With this example we are going to demonstrate how to visit recursively the nodes in a DOM Document. We have implemented a method void visitRecursively(Node node), in order to visit a node and its children in the DOM Document. In short, to visit recursively the nodes in a DOM Document you should:
- Obtain a new instance of a DocumentBuilderFactory, that is a factory API that enables applications to obtain a parser that produces DOM object trees from XML documents.
- Set the parser produced so as not to validate documents as they are parsed, using
setValidating(boolean validating)API method of DocumentBuilderFactory, with validating set to false. - Create a new instance of a DocumentBuilder, using
newDocumentBuilder()API method of DocumentBuilderFactory. - Parse the FileInputStream with the content to be parsed, using
parse(InputStream is)API method of DocumentBuilder. This method parses the content of the given InputStream as an XML document and returns a new DOM Document object. - Call
visitRecursively(Node node)method of the example, with the given document as parameter. The method gets the NodeList that contains all children of this node, usinggetChildNodes()API method of Node. For each one of the nodes in the nodeList it gets its name and the value, usinggetNodeName()andgetNodeValue()API methods of Node. Then it begins the same steps for the specified node, to get the children of this node.
Let’s take a look at the code snippet that follows:
package com.javacodegeeks.snippets.core;
import java.io.File;
import java.io.FileInputStream;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import org.w3c.dom.Document;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
public class VisitNodesInDOMDocumentRecursively {
public static void main(String[] args) throws Exception {
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
dbf.setValidating(false);
DocumentBuilder db = dbf.newDocumentBuilder();
Document doc = db.parse(new FileInputStream(new File("in.xml")));
visitRecursively(doc);
}
public static void visitRecursively(Node node) {
// get all child nodes
NodeList list = node.getChildNodes();
for (int i=0; i<list.getLength(); i++) {
// get child node
Node childNode = list.item(i);
System.out.println("Found Node: " + childNode.getNodeName()
+ " - with value: " + childNode.getNodeValue());
// visit child node
visitRecursively(childNode);
}
}
}
Input:
<?xml version="1.0" encoding="UTF-8"?> <rss version="2.0"> <channel> <title>Java Tutorials and Examples</title> <language>en-us</language> <item> <title><![CDATA[Java Tutorials]]></title> <link>http://www.javacodegeeks.com/</link> </item> <item> <title><![CDATA[Java Examples]]></title> <link>http://examples.javacodegeeks.com/</link> </item> </channel> </rss>
Output:
Found Node: rss - with value: null
Found Node: #text - with value:
Found Node: channel - with value: null
Found Node: #text - with value:
Found Node: title - with value: null
Found Node: #text - with value: Java Tutorials and Examples
Found Node: #text - with value:
Found Node: language - with value: null
Found Node: #text - with value: en-us
Found Node: #text - with value:
Found Node: item - with value: null
Found Node: #text - with value:
Found Node: title - with value: null
Found Node: #cdata-section - with value: Java Tutorials
Found Node: #text - with value:
Found Node: link - with value: null
Found Node: #text - with value: http://www.javacodegeeks.com/
Found Node: #text - with value:
Found Node: #text - with value:
Found Node: item - with value: null
Found Node: #text - with value:
Found Node: title - with value: null
Found Node: #cdata-section - with value: Java Examples
Found Node: #text - with value:
Found Node: link - with value: null
Found Node: #text - with value: http://examples.javacodegeeks.com/
Found Node: #text - with value:
Found Node: #text - with value:
Found Node: #text - with value:
This was an example of how to visit recursively the nodes in a DOM Document in Java.
