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Java - parsing xml using DOM

I am trying to parse the following xml. I can easily access WeekNumber, but cannot access children for EmployeeRatesLevelA and EmployeeRatesLevelB. The goal is to store them in the DataSet class with the fields WeekNumber and ArrayLists, EmployeeRatesLevelA and EmployeeRatesLevelB. Thanks.

<DataSet ActiveFrom="2011/04/06"> <WeekNumber>8</WeekNumber> <EmployeeRatesLevelA> <Rate>0</Rate> <Rate>0.12</Rate> </EmployeeRatesLevelA> <EmployeeRatesLevelB> <Rate>0.15</Rate> <Rate>0.20</Rate> </EmployeeRatesLevelB> </DataSet> Document doc = loadXml("data.xml"); NodeList nodeList = doc.getElementsByTagName("DataSet"); for (int i = 0; i < nodeList.getLength(); i++) { Node node = nodeList.item(i); if (node.getNodeType() == Node.ELEMENT_NODE) { Element element = (Element) node; NodeList weekNumberList = element.getElementsByTagName("WeekNumber"); Element weekElement = (Element) weekNumberList.item(0); NodeList textElementList = weekElement.getChildNodes(); System.out.println("Weeknumber:"+ ((Node)textElementList.item(0)).getNodeValue().trim()); } public static Document loadXml(String file) { try { return (DocumentBuilderFactory.newInstance().newDocumentBuilder().parse(new File(file))); } catch (SAXException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } catch (ParserConfigurationException e) { e.printStackTrace(); } return null; }

This gives me the week number, but I cannot access EmployeeRatesLevelA and EmployeeRatesLevelB.

I would like to learn other interesting things, but since I'm new to Java and the XML document is really small, the DOM should be sufficient.

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4 answers

If you want to use the DOM, I suggest you start by writing some helper classes to make your work easier. Here is one that I wrote recently for personal use.

Let's start with the helper classes in the xml.utils package

XmlException.java

 package xml.utils; public class XmlException extends Exception { private static final long serialVersionUID = 1L; public XmlException(String message, Throwable cause) { super(message, cause); } public XmlException(String message) { super(message); } public XmlException(Throwable cause) { super(cause); } }

XmlDocument.java

 package xml.utils; import java.io.File; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import java.io.Writer; import javax.xml.parsers.DocumentBuilder; import javax.xml.parsers.DocumentBuilderFactory; import javax.xml.parsers.ParserConfigurationException; import javax.xml.transform.Transformer; import javax.xml.transform.TransformerConfigurationException; import javax.xml.transform.TransformerException; import javax.xml.transform.TransformerFactory; import javax.xml.transform.dom.DOMSource; import javax.xml.transform.stream.StreamResult; import org.w3c.dom.Document; import org.w3c.dom.Element; import org.xml.sax.SAXException; public class XmlDocument { private Document document; public XmlNode parse(InputStream is) throws XmlException { try { DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance(); DocumentBuilder dBuilder = dbFactory.newDocumentBuilder(); document = dBuilder.parse(is); document.getDocumentElement().normalize(); XmlNode node = new XmlNode(document.getDocumentElement()); return node; } catch (ParserConfigurationException e) { throw new XmlException("Error in configuration of XML parser", e); } catch (SAXException e) { throw new XmlException("Error in parsing XML document", e); } catch (IOException e) { throw new XmlException("Error in reading InputStream", e); } } public XmlNode parse(String uri) throws XmlException { try { DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance(); DocumentBuilder dBuilder = dbFactory.newDocumentBuilder(); document = dBuilder.parse(uri); document.getDocumentElement().normalize(); XmlNode node = new XmlNode(document.getDocumentElement()); return node; } catch (ParserConfigurationException e) { throw new XmlException("Error in configuration of XML parser", e); } catch (SAXException e) { throw new XmlException("Error in parsing XML document", e); } catch (IOException e) { throw new XmlException("Error in opening URI", e); } } public XmlNode parse(File file) throws XmlException { try { DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance(); DocumentBuilder dBuilder = dbFactory.newDocumentBuilder(); document = dBuilder.parse(file); document.getDocumentElement().normalize(); XmlNode node = new XmlNode(document.getDocumentElement()); return node; } catch (ParserConfigurationException e) { throw new XmlException("Error in configuration of XML parser", e); } catch (SAXException e) { throw new XmlException("Error in parsing XML document", e); } catch (IOException e) { throw new XmlException("Error in opening file", e); } } public void write(OutputStream os, XmlNode node) throws XmlException { try { if (document == null) { document = createNewDocument(); } document.appendChild(node.getNode()); // write the content into xml file TransformerFactory transformerFactory = TransformerFactory.newInstance(); Transformer transformer = transformerFactory.newTransformer(); DOMSource source = new DOMSource(document); StreamResult result = new StreamResult(os); transformer.transform(source, result); } catch (TransformerConfigurationException e) { throw new XmlException("Error in configuration of XML writer", e); } catch (TransformerException e) { throw new XmlException("Error in writing XML", e); } } public void write(File file, XmlNode node) throws XmlException { try { if (document == null) { document = createNewDocument(); } document.appendChild(node.getNode()); // write the content into xml file TransformerFactory transformerFactory = TransformerFactory.newInstance(); Transformer transformer = transformerFactory.newTransformer(); DOMSource source = new DOMSource(document); StreamResult result = new StreamResult(file); transformer.transform(source, result); } catch (TransformerConfigurationException e) { throw new XmlException("Error in configuration of XML writer", e); } catch (TransformerException e) { throw new XmlException("Error in writing XML", e); } } public void write(Writer writer, XmlNode node) throws XmlException { try { if (document == null) { document = createNewDocument(); } document.appendChild(node.getNode()); // write the content into xml file TransformerFactory transformerFactory = TransformerFactory.newInstance(); Transformer transformer = transformerFactory.newTransformer(); DOMSource source = new DOMSource(document); StreamResult result = new StreamResult(writer); transformer.transform(source, result); } catch (TransformerConfigurationException e) { throw new XmlException("Error in configuration of XML writer", e); } catch (TransformerException e) { throw new XmlException("Error in writing XML", e); } } private Document createNewDocument() throws XmlException { try { DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance(); DocumentBuilder dBuilder = dbFactory.newDocumentBuilder(); return dBuilder.newDocument(); } catch (ParserConfigurationException e) { throw new XmlException("Error in configuration of XML parser", e); } } public XmlNode createNode(String nodeName) throws XmlException { if (document == null) { document = createNewDocument(); } XmlNode node = new XmlNode(this, document.createElement(nodeName)); return node; } XmlNode createNode(String nodeName, String nodeValue) throws XmlException { if (document == null) { document = createNewDocument(); } Element node = document.createElement(nodeName); node.appendChild(document.createTextNode(nodeValue)); return new XmlNode(this, node); } }

