Como validar XML contra XSD em Java

A API de Validação XML do Java pode ser usada para validar XML contra XSD em um programa Java. A classe javax.xml.validation.Validator é usada neste programa para validar XML contra XSD em Java.

Validar XML contra XSD

Aqui estão os arquivos XSD e XML de exemplo usados. Employee.xsd

<?xml version="1.0" encoding="UTF-8"?>
<schema xmlns="https://www.w3.org/2001/XMLSchema" 
targetNamespace="https://www.journaldev.com/Employee" 
xmlns:empns="https://www.journaldev.com/Employee" elementFormDefault="qualified">

	<element name="empRequest" type="empns:empRequest"></element>
	
	<element name="empResponse" type="empns:empResponse"></element>

	<complexType name="empRequest">
		<sequence>
			<element name="id" type="int"></element>
		</sequence>
	</complexType>
	
	<complexType name="empResponse">
		<sequence>
			<element name="id" type="int"></element>
			<element name="role" type="string"></element>
			<element name="fullName" type="string"></element>
		</sequence>
	</complexType>
</schema>

Observe que o XSD acima contém dois elementos raiz e também um namespace, eu criei dois arquivos XML de exemplo a partir do XSD usando o Eclipse. EmployeeRequest.xml

<?xml version="1.0" encoding="UTF-8"?>
<empns:empRequest xmlns:empns="https://www.journaldev.com/Employee" xmlns:xsi="https://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="https://www.journaldev.com/Employee Employee.xsd ">
  <empns:id>5</empns:id>
</empns:empRequest>

EmployeeResponse.xml

<?xml version="1.0" encoding="UTF-8"?>
<empns:empResponse xmlns:empns="https://www.journaldev.com/Employee" xmlns:xsi="https://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="https://www.journaldev.com/Employee Employee.xsd ">
  <empns:id>1</empns:id>
  <empns:role>Developer</empns:role>
  <empns:fullName>Pankaj Kumar</empns:fullName>
</empns:empResponse>

Aqui está outro arquivo XML que não está em conformidade com o Employee.xsd. employee.xml

<?xml version="1.0"?>
<Employee>
	<name>Pankaj</name>
	<age>29</age>
	<role>Java Developer</role>
	<gender>Male</gender>
</Employee>

Aqui está o programa usado para validar os três arquivos XML contra o XSD. O método validateXMLSchema recebe o XSD e o arquivo XML como argumento e retorna true se a validação for bem-sucedida ou retorna false. XMLValidation.java

package com.journaldev.xml;

import java.io.File;
import java.io.IOException;

import javax.xml.XMLConstants;
import javax.xml.transform.stream.StreamSource;
import javax.xml.validation.Schema;
import javax.xml.validation.SchemaFactory;
import javax.xml.validation.Validator;

import org.xml.sax.SAXException;

public class XMLValidation {

    public static void main(String[] args) {
        
      System.out.println("EmployeeRequest.xml validates against Employee.xsd? "+validateXMLSchema("Employee.xsd", "EmployeeRequest.xml"));
      System.out.println("EmployeeResponse.xml validates against Employee.xsd? "+validateXMLSchema("Employee.xsd", "EmployeeResponse.xml"));
      System.out.println("employee.xml validates against Employee.xsd? "+validateXMLSchema("Employee.xsd", "employee.xml"));
      
      }
    
    public static boolean validateXMLSchema(String xsdPath, String xmlPath){
        
        try {
            SchemaFactory factory = 
                    SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);
            Schema schema = factory.newSchema(new File(xsdPath));
            Validator validator = schema.newValidator();
            validator.validate(new StreamSource(new File(xmlPath)));
        } catch (IOException | SAXException e) {
            System.out.println("Exception: "+e.getMessage());
            return false;
        }
        return true;
    }
}

A saída do programa acima é:

EmployeeRequest.xml validates against Employee.xsd? true
EmployeeResponse.xml validates against Employee.xsd? true
Exception: cvc-elt.1: Cannot find the declaration of element 'Employee'.
employee.xml validates against Employee.xsd? false

A vantagem de usar a API de validação XML do Java é que não precisamos analisar o arquivo e não há uso de APIs de terceiros.