WaysInJavaToParseXML Prof: Dr. Shu-Ching Chen TA: Sheng Guan

Parse XML with Java DOM API How to do this ? The Java DOM API for XML parsing is intended for working with XML as an object graph in memory - a "Document Object Model (DOM)". The parser traverses the XML file and creates the corresponding DOM objects. DOM objects are linked together in a tree structure.

Object model ( DOM Tree)

Steps: 1. Creating A Java DOM XML Parser 2. Parsing XML with a Java DOM Parser 3.Java DOM: Get the Document Object

XML file and corresponding DOM structure <book> <title>Fun Software</title> <author>Jakob Jenkov</author> <ISBN>0123456789</ISBN> </book>

DOM - 3 pieces of XML 1. Elements (sometimes called tags) 2. Attributes 3. The data (also called values) that the elements and attributes describe

Step 1: Creating a Java DOM XML parser Creating a Java DOM XML parser is done using the javax.xml.parsers.DocumentBuilderFactory class. Here is an example: DocumentBuilderFactory builderFactory = DocumentBuilderFactory.newInstance(); DocumentBuilder builder = null; try { builder = builderFactory.newDocumentBuilder(); } catch (ParserConfigurationException e) { e.printStackTrace(); }

Step 2: Parsing an XML file into a DOM tree try { Document document = builder.parse( new FileInputStream("/path/to/your/file.xml")); } catch (SAXException e) { e.printStackTrace(); } catch (IOException e) { }

Step 3: Java DOM: Get the Document Object You are now ready to traverse the Document instance you have received from the DocumentBuilder; The DOM Document object represents an XML document. When you parse an XML file using a Java DOM parser, you get back a Document object.

The DOM Document Element The two most commonly used features of DOM are: 1.Accessing Child Elements of an Element 2.Accessing Attributes of an Element A DOM object contains a lot of different nodes connected in a tree-like structure. At the top is the Document object. The Document object has a single root element, which is returned by calling getDocumentElement(): Element rootElement = document.getDocumentElement();

DOM Elements, Child Elements, and the Node Interface The root element has children. You get the children of an element like this: NodeList nodes = element.getChildNodes(); for(int i=0; i<nodes.getLength(); i++){ Node node = nodes.item(i); if(node instanceof Element){ //a child element to process Element child = (Element) node; String attribute = child.getAttribute("width"); } http://www3.ntu.edu.sg/home/ehchua/programming/sql/relational_database_design.html

DOM Element Attributes The getChildNodes() method returns a NodeList object, which is a list of Node elements. The Node interface is a superinterface for all of the different node types in DOM The Element interface extends Node and you can access the attributes of an element via the Element interface: String attrValue = element.getAttribute("attrName"); http://www3.ntu.edu.sg/home/ehchua/programming/sql/relational_database_design.html

Examine sub-elements //returns a list of subelements of specified name getElementsByTagName("subelementName"); //returns a list of all child nodes getChildNodes(); A whole complete example is in the below link: https://www.tutorialspoint.com/java_xml/java_dom_ parse_document.htm http://www3.ntu.edu.sg/home/ehchua/programming/sql/relational_database_design.html

Reference https://sanaulla.info/2013/05/23/parsing-xml- using-dom-sax-and-stax-parser-in-java/ https://docs.oracle.com/cd/B28359_01/appdev.1 11/b28394/adx_j_parser.html http://tutorials.jenkov.com/java-xml/dom.html https://www.tutorialspoint.com/java_xml/java_dom _parse_document.htm Drafting out the sample input forms, queries and reports, often helps.