As the whole document is stored in memory at once, it is preferred for only small documents.
- It is a tree model parser (Object-based).
- First, it loads the file into the memory and then parses the file.
- It has memory constraints since it loads the whole XML file before parsing.
- It supports both read and write operations.
- Backward and forward searches are possible for searching the tags and evaluating the information inside the tags.
- It is slower at run time.
Content of Employee.java
package com.t4b.parser.dom.test;
public class Employee {
private String name;
private int age;
private int id;
private String type;
public Employee(String name, int id, int age, String type) {
this.name = name;
this.age = age;
this.id = id;
this.type = type;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getType() {
return type;
}
public void setType(String type) {
this.type = type;
}
public String toString() {
StringBuffer sb = new StringBuffer();
sb.append("Employee Details - ");
sb.append("Name:" + getName());
sb.append(", ");
sb.append("Type:" + getType());
sb.append(", ");
sb.append("Id:" + getId());
sb.append(", ");
sb.append("Age:" + getAge());
sb.append(".");
return sb.toString();
}
}
Content of DomParserTest.java
package com.t4b.parser.dom.test;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
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;
import org.w3c.dom.NodeList;
import org.xml.sax.SAXException;
public class DomParserTest {
List<Employee> myEmpls;
Document dom;
public DomParserTest() {
myEmpls = new ArrayList<Employee>();
}
public void runExample(String filename) {
parseXmlFile(filename);
parseDocument();
printData();
}
private void parseXmlFile(String filename) {
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
try {
DocumentBuilder db = dbf.newDocumentBuilder();
dom = db.parse(filename);
} catch (ParserConfigurationException pce) {
pce.printStackTrace();
} catch (SAXException se) {
se.printStackTrace();
} catch (IOException ioe) {
ioe.printStackTrace();
}
}
private void parseDocument() {
Element docEle = dom.getDocumentElement();
NodeList nl = docEle.getElementsByTagName("Employee");
if (nl != null && nl.getLength() > 0) {
for (int i = 0; i < nl.getLength(); i++) {
Element el = (Element) nl.item(i);
Employee e = getEmployee(el);
myEmpls.add(e);
}
}
}
private Employee getEmployee(Element empEl) {
String name = getTextValue(empEl, "Name");
int id = getIntValue(empEl, "Id");
int age = getIntValue(empEl, "Age");
String type = empEl.getAttribute("type");
Employee e = new Employee(name, id, age, type);
return e;
}
private String getTextValue(Element ele, String tagName) {
String textVal = null;
NodeList nl = ele.getElementsByTagName(tagName);
if (nl != null && nl.getLength() > 0) {
Element el = (Element) nl.item(0);
textVal = el.getFirstChild().getNodeValue();
}
return textVal;
}
private int getIntValue(Element ele, String tagName) {
return Integer.parseInt(getTextValue(ele, tagName));
}
private void printData() {
System.out.println("No of Employees '" + myEmpls.size() + "'.");
Iterator<Employee> it = myEmpls.iterator();
while (it.hasNext()) {
System.out.println(it.next().toString());
}
}
public static void main(String[] args) {
DomParserTest dpt = new DomParserTest();
dpt.runExample("employees.xml");
}
}
Content of employees.xml document for parsing
<?xml version="1.0" encoding="UTF-8"?>
<Personnel>
<Employee type="permanent">
<Name>John</Name>
<Id>1000</Id>
<Age>34</Age>
</Employee>
<Employee type="contract">
<Name>Robin</Name>
<Id>1001</Id>
<Age>25</Age>
</Employee>
<Employee type="permanent">
<Name>Neil</Name>
<Id>1002</Id>
<Age>26</Age>
</Employee>
</Personnel>
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