JDOM

1
JDOM

• JDOM itself is not a parser
• it is a wrapper,
• and requires the presence of an underlying parser
  .

2
Installing

• http//www.jdom.org
• Place all of my Java tools under
  c\java\j2sdkee1.3
• Set JAVA_HOMEC\java\jdk1.3
• Run C\java\jdom-1.0gtbuild

3
Batch file

• set JAVA_HOMEc\programfiles\java\jdk1.5.0_05
• set JDOM_HOMEc\program files\java\jdk1.5.0_05\jd
  om-1.0
• set CLASSPATHCLASSPATHJDOM_HOME\build\classe
  sJAVA_HOME\lib\tools.jarJDOM_HOME\lib\xerces
  .jarJDOM_HOME\lib\jaxp.jar

4
Package Structure

• The package structure is as follows-
• org.jdom has the following packages
• org.jdom.input.
• org.jdom.output.
• org.jdom.adapters.
• org.jdom.transform.

5
Parsing a XML document using JDOM

• At the start of your code, include the following
  packages-
• org.jdom.Document.
• org.jdom.Element.
• org.jdom.input.SAXBuilder or DOMBuilder.
• org.jdom.JDOMException.

6
Parsing a XML document using JDOM

• After importing the packages mentioned above.
• A Document object is required to parse a XML
  document.
• A document object is an object representation of
  the XML document you would want to parse.
• Document objects can be obtained either from
  scratch or from an existing XML document.

7
Parsing a XML document using JDOM

• A Document object may be constructed from scratch
  in the following manner.
• If you already have a XML file , then you can do
  the following.

8
Parsing a XML document using JDOM

• Using the document Object obtained from the
  previous slide , get the root element of the
  document.
• Getting the root element using the document
  object can be done in the following manner.
• Element rootelementdoc.getRootElement()

9
Parsing a XML document using JDOM

• Once the root element is obtained, it is very
  easy to traverse the XML document.
• Getting the children of the root element can be
  done using the following manner-
• List childrenroot.getChildren()
• The List used above is nothing but the List class
  that belongs to Java's util package.
• Now one can iterate through the List that is
  obtained above and get individual child elements
  out.

10
Parsing a XML document using JDOM

• If one knows the name of the individual child
  elements, then the method to be used is-
• Element.getName(). This method will return a
  String that will represent the name of the child
  element.
• Once you have the element that you want, you can
  retrieve the value within the tag of the element
  by using the following method-
• Element.getValue()

11
Parsing a XML document using JDOM

• There is also a way of combining the methods
  while checking for a particular element.
• For example-
• Suppose you have a retrieved an element name
  using the method Element.getName(), and you want
  to check if the name equals comment.Then you
  would form your statement is the following
  manner-
• Element.getName().equals(comment)

12
Parsing a XML document using JDOM

• To retrieve attributes within an element tag, one
  can use the following method-
• Element.getAttributeValue(name of the
  attribute)
• One can also retrieve the list of attributes
  within an element tag by using the method-
• Element.getAttributes()
• This method will then return a List of
  attributes, within that element.

13
Parsing a XML document using JDOM

• An element can also have text content. The text
  content can be obtained by using the following
  method-
• Element.getText()
• This method returns a String object , which
  represents the text content of the element.

14
Parsing a XML document using JDOM

• The text content can be changed by using the
  following method-
• Element.setText()
• Parent of an element can be obtained by using
  method.
• Element.getParent()
• The above method will return the parent element
  of a particular element.

15
Example1.java

• import org.jdom.
• public class example1
• public static void main(String args)
• Element root new Element("myRootElement")
• DocType dt new DocType("myRootElement")
• Document doc new Document(root, dt)
• root.setText("This is a root element")
• System.out.println(doc)

16
Adding Elements, Attributes, and Character Data

• import org.jdom.
• public class example2
• public static void main(String args)
• Element root new Element("myRootElement")
• DocType dt new DocType("myRootElement")
• Document doc new Document(root, dt)
• root.setText("This is a root element")
• Element el new Element("el")
• el.setText("This is el!")
• root.addContent(el)
• System.out.println(doc)

17
Emitting the JDOM XML

• use the JDOM XMLOutputter object
• XMLOutputter outputternew XMLOutputter(
  )outputter.output(doc, system.out)
• XMLOutputter(Format format)

18
Example2b.java

• import org.jdom.
• import org.jdom.output.XMLOutputter
• public class example2a
• public static void main(String args)
• Element root new Element("myRootElement")
• DocType dt new DocType("myRootElement")
• Document doc new Document(root, dt)
• root.setText("This is a root element")
• Element el new Element("el")
• el.setText("This is el!")
• root.addContent(el)
• try
• XMLOutputter outputter new XMLOutputter(
  )
• outputter.output(doc, System.out)
• catch (java.io.IOException e)

19
Format

• getCompactFormat()           Returns a new
  Format object that performs whitespace
  normalization, uses the UTF-8 encoding, doesn't
  expand empty elements, includes the declaration
  and encoding, and uses the default entity escape
  strategy.
• See word file

20
Attributes

• Create a new Attribute instance by calling the
  Attribute constructor,
• passing in the name of the attribute and the
  attribute value.
• Then add the Attribute to an Element by calling
  setAttribute.

21
The JDOM Namespace Class

• Create a Namespace object
• Namespace ns Namespace.getNamespace("james",
  "www.jamesbritt.com")
• Use the Namespace to cerate a new Element
• Element el3 new Element("el3", ns)
• Now use that same Namespace object to supply a
  URI, for another Element
• String nsURI ns.getURI()
• Element el4 new Element("el4", nsURI)

22
Adding other nodes types

• Creating a PI, or processing instruction, as
  quite like creating an attribute
• ProcessingInstruction pi new
  ProcessingInstruction("target", someData)
• doc.addContent(pi)
• Comment
• Comment com new Comment("Docs need more
  comments!")
• doc.addContent(com)

23
Saving your JDOM (ex3a)

• Outputter.output() takes two parameters the name
  of the file to write to, and a JDOM Document
  object.
• It creates an output stream using the file name
  to write the XML to the file.

24
Getting the Document as a String (ex4)

• Using saxbuilder to parse XML doc
• XMLOutputter op new XMLOutputter(format)
• String myXml op.outputString(doc)