XML Validation with XSD, Directory Repository, and JAXP DOM for XSLT

Question

Background

Using JDK 6 to load XML files into the DOM . XML files should be validated against XSD. The location of the XSD file differs depending on the environment. Ensuring that XML can be validated using XSD, regardless of directory structure, requires a directory resolver. Once XML is validated, it can be converted.

I understand that DocumentBuilderFactory can be used to set up such a check. This is achieved by using DocumentBuilder with XMLCatalogResolver to find the XSD file (and any included files) associated with the XML file.

Questions about validating XML documents using directory-based XSD include:

• JAXP - debug XSD directory lookup
• Java XML Schema validator with custom resource adapter cannot resolve elements
• Can XMLCatalog be used to import a schema?
• How to download XMLCatalog from class resources (inside the jar), reliably?
• XMLSchema validation with Catalog.xml to solve the problem
• Removing type definitions from an imported schema in XJC fails
• Find elements that can be repeated in xml schema using Java
• Java servlets: xml vs xsd validation

Most of these questions and answers refer to a hard XSD file or use SAX to perform validation or compliance in a DTD or require a JDOM dependency or no conversion .

Problem

There is no canonical solution that describes how to use the XML directory to validate XSD using the JAXP DOM, which is subsequently converted via XSLT. There are number fragments , but not a complete, stand-alone example that compiles and runs (under JDK 6).

I posted an answer that seems to work technically, but too verbose.

Question

What is the canonical way (using the JDK 1.6 libraries) to validate and transform an XML document? Here is one of the possible algorithms:

• Create a directory resolver.
• Create an XML parser.
• Associate the recognizer with the parser.
• Parse the XML document containing the XSD link.
• Complete validation errors.
• Convert validated XML using an XSL template.

Answer 1

Source files

Source files include the catalog manager properties file, Java source code, catalog file, XML data, XSL files, and XSD files. All files are in the current working directory ( ./ ).

Directory Manager Properties File

This property file is read by the CatalogResolver class; save as ./CatalogManager.properties :

 catalogs=catalog.xml relative-catalogs=yes verbosity=99 prefer=system static-catalog=yes allow-oasis-xml-catalog-pi=yes 

TestXSD.java

This is the main application; save it as ./src/TestXSD.java :

