XSD Schema XML DOM Validator - XsdSchemaDomValidator.java

XML Schema Tutorials - Herong's Tutorial Examples

Dr. Herong Yang, Version 4.00

<< XML Schema Tutorials - Herong's Tutorial Examples

This section describes a tutorial example on how to create a Validator instance from an XSD Schema instance to validate an XML file using the JAXP DOM interface.

After creating an XSD Schema instance from the XSD schema file, we are ready to create a Validator instance from the schema instance. This Validator instance can then be used to validate an XML file represented with the DOM interface or the SAX interface.

Let's try the DOM interface first. If you need to learn DOM interface, you can read the XML file DOM parser tutorial example described in another chapter of this book.

Here is a tutorial example program called XsdSchemaDomValidator.java that validates an XML file against an XSD file using the DOM interface:

/*
 * XsdSchemaDomValidator.java
 * Copyright (c) 2007 by Dr. Herong Yang. All rights reserved.
 */
import javax.xml.validation.SchemaFactory;
import javax.xml.validation.Schema;
import javax.xml.XMLConstants;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.DocumentBuilder;
import org.w3c.dom.Document;
import javax.xml.validation.Validator;
import javax.xml.transform.dom.DOMSource;
import java.io.File;
class XsdSchemaDomValidator {
  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);
      Document document = parseXmlDom(xmlName);
      validateXml(schema, document);
    }
  }
  public static void validateXml(Schema schema, Document document) {
    try {
      // creating a Validator instance
      Validator validator = schema.newValidator();
      System.out.println();
      System.out.println("Validator Class: "
        + validator.getClass().getName());

      // validating the document against the schema
      validator.validate(new DOMSource(document));
      System.out.println();
      System.out.println("Validation 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;
  }
  public static Document parseXmlDom(String name) {
    Document document = null;
    try {
      DocumentBuilderFactory factory 
         = DocumentBuilderFactory.newInstance();
      DocumentBuilder builder = factory.newDocumentBuilder();
      document = builder.parse(new File(name));
    } catch (Exception e) {
      System.out.println(e.toString());
    }
    return document;
  }
}

As the first test, let's try to validate the following simple XML file, first_html.xml, against the simple XSD schema file, first_html.xsd:

>type first_html.xsd
<?xml version = "1.0" encoding = "utf-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
  elementFormDefault="qualified" attributeFormDefault="unqualified">
 <xs:element name="html" type="htmlType"/>
 <xs:complexType name="htmlType">
  <xs:sequence>
   <xs:element name="body" type="xs:string"/>
  </xs:sequence>
 </xs:complexType>
</xs:schema>

>type first_html.xml
<?xml version = "1.0" encoding = "utf-8"?>
<html>
<body>My first HTML document in XML format.</body>
</html>

>javac XsdSchemaDomValidator.java

>java XsdSchemaDomValidator first_html.xsd first_html.xml

Validator Class: com.sun.org.apache.xerces.internal.jaxp
   .validation.ValidatorImpl

Validation passed.

The output shows that:

The default implemenation class of the Validator class is also from the Apache Xerces project.
The validation passed successfully. No exceptions raised.

Sections in This Chapter

Standard Steps to Validate XML Docuements Against a Schema

XSD Schema File Loader - XsdSchemaLoader.java

XSD Schema File Loading Errors

XSD Schema XML DOM Validator - XsdSchemaDomValidator.java

XSD Schema XML DOM Validation Errors

XSD Schema XML DOM Validator with Error Handler

XSD Schema XML SAX Validator - XsdSchemaSaxValidator.java

XSD Schema XML SAX Validation Errors

XSD Schema XML SAX Validator with Error Handler

XSD Schema XML Validator - Final Version

Dr. Herong Yang, updated in 2007

XSD Schema XML DOM Validator - XsdSchemaDomValidator.java