We can see that when we want to use the Dom4j to parse XML , we should import org.dom4j.*
At the same time ,that to parse XML by DOM ,we should import org.w3c.dom.*
The conclusion is that DOM and Dom4j is different and located in different jar.The DOM belongs to w3c and the Dom4j belongs to dom4j.
The DOM parser will load the whole xml file and create a DOM tree, it will cost much space of memoty and lead to memory leak.
So the DOM parser will be easily to modify the xml file.
The SAX parser will load the single node and cost little space of memory, while it's not so easy to modify the xml file.
The DOM parser belongs to JAXP(Java API for XML processing), and it is part of JavaSE includes the following parts:
org.w3c.dom: provide the DOM parser to parse XML standard interface
org.xml.sax: provide the SAX parser to parse XML standard interface
javax.xml: provide the class of parsing XML file
But how do we parse XML by DOM?
//1.get the DocumentBuilderFactory by its static method
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
//2.get the DocumentBuilder by DocumentBuilderFactory's newDocumentBuilder() method
DocumentBuilder builder = factory.newDocumentBuilder();
//3.get the Document object by DocumentBuilder
Document document = DocumentBuilder.parse("book.xml");
//4.to handle the document further ,we can use getElementByTagName("") method get the NodeList
NodeList list = document.getElementByTagName("");
//5.get the single specific node
Node node = list.item(0);
//6.print the node's text content
System.out.println(node.getTextContent());
To improve the effeciency of using DOM to parse XML , write a util is not a bad idea,isn't it?
public class DOMUtils{
public static Document getDocument(String path){
return DocumentBuilderFactory.newInstance().newDocumentBuilder().parse(path);
}
public static Document getDocument(File file){
return DocumentBuilderFactory.newInstance().newDocumentBuilder().parse(path);
}
public void writeXml2File(Document document,String path){
TransformerFactory.newInstance().newTransformer.transform(new DOMSource(document),new StreamResult(path));
}
}
To append an element to a specific element by DOM , we can use these code:
//1.create an element first
Element element = document.createElement("element's name");
//2.set the element's text content
element.setTextContent("element's content text");
//3.set the element as the child element and append this child element to the parent element.
parentElement.appendChild(element);