Read XML in Java

First follow this post http://malalanayake.wordpress.com/2012/09/07/write-xml-in-java/

XmlReader.java

[sourcecode language="java"]
package mysamples;

import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Map;
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.NamedNodeMap;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.xml.sax.SAXException;

public class XmlReader {

private String name;
private String content;
private Map<String, String> nameAttributes = new HashMap<String, String>();
private Map<String, ArrayList<XmlReader>> nameChildren = new HashMap<String, ArrayList<XmlReader>>();

public XmlReader(InputStream inputStream, String rootName) {
this(rootElement(inputStream, rootName));
}

public XmlReader(String filename, String rootName) {
this(fileInputStream(filename), rootName);
}

public XmlReader(String rootName) {
this.name = rootName;
}

private XmlReader(Element element) {
this.name = element.getNodeName();
this.content = element.getTextContent();
NamedNodeMap namedNodeMap = element.getAttributes();
int n = namedNodeMap.getLength();
for (int i = 0; i < n; i++) {
Node node = namedNodeMap.item(i);
String name = node.getNodeName();
addAttribute(name, node.getNodeValue());
}
NodeList nodes = element.getChildNodes();
n = nodes.getLength();
for (int i = 0; i < n; i++) {
Node node = nodes.item(i);
int type = node.getNodeType();
if (type == Node.ELEMENT_NODE) {
XmlReader child = new XmlReader((Element) node);
addChild(node.getNodeName(), child);
}

}
}

public void addAttribute(String name, String value) {
nameAttributes.put(name, value);
}

private void addChild(String name, XmlReader child) {
ArrayList<XmlReader> children = nameChildren.get(name);
if (children == null) {
children = new ArrayList<XmlReader>();
nameChildren.put(name, children);
}
children.add(child);
}

public String name() {
return name;
}

public void setContent(String content) {
this.content = content;
}

public String content() {
return content;
}

public void addChild(XmlReader xml) {
addChild(xml.name(), xml);
}

public void addChildren(XmlReader... xmls) {
for (XmlReader xml : xmls) {
addChild(xml.name(), xml);
}
}

public XmlReader child(String name) {
XmlReader child = optChild(name);
if (child == null) {
throw new RuntimeException("Could not find child node: " + name);
}
return child;
}

public XmlReader optChild(String name) {
ArrayList<XmlReader> children = children(name);
int n = children.size();
if (n > 1) {
throw new RuntimeException("Could not find individual child node: " + name);
}
return n == 0 ? null : children.get(0);
}

public boolean option(String name) {
return optChild(name) != null;
}

public ArrayList<XmlReader> children(String name) {
ArrayList<XmlReader> children = nameChildren.get(name);
return children == null ? new ArrayList<XmlReader>() : children;
}

public String string(String name) {
String value = optString(name);
if (value == null) {
throw new RuntimeException(
"Could not find attribute: " + name + ", in node: " + this.name);
}
return value;
}

public String optString(String name) {
return nameAttributes.get(name);
}

public int integer(String name) {
return Integer.parseInt(string(name));
}

public Integer optInteger(String name) {
String string = optString(name);
return string == null ? null : integer(name);
}

public double doubleValue(String name) {
return Double.parseDouble(optString(name));
}

public Double optDouble(String name) {
String string = optString(name);
return string == null ? null : doubleValue(name);
}

private static Element rootElement(InputStream inputStream, String rootName) {
try {
DocumentBuilderFactory builderFactory = DocumentBuilderFactory.newInstance();
DocumentBuilder builder = builderFactory.newDocumentBuilder();
Document document = builder.parse(inputStream);

Element rootElement = document.getDocumentElement();
if (!rootElement.getNodeName().equals(rootName)) {
throw new RuntimeException("Could not find root node: " + rootName);
}
return rootElement;
} catch (IOException exception) {
throw new RuntimeException(exception);
} catch (ParserConfigurationException exception) {
throw new RuntimeException(exception);
} catch (SAXException exception) {
throw new RuntimeException(exception);
} finally {
if (inputStream != null) {
try {
inputStream.close();
} catch (Exception exception) {
throw new RuntimeException(exception);
}
}
}
}

private static FileInputStream fileInputStream(String filename) {
try {
return new FileInputStream(filename);
} catch (IOException exception) {
throw new RuntimeException(exception);
}
}

}
[/sourcecode]


Here I'm Reading the Employee.xml

[sourcecode language="java"]
public static void main(String[] args) {
XmlReader config = new XmlReader("Employee.xml", "employees");

System.out.println("title: " + config.child("employee").content());

for(XmlReader firstname : config.child("employee").children("firstname")){
System.out.println("First Name :" + firstname.content());
}

for(XmlReader firstname : config.child("employee").children("lastname")){
System.out.println("Last Name :" + firstname.content());
}

for(XmlReader firstname : config.child("employee").children("age")){
System.out.println("Age :" + firstname.content());
}

for(XmlReader firstname : config.child("employee").children("email")){
System.out.println("Email :" + firstname.content());
}

}
[/sourcecode]

If You need to read something like this kind of xml you can do it in this way

[sourcecode language="java"]
<config>
<title>test</title>
<version
major="1"
minor="2"/>
<roles>
<role name="admin"/>
<role name="user"/>
</roles>
<users>
<user name="joe" password="pass" role="admin"/>
<user name="harry" password="secret" role="user" email="harry@me.com"/>
</users>
<test/>
</config>
[/sourcecode]


[sourcecode language="java"]
public static void main(String[] args) {
Xml config = new Xml("config.xml","config");

System.out.println("title: "+config.child("title").content());

Xml version = config.child("version");
System.out.println("version: "+version.integer("major")+"."+version.integer("minor"));

for(Xml role:config.child("roles").children("role"))
System.out.println("role: name: "+role.string("name"));

for(Xml user:config.child("users").children("user")) {
String email = user.optString("email");
System.out.println(
"user: name: "+user.string("name")+
", password: "+user.string("password")+
", role: "+user.string("role")+
", email: "+(email==null ? "-" : email));
}

System.out.println("test: "+config.option("test"));
}
[/sourcecode]