Validating XML Documents with Schema Locations

This section describes a tutorial example on how to validate an XML document with schema location assigned inside the XML document using Xerces API.

Providing the schema location directly to the XML Schema processor to validate XML documents in Java is easy with the latest JDK package. Here is a sample program, XsdSchemaValidator.java, used in previous tutorials that loads an XML Schema document to validate any a given XML document:

/* XsdSchemaValidator.java
 - Copyright (c) 2002-2013 HerongYang.com. All Rights Reserved.
 */
import javax.xml.validation.SchemaFactory;
import javax.xml.validation.Schema;
import javax.xml.XMLConstants;
import javax.xml.transform.sax.SAXSource;
import org.xml.sax.InputSource;
import javax.xml.validation.Validator;
import java.io.*;
import org.xml.sax.SAXException;
import org.xml.sax.SAXParseException;
import org.xml.sax.ErrorHandler;
class XsdSchemaValidator {
  private static int errorCount = 0;
  public static void main(String[] a) {
    if (a.length<2) {
      System.out.println("Usage:");
      System.out.println("java XsdSchemaValidator schema_file_name "
        + "xml_file_name");
    } else {
      String schemaName = a[0];
      String xmlName = a[1];
      Schema schema = loadSchema(schemaName);
      validateXml(schema, xmlName);
    }
  }
  public static void validateXml(Schema schema, String xmlName) {
    try {
      // creating a Validator instance
      Validator validator = schema.newValidator();

      // setting my own error handler
      validator.setErrorHandler(new MyErrorHandler());

      // preparing the XML file as a SAX source
      SAXSource source = new SAXSource(
        new InputSource(new java.io.FileInputStream(xmlName)));

      // validating the SAX source against the schema
      validator.validate(source);
      System.out.println();
      if (errorCount>0) {
        System.out.println("Failed with errors: "+errorCount);
      } else {
        System.out.println("Passed.");
      }

    } catch (Exception e) {
      // catching all validation exceptions
      System.out.println();
      System.out.println(e.toString());
    }
  }
  public static Schema loadSchema(String name) {
    Schema schema = null;
    try {
      String language = XMLConstants.W3C_XML_SCHEMA_NS_URI;
      SchemaFactory factory = SchemaFactory.newInstance(language);
      schema = factory.newSchema(new File(name));
    } catch (Exception e) {
      System.out.println(e.toString());
    }
    return schema;
  }
  private static class MyErrorHandler implements ErrorHandler {
    public void warning(SAXParseException e) throws SAXException {
       System.out.println("Warning: ");
       printException(e);
    }
    public void error(SAXParseException e) throws SAXException {
       System.out.println("Error: ");
       printException(e);
    }
    public void fatalError(SAXParseException e) throws SAXException {
       System.out.println("Fattal error: ");
       printException(e);
    }
    private void printException(SAXParseException e) {
      errorCount++;
      System.out.println("   Line number: "+e.getLineNumber());
      System.out.println("   Column number: "+e.getColumnNumber());
      System.out.println("   Message: "+e.getMessage());
      System.out.println();
    }
  }
}

If you run it with in JDK environment to load hello.xsd, and validate hello.xml, you should see no validation errors.

herong> java XsdSchemaValidator hello.xsd hello.xml

Passed.

Obviously, the above program will not work, if the XML Schema document is specified insided the XML document.

One way to perform the schema validation on an XML document with schema location assigned inside the XML document, is to use the Xerces2 API: XMLReader, SAXParser, and other interfaces and classes. Here is a tutorial example of how to use Xerces XMLReader and SAXParser directly:

/* XercesSchemaValidator.java
 - Copyright (c) 2002-2013 HerongYang.com. All Rights Reserved.
 */
import java.io.IOException;
import org.xml.sax.XMLReader;
import org.xml.sax.helpers.DefaultHandler;
import org.xml.sax.helpers.XMLReaderFactory;
import org.xml.sax.SAXException;
import org.xml.sax.SAXParseException;
import org.apache.xerces.parsers.SAXParser;
class XercesSchemaValidator {
  private static int errorCount = 0;
  public static void main(String[] a) {
    if (a.length<1) {
      System.out.println("Usage:");
      System.out.println("java XercesSchemaValidator xml_file");
    } else {
      String name = a[0];
      validateXml(name);
    }
  }
  public static void validateXml(String name) {
    try {
      String parserClass = "org.apache.xerces.parsers.SAXParser";
      String schemaFeature
         = "http://apache.org/xml/features/validation/schema";

