Java JDOM Document Class

Quiz

The Java JDOM Document class represents an XML Document. This class provides various methods to access root element, DocType Definition (DTD), XML namespaces and document level Content objects.

The package org.jdom2 contains the Document class. This class implements the Parent interface and inherits java.lang.Object class. The Document class considers the entire content inside the root element as a single content object.

Using the methods of Document class, we can add, modify, delete Content objects inside an XML Document. Content objects include processing instruction, DocType definition, comments and root element.

Constructors of Document Class

To create a Document object, the Document class provides the following default and parameterized constructors −

Document() − default constructor to create an empty document.
Document(Element rootElement) − creates a new Document object with specified root element.
Document(Element rootElement, DocType docType) − creates a new Document with specified root element and DocType definition.
Document(Element rootElement, DocType docType, java.lang.String baseURI) − creates a new Document with specified root element, DocType definition and BaseURI.
Document(java.util.List<? extends Content> content) − creates a new Document with the Content objects of the supplied list.

Creating an XML Document

Using the above mentioned constructors, we can create XML documents. Here is a Java program that uses a default constructor and a parameterized constructor to create two XML documents.

import org.jdom2.Document;
import org.jdom2.Element;

public class CreateDocument {
   public static void main(String args[]) {
      try {	
    	  
    	 //Using default constructor
	     Document doc1 = new Document();
	     System.out.println(doc1);
	     
	     //Using parameterized constructor
	     Document doc2 = new Document(new Element("book"));
	     System.out.println(doc2);
	     
      } catch (Exception e) { 
    	 e.printStackTrace();
      }
   }
}

The output window displays the two documents created using constructors.

[Document:  No DOCTYPE declaration,  No root element]
[Document:  No DOCTYPE declaration, Root is [Element: <book/>]]

Operations on Root Element

The root element is the main component of any XML document without which we cannot insert any other information of elements inside an XML document. The Document class provides the following methods to perform operations on root element.

Method	Description
getRootElement()	Retrieves root element of an XML document.
detachRootElement()	Detaches root element of an XML document.
hasRootElement()	Checks if there is root inside an XML document.
setRootElement()	Sets or updates the root for an XML document.

Retrieve XML Content

To retrieve document level information from an XML document, the Document class provides the following methods −

Method	Description
getDocType()	Returns the DocType declaration of an XML document.
getBaseURI()	Returns the BaseURI of an XML document.
getContentSize()	Returns the number of content objects inside an XML document.
getContent()	Returns the content objects of the document.
indexOf(Content child)	Returns the index of a Content object.
cloneContent()	Returns the list of content objects of an XML document.
getDescendants()	Returns all the descendants of an XML document.

Add and Delete XML Content

To add and remove Content objects from an XML document, the Document class has these methods −

Method	Description
addContent()	Adds Content objects to an XML document.
removeContent()	Removes content objects from an XML document.

Update XML Content

The Document class provides the following methods to modify content inside an XML document. These methods replaces the content objects if already present, else they insert new content objects.

Method	Description
setBaseURI()	Sets or updates BaseURI of an XML document.
setDocType()	Sets or updates DocType of an XML document.
setContent()	Sets or updates Content objects of an XML document.

Get XML Namespaces

All the namespaces used inside an XML document can be obtained using the following methods of Document class −

Method	Description
getNamespacesInherited()	Returns the list of all inherited XML namespaces that are not introduced in the current XML dcoument.
getNamespacesInScope()	Returns the list of all XML namespaces that are in-scope of this document.
getNamespacesIntroduced()	Returns the list of all XML namespaces that are introduced in the current document.

Get Copies of XML Document

To create more instances of an existing XML document, the Document class provides the following methods −

Method	Description
getDocument()	Returns an instance of the current XML document.
clone()	Returns a deep clone of an XML document.

Other Methods

Following are few more methods of Document class that has different functionality −

Method	Description
toString()	Returns an XML document as a string.
hashCode()	Returns the hash code for an XML document.

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