XML Coding Notes

Learn XML Coding

1. Introduction to XML

XML (eXtensible Markup Language) is a markup language used to store and transport data in a structured format. It is both human-readable and machine-readable.

2. XML Syntax

<?xml version="1.0" encoding="UTF-8"?>
<note>
    <to>John</to>
    <from>Alice</from>
    <message>Hello, how are you?</message>
</note>

3. XML Elements & Tags

Elements are the building blocks of XML, enclosed in start and end tags.

<book>
    <title>XML Guide</title>
    <author>John Doe</author>
    <year>2025</year>
</book>

4. XML Attributes

Attributes provide additional information about an element.

<book title="XML Guide" author="John Doe" year="2025"></book>

5. XML Namespaces

Namespaces prevent element name conflicts.

<root xmlns:lib="http://www.library.com">
    <lib:book>
        <lib:title>XML Guide</lib:title>
    </lib:book>
</root>

6. XML Schemas (XSD)

XML Schema (XSD) defines the structure and rules for an XML document.

<xs:element name="book">
    <xs:complexType>
        <xs:sequence>
            <xs:element name="title" type="xs:string"/>
            <xs:element name="author" type="xs:string"/>
        </xs:sequence>
    </xs:complexType>
</xs:element>

7. XML Parsing

Parsing converts XML into readable or usable formats for applications.

Java Example:

import javax.xml.parsers.*;
import org.w3c.dom.*;

public class XMLParser {
    public static void main(String[] args) throws Exception {
        DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
        DocumentBuilder builder = factory.newDocumentBuilder();
        Document doc = builder.parse("file.xml");

        NodeList list = doc.getElementsByTagName("title");
        System.out.println(list.item(0).getTextContent());
    }
}

8. XSLT (Extensible Stylesheet Language Transformations)

XSLT is used to transform XML data into other formats (like HTML).

<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
    <xsl:template match="/">
        <html>
            <body>
                <h2>Book List</h2>
                <xsl:for-each select="library/book">
                    <p><xsl:value-of select="title"/> by <xsl:value-of select="author"/></p>
                </xsl:for-each>
            </body>
        </html>
    </xsl:template>
</xsl:stylesheet>

9. Applications of XML

Configuration files (e.g., AndroidManifest.xml in Android)
Data storage and exchange (e.g., RSS feeds, Web Services)
APIs (e.g., SOAP APIs)
UI Layouts (e.g., Android UI)

10. Conclusion

XML is a powerful language for data storage and transmission. It plays a key role in APIs, configurations, and structured document formatting.