Java Integration

1. Create an Eclipse Project named DOM Parser. 

2. Create 3 new classes inside the package com.javatweaks.dom

    Items.java

    DOMCreator.java (with main)

    createXMLDOM.java 

3. Let us define the createXMLDOM class first. 

4. We will create a method createXMLDoc() that will return a Document object. Note we will use the package com.w3c.dom for our application. 

5. We have to create 3 objects sequentially. 

 DocumentBuilderFactory to create a factory object

 DocumentBuilder to create a builder object

 Document to create the XML document

We will do that by adding the below lines. 

DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();

DocumentBuilder builder = factory.newDocumentBuilder();

Document doc = builder.newDocument();

6. Now we will have to define the root element for the XML document that we created.  For that we will use the Element object from com.w3c.dom

Element rootElement = doc.createElement("items");

7. Now that we have created the root element, we have to attach the same to the Document. For that 

doc.appendChild(rootElement);

The code will be like.

package com.javatweaks.dom;

import javax.xml.parsers.DocumentBuilder;

import javax.xml.parsers.DocumentBuilderFactory;

import javax.xml.parsers.ParserConfigurationException;

import org.w3c.dom.Document;

import org.w3c.dom.Element;

public class createXMLDOM {

    public Document createXMLDOC() throws ParserConfigurationException {

        DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();

        DocumentBuilder builder = factory.newDocumentBuilder();

        Document doc = builder.newDocument();

        Element rootElement = doc.createElement("items");

        doc.appendChild(rootElement);

        return doc;

    }

}

7. Now let us use this class in the main method. Goto the class DOMCreator and create an instance for the class createXMLDOM

8. We cannot print the document. We have to do something here. Create a Node object and use getFirstChild() method to access node. 

Below is the code. 

package com.javatweaks.dom;

import javax.xml.parsers.ParserConfigurationException;

import org.w3c.dom.Document;

import org.w3c.dom.Node;

public class DOMCreator {

    public static void main(String[] args) throws ParserConfigurationException {

        createXMLDOM dom = new createXMLDOM();

        Document doc = dom.createXMLDOC();

        Node root = doc.getFirstChild();

        System.out.println(root.getNodeName());

    }

}

Execute the code and print the same. It will just print the node name as item

Now let us add data elements and attributes with DOM

9. For reading the XML let us not write anothe parser. Let use use our previouse project and import it to this project and reuse the same. Here is the link

10. Use the below lines to do so. 

    String filename = "C:\\Users\\xxx\\Documents\\Java_XML\\items.xml";

    SAXItemsHandler saxHandler = new SAXItemsHandler();

    List<Items> data = saxHandler.readDataFromXML(filename);

11. Update the createXMLDOC() method to get List<Items> as parameter like createXMLDOC(List<Items> data)

12. In the main method call the createXMLDOC() with parameter like this. Document doc = dom.createXMLDOC(data);

13. create a foreach loop to iterate through items in the mothod createXMLDOC(). 

        for (Items item : data) {

            Element itemElement = doc.createElement("item");

            rootElement.appendChild(itemElement);

            String idString = Integer.toString(item.getId());

            rootElement.setAttribute(Items.ID, idString);

        }

14. Now let us go back to the main method and print them. In order to do that, we have to go through this hierarchy. 

    Get the root node > create a NodeList object to access the item and Node to access each item. 

        NodeList nodes = root.getChildNodes();

        for (int i = 0; i < nodes.getLength(); i++) {

                Node child = nodes.item(i);

                System.out.println(child.getNodeName());

        }

Now we have gone till the attribute. Now let us add data in the form of more child items. Let us refactor the code a little. 

15. Select the below two lines > Right click > Refactor > Extract Method. 

Element itemElement = doc.createElement("item");

rootElement.appendChild(itemElement);