 package src; import java.io.*; import java.net.URI; import java.util.*; import java.util.regex.Pattern; import java.util.regex.Matcher; import javax.xml.parsers.*; import javax.xml.xpath.*; import javax.xml.XMLConstants; import org.w3c.dom.*; import org.xml.sax.*; import org.apache.xml.resolver.tools.CatalogResolver; import org.apache.xerces.util.XMLCatalogResolver; import static org.apache.xerces.jaxp.JAXPConstants.JAXP_SCHEMA_LANGUAGE; import static org.apache.xerces.jaxp.JAXPConstants.W3C_XML_SCHEMA; import javax.xml.validation.SchemaFactory; import javax.xml.validation.Schema; import javax.xml.validation.Validator; import javax.xml.transform.Result; import javax.xml.transform.Source; import javax.xml.transform.Transformer; import javax.xml.transform.TransformerFactory; import javax.xml.transform.dom.DOMSource; import javax.xml.transform.sax.SAXSource; import javax.xml.transform.stream.StreamResult; import javax.xml.transform.stream.StreamSource; /** * Download http://xerces.apache.org/xml-commons/components/resolver/CatalogManager.properties */ public class TestXSD { private final static String ENTITY_RESOLVER = "http://apache.org/xml/properties/internal/entity-resolver"; /** * This program reads an XML file, performs validation, reads an XSL * file, transforms the input XML, and then writes the transformed document * to standard output. * * args[0] - The XSL file used to transform the XML file * args[1] - The XML file to transform using the XSL file */ public static void main( String args[] ) throws Exception { // For validation error messages. ErrorHandler errorHandler = new DocumentErrorHandler(); // Read the CatalogManager.properties file. CatalogResolver resolver = new CatalogResolver(); XMLCatalogResolver xmlResolver = createXMLCatalogResolver( resolver ); logDebug( "READ XML INPUT SOURCE" ); // Load an XML document in preparation to transform it. InputSource xmlInput = new InputSource( new InputStreamReader( new FileInputStream( args[1] ) ) ); DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance(); dbFactory.setAttribute( JAXP_SCHEMA_LANGUAGE, W3C_XML_SCHEMA ); dbFactory.setNamespaceAware( true ); DocumentBuilder builder = dbFactory.newDocumentBuilder(); builder.setEntityResolver( xmlResolver ); builder.setErrorHandler( errorHandler ); logDebug( "PARSE XML INTO DOCUMENT MODEL" ); Document xmlDocument = builder.parse( xmlInput ); logDebug( "CONVERT XML DOCUMENT MODEL INTO DOMSOURCE" ); DOMSource xml = new DOMSource( xmlDocument ); logDebug( "GET XML SCHEMA DEFINITION" ); String schemaURI = getSchemaURI( xmlDocument ); logDebug( "SCHEMA URI: " + schemaURI ); if( schemaURI != null ) { logDebug( "CREATE SCHEMA FACTORY" ); // Create a Schema factory to obtain a Schema for XML validation... SchemaFactory sFactory = SchemaFactory.newInstance( W3C_XML_SCHEMA ); sFactory.setResourceResolver( xmlResolver ); logDebug( "CREATE XSD INPUT SOURCE" ); String xsdFileURI = xmlResolver.resolveURI( schemaURI ); logDebug( "CREATE INPUT SOURCE XSD FROM: " + xsdFileURI ); InputSource xsd = new InputSource( new FileInputStream( new File( new URI( xsdFileURI ) ) ) ); logDebug( "CREATE SCHEMA OBJECT FOR XSD" ); Schema schema = sFactory.newSchema( new SAXSource( xsd ) ); logDebug( "CREATE VALIDATOR FOR SCHEMA" ); Validator validator = schema.newValidator(); logDebug( "VALIDATE XML AGAINST XSD" ); validator.validate( xml ); } logDebug( "READ XSL INPUT SOURCE" ); // Load an XSL template for transforming XML documents. InputSource xslInput = new InputSource( new InputStreamReader( new FileInputStream( args[0] ) ) ); logDebug( "PARSE XSL INTO DOCUMENT MODEL" ); Document xslDocument = builder.parse( xslInput ); transform( xmlDocument, xslDocument, resolver ); System.out.println(); } private static void transform( Document xml, Document xsl, CatalogResolver resolver ) throws Exception { if( versionAtLeast( xsl, 2 ) ) { useXSLT2Transformer(); } logDebug( "CREATE TRANSFORMER FACTORY" ); // Create the transformer used for the document. TransformerFactory tFactory = TransformerFactory.newInstance(); tFactory.setURIResolver( resolver ); logDebug( "CREATE TRANSFORMER FROM XSL" ); Transformer transformer = tFactory.newTransformer( new