XmlNode.java

 package xml.utils; import java.util.ArrayList; import java.util.List; import org.w3c.dom.Element; import org.w3c.dom.Node; import org.w3c.dom.NodeList; public class XmlNode { private Element node; private XmlDocument parent; XmlNode(Element node) { this.node = node; this.parent = null; } XmlNode(XmlDocument parent, Element node) { this.node = node; this.parent = parent; } Node getNode() { return node; } public String getNodeValue() { return node.getTextContent(); } public XmlDocument getParent() { return parent; } public void setParent(XmlDocument parent) { this.parent = parent; } public List<XmlNode> getChildNodes() { List<XmlNode> list = new ArrayList<XmlNode>(); NodeList nodeList = node.getChildNodes(); for (int i = 0; i < nodeList.getLength(); i++) { Node n = nodeList.item(i); if (n.getNodeType() == Node.ELEMENT_NODE) { list.add(new XmlNode((Element) n)); } } return list; } public XmlNode getFirstChild() { return getChildNodes().get(0); } public XmlNode getLastChild() { List<XmlNode> childs = getChildNodes(); if (childs.size() == 0) return null; return childs.get(childs.size() - 1); } public List<XmlNode> getNodesByTagName(String tagName) { List<XmlNode> list = new ArrayList<XmlNode>(); NodeList nodeList = node.getElementsByTagName(tagName); for (int i = 0; i < nodeList.getLength(); i++) { Node n = nodeList.item(i); if (n.getNodeType() == Node.ELEMENT_NODE) { list.add(new XmlNode((Element) n)); } } return list; } public XmlNode getFirstNodeByTagName(String tagName) { return getNodesByTagName(tagName).get(0); } public String getTagValue(String tagName) throws XmlException { NodeList tagList = node.getElementsByTagName(tagName); if (tagList.getLength() == 0) throw new XmlException("Tag: '" + tagName + "' not present"); NodeList nlList = tagList.item(0).getChildNodes(); Node nValue = (Node) nlList.item(0); return nValue.getNodeValue(); } public String getAttributeValue(String attributeName) { return node.getAttribute(attributeName); } public String getNodeName() { return node.getTagName(); } public void setAttribute(String name, String value) throws XmlException { if (parent == null) throw new XmlException("Parent node not present."); node.setAttribute(name, value); } public void setTag(String name, String value) throws XmlException { if (parent == null) throw new XmlException("Parent node not present."); XmlNode xmlNode = parent.createNode(name, value); node.appendChild(xmlNode.node); } public void addChildNode(XmlNode xmlNode) throws XmlException { if (parent == null) throw new XmlException("Parent node not present."); node.appendChild(xmlNode.node); } public XmlNode addChildNode(String nodeName) throws XmlException { if (parent == null) throw new XmlException("Parent node not present."); XmlNode child = parent.createNode(nodeName); node.appendChild(child.getNode()); return child; } }

