Java based XML parsers
  4. Pre-requisites
    1. Basic concepts

Java XML Overview

What is XML?

  1. It is text based language designed to store and transport data in plain text format

  2. Salient features

    1. XML is a markup language
    2. XML is tag based language like HTML
    3. XML tags are not predefined like HTML
    4. We can define own tags (extensible)
    5. XML tags are self-descriptive
    6. XML is W3C reccomendation for data storage and data transfer

  3. Example:

     <?xml version="1.0"?>
 <Class>
 	<Name>First</Name>
 	<Sections>
 		<Section>
 			<Name>A</Name>
 			<Students>
 				<Student>Rohan</Student>
 				<Student>Mohan</Student>
 				<Student>Sohan</Student>
 				<Student>Lalit</Student>
 				<Student>Vinay</Student>
 			</Students>
 		</Section>

 		<Section>
 			<Name>B</Name>
 			<Students>
 				<Student>Robert</Student>
 				<Student>Julie</Student>
 				<Student>Kalie</Student>
 				<Student>Michael</Student>
 			</Students>
 		</Section>
 	</Sections>
 </Class>

Advantages

  1. Technology agnostic: It is plain text, technology independent
    1. Can be used by any technology for data storage
  2. Human readable
  3. Extensible: Custom tags can be created and used easily
  4. Allow Validation: XSD, DTD validation

Disadvantages

  1. Redundant Syntax: Usually contains lot of repititive terms
  2. Verbose: file size increases transmission and storage costs

Java XML Parsers

  1. Parsing: Going through XML document to access or modify data

What is XML Parser?

  1. Types of parsers commonly used to parse XML documents:
    1. Dom Parser: Parses by loading complete contents of document into complete hierarchical tree in memory
    2. SAX Parser: Parses XML document on event-based triggers
      1. Does not load complete document into memory
    3. JDOM Parser: Similar to DOM parser but in easier way
    4. StAX Parser: Similar to SAX parser but in more efficient way
    5. XPath Parser: Parsing based on expression and is usually used in conjunction with XSLT
    6. DOM4J Parser: Parse XML, XPath and XSLT using Java Collections framework
      1. Supports DOM, SAX and JAXP
    7. JAXB and XSLT APIs are available to handle XML parsing in object-oriented way

Java DOM Parser

  1. DOM is official recommendation of W3C
    1. Defines an interface that enables programs to access and update style, structure, and contents of XML docs
    2. XML parsers that support DOM implement the interface

When to Use?

  1. Need to know a log about the structure of the document
  2. Need to move parts of XML document around
    1. Sorting certain elements
    2. ...
  3. Need to use information in XML document more than once

What You Get?

  1. A tree structure that contains all elements of your document. DOM has functions which can be used to examine contents and structure of document.

Advantages

  1. Java code written for one DOM-compliant parser should run on any other DOM-compliant parser without having to do any modifications

DOM Interfaces

  1. Different DOM interfaces:
    1. Node: base datatype of DOM
    2. Element: Vast majority of objects
    3. Attr: Represents attribute of element
    4. Text: Actual content of element or attr
    5. Document: Represents entire XML document
      1. Referred to as DOM tree

Common DOM Methods

  1. Methods:
    1. Document.getDocumentElement() - Returns root element of document
    2. Node.getFirstChild() - Returns first child of given Node
    3. Node.getLastChild() - Returns last child of given Node
    4. Node.getPreviousSibling() - Methods return previous sibling of given Node
    5. Node.getAttribute(attrName) - For given node, returns attribute with requested name

Java DOM Parser

Parse XML Document

Steps to Using JDOM

  1. Steps
    1. Import XML-related packages
    2. Construct a SAXBuilder
    3. Construct a Document from a file or stream
    4. Extract the root element
    5. Examine attributes
    6. Examine sub-elements
Import XML-related packages
	import org.w3c.dom.*;
	import javax.xml.parsers.*;
	import java.io.*;
Creation of a DocumentBuilder
	DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
	DocumentBuilder builder = factory.newDocumentBuilder();
Creation of a Document from a file or stream
	StringBuilder xmlStringBuilder = new StringBuilder();
	xmlStringBuilder.append("<?xml version="
Extract the root element
Examine attributes
Examine sub-elements

Demo Example

DomParserDemo.java

Query XML Document

Create XML Document

Modify XML Document

Java SAX Parser

Java SAX Parser

Parse XML Document

Query XML Document

Create XML Document

Modify XML Document

JDOM XML Parser

JDOM XML Parser

Parse XML Document

Query XML Document

Create XML Document

Modify XML Document

Java StAX Parser

Java StAX Parser

Parse XML Document

Query XML Document

Create XML Document

Modify XML Document

Java XPath Parser

Java XPath Parser

Parse XML Document

Query XML Document

Create XML Document

Modify XML Document

Java DOM4J Parser

Java DOM4J Parser

Parse XML Document

Query XML Document

Create XML Document

Modify XML Document

Java XML Useful Resources

Java XML - Questions and Answers

Java XML - Quick Guide

Java XML - Useful Resources

Java XML - Discussion