DOMSource( xsl ) ); logDebug( "CREATE RESULT OUTPUT STREAM" ); // This enables writing the results to standard output. Result out = new StreamResult( new OutputStreamWriter( System.out ) ); logDebug( "TRANSFORM THE XML AND WRITE TO STDOUT" ); // Transform the document using a given stylesheet. transformer.transform( new DOMSource( xml ), out ); } /** * Answers whether the given XSL document version is greater than or * equal to the given required version number. * * @param xsl The XSL document to check for version compatibility. * @param version The version number to compare against. * * @return true iff the XSL document version is greater than or equal * to the version parameter. */ private static boolean versionAtLeast( Document xsl, float version ) { Element root = xsl.getDocumentElement(); float docVersion = Float.parseFloat( root.getAttribute( "version" ) ); return docVersion >= version; } /** * Enables Saxon9 XSLT2 transformer for XSLT2 files. */ private static void useXSLT2Transformer() { System.setProperty("javax.xml.transform.TransformerFactory", "net.sf.saxon.TransformerFactoryImpl"); } /** * Creates an XMLCatalogResolver based on the file names found in * the given CatalogResolver. The resulting XMLCatalogResolver will * contain the absolute path to all the files known to the given * CatalogResolver. * * @param resolver The CatalogResolver to examine for catalog file names. * @return An XMLCatalogResolver instance with the same number of catalog * files as found in the given CatalogResolver. */ private static XMLCatalogResolver createXMLCatalogResolver( CatalogResolver resolver ) { int index = 0; List files = resolver.getCatalog().getCatalogManager().getCatalogFiles(); String catalogs[] = new String[ files.size() ]; XMLCatalogResolver xmlResolver = new XMLCatalogResolver(); for( Object file : files ) { catalogs[ index ] = (new File( file.toString() )).getAbsolutePath(); index++; } xmlResolver.setCatalogList( catalogs ); return xmlResolver; } private static String[] parseNameValue( String nv ) { Pattern p = Pattern.compile( "\\s*(\\w+)=\"([^\"]*)\"\\s*" ); Matcher m = p.matcher( nv ); String result[] = new String[2]; if( m.find() ) { result[0] = m.group(1); result[1] = m.group(2); } return result; } /** * Retrieves the XML schema definition using an XSD. * * @param node The document (or child node) to traverse seeking processing * instruction nodes. * @return null if no XSD is present in the XML document. * @throws IOException Never thrown (uses StringReader). */ private static String getSchemaURI( Node node ) throws IOException { String result = null; if( node.getNodeType() == Node.PROCESSING_INSTRUCTION_NODE ) { ProcessingInstruction pi = (ProcessingInstruction)node; logDebug( "NODE IS PROCESSING INSTRUCTION" ); if( "xml-model".equals( pi.getNodeName() ) ) { logDebug( "PI IS XML MODEL" ); // Hack to get the attributes. String data = pi.getData(); if( data != null ) { final String attributes[] = pi.getData().trim().split( "\\s+" ); String type = parseNameValue( attributes[0] )[1]; String href = parseNameValue( attributes[1] )[1]; // TODO: Schema should = http://www.w3.org/2001/XMLSchema //String schema = attributes.getNamedItem( "schematypens" ); if( "application/xml".equalsIgnoreCase( type ) && href != null ) { result = href; } } } } else { // Try to get the schema type information. NamedNodeMap attrs = node.getAttributes(); if( attrs != null ) { // TypeInfo.toString() returns values of the form: // schemaLocation="uri schemaURI" // The following loop extracts the schema URI. for( int i = 0; i < attrs.getLength(); i++ ) { Attr attribute = (Attr)attrs.item( i ); TypeInfo typeInfo = attribute.getSchemaTypeInfo(); String attr[] = parseNameValue( typeInfo.toString() ); if( "schemaLocation".equalsIgnoreCase( attr[0] ) ) { result = attr[1].split( "\\s" )[1]; break; } } } // Look deeper for the schema URI. if( result == null ) { NodeList list = node.getChildNodes(); for( int i = 0; i < list.getLength(); i++ ) { result = getSchemaURI( list.item( i ) ); if( result != null ) { break; } } } } return result; } /** * Writes a message to standard output. */ private static void logDebug( String s ) { System.out.println( s ); } } 