Now DataSet.java and Main.java look like this:

Dataset.java

 package tests; import java.io.File; import java.util.ArrayList; import java.util.List; import xml.utils.XmlDocument; import xml.utils.XmlException; import xml.utils.XmlNode; public class DataSet { private int weekNumber; private List<Float> employeeRatesLevelA; private List<Float> employeeRatesLevelB; public DataSet(File xml) throws XmlException { employeeRatesLevelA = new ArrayList<Float>(); employeeRatesLevelB = new ArrayList<Float>(); loadFromXml(xml); } private void loadFromXml(File xml) throws XmlException { XmlDocument document = new XmlDocument(); XmlNode root = document.parse(xml); weekNumber = Integer.parseInt(root.getTagValue("WeekNumber")); XmlNode ratesLevelNode = root.getNodesByTagName("EmployeeRatesLevelA").get(0); List<XmlNode> rates = ratesLevelNode.getNodesByTagName("Rate"); for (XmlNode xmlNode : rates) { employeeRatesLevelA.add(Float.parseFloat(xmlNode.getNodeValue())); } ratesLevelNode = root.getNodesByTagName("EmployeeRatesLevelB").get(0); rates = ratesLevelNode.getNodesByTagName("Rate"); for (XmlNode xmlNode : rates) { employeeRatesLevelB.add(Float.parseFloat(xmlNode.getNodeValue())); } } public void display() { System.out.println("WeekNumber: " + weekNumber); System.out.println("Level A"); for (Float rate : employeeRatesLevelA) { System.out.println("\tRate: " + rate); } System.out.println("Level B"); for (Float rate : employeeRatesLevelB) { System.out.println("\tRate: " + rate); } } }

Main.java

 package tests; import java.io.File; import java.io.IOException; import org.xml.sax.SAXException; import xml.utils.XmlException; public class Main { public static void main(String[] args) throws SAXException, IOException, XmlException { File dataFile = new File("/home/jomit/data.xml"); DataSet dataSet = new DataSet(dataFile); dataSet.display(); } }
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As mentioned in the comments, please show us your Java code. You might also consider looking at JAXB, the Java architecture for XML binding. It is specifically designed to represent XML as Java objects. This may not be practical for your solution for any reason, but definitely look:

http://jaxb.java.net/tutorial/

Dataset

The following is the domain object described below:

The goal is to store them in the DataSet class with the fields WeekNumber and ArrayLists, EmployeeRatesLevelA and EmployeeRatesLevelB.

 package forum8345529; import java.util.List; import javax.xml.bind.annotation.*; @XmlRootElement(name="DataSet") @XmlAccessorType(XmlAccessType.FIELD) public class DataSet { @XmlElement(name="WeekNumber") private int weekNumber; @XmlElementWrapper(name="EmployeeRatesLevelA") @XmlElement(name="Rate") private List<Float> employeeRatesLevelA; @XmlElementWrapper(name="EmployeeRatesLevelB") @XmlElement(name="Rate") private List<Float> employeeRatesLevelB; }

Demo

The following code demonstrates how to use the JAXB runtime to convert your XML to / from your domain objects:

 package forum8345529; import java.io.File; import javax.xml.bind.*; public class Demo { public static void main(String[] args) throws Exception{ JAXBContext jc = JAXBContext.newInstance(DataSet.class); Unmarshaller unmarshaller = jc.createUnmarshaller(); File xml = new File("src/forum8345529/input.xml"); DataSet dataSet = (DataSet) unmarshaller.unmarshal(xml); Marshaller marshaller = jc.createMarshaller(); marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true); marshaller.marshal(dataSet, System.out); } }
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Element.getElementsByTagName ("EmployeeRatesLevelA"), where Element should be a DataSet. Or you can use http://java.sun.com/javase/6/docs/api/org/w3c/dom/Node.html#getChildNodes ()

then filter out all the children until you find the ones you want.

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I really like groovy for these things, especially if this is the one for loading material into the database:

http://groovy.codehaus.org/Reading+XML+using+Groovy%27s+XmlSlurper

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Source: https://habr.com/ru/post/1345820/

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