Reading the xml using JDOM

JDOM represents an XML document as an instance of the org.jdom.Document class. The Document class is a lightweight class that can hold a DocType, multiple ProcessingInstruction objects, a root Element, and Comment objects. You can construct a Document from scratch without needing a factory:

Document doc = new Document(new Element("rootElement")); 

But in case of JDOM there are multiple ways of building Document. Egs. :

Builders

SAXBuilder builder = new SAXBuilder();
Document doc = builder.build(url);

You can build documents from any data source using builder classes found in the org.jdom.input package. Currently there are two builders, SAXBuilder and DOMBuilder. SAXBuilder uses a SAX parser behind the scenes to build the Document from the file; the SAXBuilder listens for the SAX events and builds a corresponding Document in memory. That approach is very fast (basically as fast as SAX), and it is the approach we recommend. DOMBuilder is another alternative that builds a JDOM Document from an existing org.w3c.dom.Document object. It allows JDOM to interface easily with tools that construct DOM trees.
Builders are also being developed that construct JDOM Document objects from SQL queries, LDAP queries, and other data formats. So, once in memory, documents are not tied to their build tool.
Examples with SAX builder:
1. String source

String data =
                "<root>" +
                "<Companyname>" +
                "<Employee name=\"Girish\" Age=\"25\">Developer</Employee>" +
                "</Companyname>" +
                "<Companyname>" +
                "<Employee name=\"Komal\" Age=\"25\">Administrator</Employee>" +
                "</Companyname>" +
                "</root>";
        SAXBuilder builder = new SAXBuilder();
        Document document = builder.build(new ByteArrayInputStream(data.getBytes()));

2.From URL

SAXBuilder builder = new SAXBuilder();
Document doc = builder.build(url);

Validation
The SAXBuilder and DOMBuilder constructors let the user specify if validation should be turned on, as well as which parser class should perform the actual parsing duties.

public SAXBuilder(String parserClass, boolean validation);
public DOMBuilder(String adapterClass, boolean validation);

The defaults are to use Apache's open source Xerces parser and to turn off validation. Notice that the DOMBuilder doesn't take a parserClass but rather an adapterClass. That is because not all DOM parsers have the same API. To still allow user-pluggable parsers, JDOM uses an adapter class that has a common API for all DOM parsers. Adapters have been written for all the popular DOM parsers, including Apache's Xerces, Crimson, IBM's XML4J, Sun's Project X, and Oracle's parsers V1 and V2. Each one implements that standard interface by making the right method calls on the backend parser. That works somewhat similarly to JAXP (Resources) except it supports newer parsers that JAXP does not yet support.