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.

It will make some XML schema validation tool happier, if the schema location is assigned inside an XML document. However, if you are writing a Java program with JAXP 1.4 to perform the validation, it becomes harder. This is because JAXP 1.4 standard recommends you to provide the schema separately from the XML document dynamically at the time of validation, instead of statically assigned inside the XML document.

In order to perform the schema validation on an XML document with schema location assigned inside the XML document, we need to use the original 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) 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();
    }
  }
}

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

>javac -classpath .;\local\xerces-2_9_1\xercesImpl.jar
   XercesSchemaValidator.java

>java -classpath .;\local\xerces-2_9_1\xercesImpl.jar
   XercesSchemaValidator 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:

>java -classpath .;\local\xerces-2_9_1\xercesImpl.jar
    XercesSchemaValidator hello_xsd_no_namespace.xml

Parsing and validating: hello_xsd_no_namespace.xml

Passed.

Conclusion:

Last update: 2013.

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 API

 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

 References

 PDF Printing Version