Error handler

This is code for user-friendly error messages; save as ./src/DocumentErrorHandler.java :

 package src; import java.io.PrintStream; import org.xml.sax.ErrorHandler; import org.xml.sax.SAXParseException; import org.xml.sax.SAXException; /** * Handles error messages during parsing and validating XML documents. */ public class DocumentErrorHandler implements ErrorHandler { private final static PrintStream OUTSTREAM = System.err; private void log( String type, SAXParseException e ) { OUTSTREAM.println( "SAX PARSE EXCEPTION " + type ); OUTSTREAM.println( " Public ID: " + e.getPublicId() ); OUTSTREAM.println( " System ID: " + e.getSystemId() ); OUTSTREAM.println( " Line : " + e.getLineNumber() ); OUTSTREAM.println( " Column : " + e.getColumnNumber() ); OUTSTREAM.println( " Message : " + e.getMessage() ); } @Override public void error( SAXParseException e ) throws SAXException { log( "ERROR", e ); } @Override public void fatalError( SAXParseException e ) throws SAXException { log( "FATAL ERROR", e ); } @Override public void warning( SAXParseException e ) throws SAXException { log( "WARNING", e ); } } 

Catalog file

Save as ./catalog.xml :

 <?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE catalog PUBLIC "-//OASIS//DTD XML Catalogs V1.1//EN" "http://www.oasis-open.org/committees/entity/release/1.1/catalog.dtd"> <catalog xmlns="urn:oasis:names:tc:entity:xmlns:xml:catalog"> <!-- XSDs linked through primary catalog --> <!-- catalog entry for good-note1.xml --> <rewriteSystem systemIdStartString="http://stackoverflow.com/schema" rewritePrefix="./ArbitraryFolder/schemas" /> <!-- catalog entry for good-note2.xml, good-note3.xml, bad-note1.xml, bad-note2.xml --> <rewriteURI uriStartString="http://stackoverflow.com/2014/09/xsd" rewritePrefix="./ArbitraryFolder/schemas" /> <!-- add a second catalog as a further test: XSL will be resolved through it --> <nextCatalog catalog="./ArbitraryFolder/catalog.xml" /> </catalog> 

XML data

Various test cases include the XSD indicated in the processing instructions or root nodes.

Scheme: processing instruction

A schema can be provided using the xml-model (PI) processing instruction. Save as ./Tests/good-notes2.xml :

 <?xml version="1.0" encoding="UTF-8"?> <!-- Associating Schemas with XML documents: http://www.w3.org/TR/xml-model/ --> <?xml-model type="application/xml" href="http://stackoverflow.com/2014/09/xsd/notes/notes.xsd"?> <note> <title>Shopping List</title> <date>2014-08-30</date> <body>headlight fluid, flamgrabblit, exhaust coil</body> </note> 

Schematic: Node Root

The schema can be provided in the root attributes of the document node. Save as ./Tests/good-notes3.xml :

 <?xml version="1.0" encoding="UTF-8"?> <!-- XML Schema Part 1: Structures: Schema-Related Markup in Documents Being Validated: http://www.w3.org/TR/xmlschema-1/#Instance_Document_Constructions --> <note xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://stackoverflow.com http://stackoverflow.com/2014/09/xsd/notes/notes.xsd"> <title>Shopping List</title> <date>2014-08-30</date> <body>Eggs, Milk, Carrots</body> </note> 

Failure Check

The following should fail (hyphens need dates); save as ./Tests/bad-note1.xml :

 <?xml version="1.0" encoding="UTF-8"?> <!-- Associating Schemas with XML documents: http://www.w3.org/TR/xml-model/ --> <?xml-model type="application/xml" href="http://stackoverflow.com/2014/09/xsd/notes/notes.xsd"?> <!-- FAILS SCHEMA: date is not valid; should use hyphens --> <note> <title>Shopping List</title> <date>20140830</date> <body>headlight fluid, flamgrabblit, exhaust coil</body> </note> 

Conversion

Save this as ./Tests/note-to-html.xsl :

 <?xml version="1.0" encoding="UTF-8"?> <xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:xs="http://www.w3.org/2001/XMLSchema" exclude-result-prefixes="xs" version="2.0"> <!-- is in the second catalog (../ArbitraryFolder/catalog.xml) --> <xsl:import href="http://stackoverflow.com/2014/09/xsl/notes/notes.xsl"/> </xsl:stylesheet> 

Custom folder

Any folder is a path to files on a computer that can be located anywhere in the file system. The location of these files may differ, for example, between production, development, and storage.

Catalog

Save this file as ./ArbitraryFolder/catalog.xml :

 <?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE catalog PUBLIC "-//OASIS//DTD XML Catalogs V1.1//EN" "http://www.oasis-open.org/committees/entity/release/1.1/catalog.dtd"> <catalog xmlns="urn:oasis:names:tc:entity:xmlns:xml:catalog"> <!-- catalog entry for all notes --> <rewriteURI uriStartString="http://stackoverflow.com/2014/09/xsl/" rewritePrefix="./XSL/"/> </catalog> 

Notes

In this example, there are two files for converting notes: notes.xsl and note-body.xsl. The first includes the second.

