How to Validate XML Against an XSD in Java?

Validating XML against XSD: A Complete Guide

Validating XML documents against an XSD (XML Schema Definition) file is crucial to ensure data integrity and conformance to specified standards. This tutorial will delve into the Java runtime library's capabilities for XML validation and provide a concrete example using the javax.xml.validation.Validator class.

Using the javax.xml.validation API

The Java runtime library offers robust XML validation capabilities through the javax.xml.validation API. The javax.xml.validation.Validator class forms the cornerstone of this API, enabling developers to validate XML documents against a given schema.

Example Code for Validation

The following code snippet demonstrates how to validate an XML file against an XSD schema:

import javax.xml.XMLConstants;
import javax.xml.transform.Source;
import javax.xml.transform.stream.StreamSource;
import javax.xml.validation.*;
import java.net.URL;
import org.xml.sax.SAXException;
//import java.io.File; // if you use File
import java.io.IOException;

...

// Define the XSD schema URL
URL schemaFile = new URL("http://host:port/filename.xsd");

// Create a Source object for the XML file to be validated
Source xmlFile = new StreamSource(new File("web.xml"));

// Create a SchemaFactory instance
SchemaFactory schemaFactory = SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);

try {
  // Create a Schema object from the XSD schema
  Schema schema = schemaFactory.newSchema(schemaFile);

  // Create a Validator object from the Schema object
  Validator validator = schema.newValidator();

  // Validate the XML file against the schema
  validator.validate(xmlFile);

  // Print a success message if validation is successful
  System.out.println(xmlFile.getSystemId() + " is valid");
} catch (SAXException e) {
  // Print an error message if validation fails due to an error
  System.out.println(xmlFile.getSystemId() + " is NOT valid reason:" + e);
} catch (IOException e) {
  // Handle IOException if file is not found or cannot be read
}

Considerations

It's worth noting that using the DOMParser for validation is not recommended if the goal is not to create a DOM object model. This approach can lead to unnecessary resource consumption and is not an efficient method for validation.

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