      // getting Xerces SAX parser as an XMLReader
      XMLReader parser
         = XMLReaderFactory.createXMLReader(parserClass);

      // setting the parser for XML schema validation
      parser.setFeature(schemaFeature,true);
      parser.setErrorHandler(new MyErrorHandler());

      System.out.println();
      System.out.println("Parsing and validating: "+name);
      parser.parse(name);
      System.out.println();
      if (errorCount>0) {
        System.out.println("Failed with errors: "+errorCount);
      } else {
        System.out.println("Passed.");
      }
    } catch (Exception e) {
      // catching all exceptions
      System.out.println();
      System.out.println(e.toString());
    }
  }
   private static class MyErrorHandler extends DefaultHandler {
    public void warning(SAXParseException e) throws SAXException {
       System.out.println("Warning: ");
       printException(e);
    }
    public void error(SAXParseException e) throws SAXException {
       System.out.println("Error: ");
       printException(e);
    }
    public void fatalError(SAXParseException e) throws SAXException {
       System.out.println("Fattal error: ");
       printException(e);
    }
    private void printException(SAXParseException e) {
      errorCount++;
      System.out.println("   Line number: "+e.getLineNumber());
      System.out.println("   Column number: "+e.getColumnNumber());
      System.out.println("   Message: "+e.getMessage());
      System.out.println();
    }
  }
}

To run the above program, you need to download Xerces2 package and prepare a batch script to include Xerces2 JAR files in the classpath.

herong> type  java_xerces.bat
java -cp .;.\xerces-2_12_1-xml-schema-1.1\xml-apis.jar;
^^^.\xerces-2_12_1-xml-schema-1.1\xercesImpl.jar;
^^^.\xerces-2_12_1-xml-schema-1.1\serializer.jar;
^^^.\xerces-2_12_1-xml-schema-1.1\resolver.jar.jar;
^^^.\xerces-2_12_1-xml-schema-1.1\org.eclipse.wst.xml.xpath2.processor_1.2.0.jar;
^^^.\xerces-2_12_1-xml-schema-1.1\cupv10k-runtime.jar;
^^^.\xerces-2_12_1-xml-schema-1.1\xercesSamples.jar; %1 %2 %3 %4 %5 %6

If you try this on hello.xml that has no schema location assigned, you will get an error:

herong> java_xerces XercesSchemaValidator.java hello.xml

Parsing and validating: hello.xml
Error:
   Line number: 2
   Column number: 4
   Message: cvc-elt.1: Cannot find the declaration of element 'p'.

Failed with errors: 1

If you try this on hello_xsd_no_namespace.xml that has schema location assigned, you will get no errors:

herong> java_xerces XercesSchemaValidator.java hello_xsd_no_namespace.xml

Parsing and validating: hello_xsd_no_namespace.xml

Passed.

If you try this on hello_xsd_no_namespace.xml that has schema location assigned, you will get no errors:

herong> java_xerces XercesSchemaValidator.java hello_xsd_default_namespace.xml

Parsing and validating: hello_xsd_default_namespace.xml

Passed.

Table of Contents

 About This Book

 Introduction to XML Schema

 XML Editor and Schema Processor - XMLPad

 Java API for XML Processing - JAXP

 JAXP - XML Schema (XSD) Validation

 Xerces2 Java Parser - Java API of XML Parsers

 Using Xerces2 Java APIs

 XML Schema Language - Basics

 Introduction of XSD Built-in Datatypes

 "string" and Its Derived Datatypes

 "decimal" and Its Derived Datatypes

 "dateTime" and Its Related Datatypes

 Miscellaneous Built-in Datatypes

 Facets, Constraining Facets and Restriction Datatypes

 "simpleType" - Defining Your Own Simple Datatypes

 Complex Element Declaration

 Identity-Constraints: unique, key and keyref

 Assertion as Custom Validation Rules

XML Schema Location and Namespace in XML Documents

 Assigning XML Schema Location in XML Documents

Validating XML Documents with Schema Locations

 Validating XML Documents with Schema Locations - JAXP

 Assigning XML Schema Location with Namespaces

 Testing XML Schema Location with Namespaces

 Testing XML Schema Location with Namespaces - JAXP

 Overriding Element Types in XML Documents

 Linking Multiple Schema Documents Together

 Glossary

 Archived Tutorials

 References

 Full Version in PDF/EPUB