Note Style Sheet

Save this as ./ArbitraryFolder/XSL/notes/notes.xsl :

 <?xml version="1.0" encoding="UTF-8"?> <xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:xs="http://www.w3.org/2001/XMLSchema" exclude-result-prefixes="xs" version="2.0"> <!-- will not be in catalog (though it could be): by convention, absolute path is assumed to be part of static file structure --> <xsl:import href="note-body.xsl"/> <xsl:template match="/"> <html> <head> <title>A Note</title> </head> <body> <xsl:apply-templates/> </body> </html> </xsl:template> <xsl:template match="note"> <div> <xsl:apply-templates select="title, date, body"/> </div> </xsl:template> <xsl:template match="title"> <h1><xsl:value-of select="."/></h1> </xsl:template> <xsl:template match="date"> <p class="date"><xsl:value-of select="."/></p> </xsl:template> </xsl:stylesheet> 

Note. Body style sheet

Save this as ./ArbitraryFolder/XSL/notes/note-body.xsl :

 <?xml version="1.0" encoding="UTF-8"?> <xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:xs="http://www.w3.org/2001/XMLSchema" exclude-result-prefixes="xs" version="2.0"> <xsl:template match="body"> <p class="notebody"><xsl:value-of select="."/></p> </xsl:template> </xsl:stylesheet> 

Scheme

The last required file is a schema; save this as ./schemas/notes/notes.xsd :

 <?xml version="1.0" encoding="UTF-8"?> <xs:schema elementFormDefault="qualified" xmlns:xs="http://www.w3.org/2001/XMLSchema"> <xs:element name="note"> <xs:complexType> <xs:sequence> <xs:element name="title" type="xs:token"/> <xs:element name="date" type="xs:date"/> <xs:element name="body" type="xs:string"/> </xs:sequence> </xs:complexType> </xs:element> </xs:schema> 

Building

This section describes how to create a test application.

Libraries

You will need Saxon 9 (for XSLT2.0 documents), Xerces, Xalan, and the API Resolver:

 jaxen-1.1.6.jar resolver.jar saxon9he.jar serializer.jar xalan.jar xercesImpl.jar xml-apis.jar xsltc.jar 

Scenarios

Save as ./build.sh :

 #!/bin/bash javac -d bin -cp .:lib/* src/TestXSD.java 

Save as ./run.sh :

 #!/bin/bash java -cp .:bin:lib/* src.TestXSD Tests/note-to-html.xsl $1 

Compile

Use ./build.sh to compile the code.

Execute output

Run using:

 ./run.sh filename.xml 

Good test

Verify that a good note is being tested:

 ./run.sh Tests/good-note2.xml 

No mistakes.

Bad test

Verify that the date of the bad note is not validating:

 ./run.sh Tests/bad-note1.xml 

As expected, this causes the desired error:

 Exception in thread "main" org.xml.sax.SAXParseException; cvc-datatype-valid.1.2.1: '20140830' is not a valid value for 'date'. at org.apache.xerces.util.ErrorHandlerWrapper.createSAXParseException(Unknown Source) at org.apache.xerces.util.ErrorHandlerWrapper.error(Unknown Source) at org.apache.xerces.impl.XMLErrorReporter.reportError(Unknown Source) at org.apache.xerces.impl.XMLErrorReporter.reportError(Unknown Source) at org.apache.xerces.impl.XMLErrorReporter.reportError(Unknown Source) at org.apache.xerces.impl.xs.XMLSchemaValidator$XSIErrorReporter.reportError(Unknown Source) at org.apache.xerces.impl.xs.XMLSchemaValidator.reportSchemaError(Unknown Source) at org.apache.xerces.impl.xs.XMLSchemaValidator.elementLocallyValidType(Unknown Source) at org.apache.xerces.impl.xs.XMLSchemaValidator.processElementContent(Unknown Source) at org.apache.xerces.impl.xs.XMLSchemaValidator.handleEndElement(Unknown Source) at org.apache.xerces.impl.xs.XMLSchemaValidator.endElement(Unknown Source) at org.apache.xerces.jaxp.validation.DOMValidatorHelper.finishNode(Unknown Source) at org.apache.xerces.jaxp.validation.DOMValidatorHelper.validate(Unknown Source) at org.apache.xerces.jaxp.validation.DOMValidatorHelper.validate(Unknown Source) at org.apache.xerces.jaxp.validation.ValidatorImpl.validate(Unknown Source) at javax.xml.validation.Validator.validate(Validator.java:124) at src.TestXSD.main(TestXSD.java:103)