What s the best way to validate an XML file against an XSD file

Question

I m generating some xml files that needs to conform to an xsd file that was given to me   What s the best way to verify they conform

User · Accepted Answer

The Java runtime library supports validation. Last time I checked this was the Apache Xerces parser under the covers. You should probably use a javax.xml.validation.Validator.

import javax.xml.XMLConstants;
import javax.xml.transform.Source;
import javax.xml.transform.stream.StreamSource;
import javax.xml.validation.*;
import java.net.URL;
import org.xml.sax.SAXException;
//import java.io.File; // if you use File
import java.io.IOException;
...
URL schemaFile = new URL("http://host:port/filename.xsd");
// webapp example xsd: 
// URL schemaFile = new URL("http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd");
// local file example:
// File schemaFile = new File("/location/to/localfile.xsd"); // etc.
Source xmlFile = new StreamSource(new File("web.xml"));
SchemaFactory schemaFactory = SchemaFactory
    .newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);
try {
  Schema schema = schemaFactory.newSchema(schemaFile);
  Validator validator = schema.newValidator();
  validator.validate(xmlFile);
  System.out.println(xmlFile.getSystemId() + " is valid");
} catch (SAXException e) {
  System.out.println(xmlFile.getSystemId() + " is NOT valid reason:" + e);
} catch (IOException e) {}

The schema factory constant is the string http://www.w3.org/2001/XMLSchema which defines XSDs. The above code validates a WAR deployment descriptor against the URL http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd but you could just as easily validate against a local file.

You should not use the DOMParser to validate a document (unless your goal is to create a document object model anyway). This will start creating DOM objects as it parses the document - wasteful if you aren't going to use them.

User · Answer

We build our project using ant  so we can use the schemavalidate task to check our config files    lt schemavalidate gt        lt fileset dir    configdir   includes       xml    gt   lt  schemavalidate gt    Now naughty config files will fail our build   http   ant apache org manual Tasks schemavalidate html

User · Answer

With JAXB  you could use the code below        Test public void testCheckXmlIsValidAgainstSchema         logger info  Validating an XML file against the latest schema            MyValidationEventCollector vec   new MyValidationEventCollector         validateXmlAgainstSchema vec  inputXmlFileName  inputXmlSchemaName  inputXmlRootClass        assertThat vec getValidationErrors   isEmpty    is expectedValidationResult       private void validateXmlAgainstSchema final MyValidationEventCollector vec  final String xmlFileName  final String xsdSchemaName  final Class lt   gt  rootClass        try  InputStream xmlFileIs   Thread currentThread   getContextClassLoader   getResourceAsStream xmlFileName              final JAXBContext jContext   JAXBContext newInstance rootClass              Unmarshal the data from InputStream         final Unmarshaller unmarshaller   jContext createUnmarshaller             final SchemaFactory sf   SchemaFactory newInstance XMLConstants W3C XML SCHEMA NS URI           final InputStream schemaAsStream   Thread currentThread   getContextClassLoader   getResourceAsStream xsdSchemaName           unmarshaller setSchema sf newSchema new StreamSource schemaAsStream              unmarshaller setEventHandler vec            unmarshaller unmarshal new StreamSource xmlFileIs   rootClass  getValue       The Document class is the root object in the XML file you want to validate          for  String validationError   vec getValidationErrors                  logger trace validationError                   catch  final Exception e            logger error  The validation of the XML file     xmlFileName     failed     e            class MyValidationEventCollector implements ValidationEventHandler       private final List lt String gt  validationErrors       public MyValidationEventCollector             validationErrors   new ArrayList lt  gt                public List lt String gt  getValidationErrors             return Collections unmodifiableList validationErrors               Override     public boolean handleEvent final ValidationEvent event            String pattern    line  0   column  1   error message  2            String errorMessage   MessageFormat format pattern  event getLocator   getLineNumber    event getLocator   getColumnNumber                    event getMessage             if  event getSeverity      ValidationEvent FATAL ERROR                validationErrors add errorMessage                     return true     you collect the validation errors in a List and handle them later

User · Answer

Since this is a popular question  I will point out that java can also validate against  quot referred to quot  xsd s  for instance if the  xml file itself specifies XSD s in the header  using xsi schemaLocation or xsi noNamespaceSchemaLocation  or xsi for particular namespaces  ex   lt document xmlns xsi  quot http   www w3 org 2001 XMLSchema-instance quot    xsi noNamespaceSchemaLocation  quot http   www example com document xsd quot  gt         or schemaLocation  always a list of namespace to xsd mappings   lt document xmlns xsi  quot http   www w3 org 2001 XMLSchema-instance quot    xsi schemaLocation  quot http   www example com my namespace http   www example com document xsd quot  gt         The other answers work here as well  because the  xsd files  quot map quot  to the namespaces declared in the  xml file  because they declare a namespace  and if matches up with the namespace in the  xml file  you re good   But sometimes it s convenient to be able to have a custom resolver    From the javadocs   quot If you create a schema without specifying a URL  file  or source  then the Java language creates one that looks in the document being validated to find the schema it should use  For example  quot  SchemaFactory factory   SchemaFactory newInstance  quot http   www w3 org 2001 XMLSchema quot    Schema schema   factory newSchema     and this works for multiple namespaces  etc  The problem with this approach is that the xmlsns xsi is probably a network location  so it ll by default go out and hit the network with each and every validation  not always optimal  Here s an example that validates an XML file against any XSD s it references  even if it has to pull them from the network     public static void verifyValidatesInternalXsd String filename  throws Exception       InputStream xmlStream   new new FileInputStream filename       DocumentBuilderFactory factory   DocumentBuilderFactory newInstance        factory setValidating true       factory setNamespaceAware true       factory setAttribute  quot http   java sun com xml jaxp properties schemaLanguage quot                     quot http   www w3 org 2001 XMLSchema quot        DocumentBuilder builder   factory newDocumentBuilder        builder setErrorHandler new RaiseOnErrorHandler         builder parse new InputSource xmlStream        xmlStream close           public static class RaiseOnErrorHandler implements ErrorHandler       public void warning SAXParseException e  throws SAXException         throw new RuntimeException e             public void error SAXParseException e  throws SAXException         throw new RuntimeException e             public void fatalError SAXParseException e  throws SAXException         throw new RuntimeException e              You can avoid pulling referenced XSD s from the network  even though the xml files reference url s  by specifying the xsd manually  see some other answers here  or by using an  quot XML catalog quot  style resolver   Spring apparently also can intercept the URL requests to serve local files for validations   Or you can set your own via setResourceResolver  ex  Source xmlFile   new StreamSource xmlFileLocation   SchemaFactory schemaFactory   SchemaFactory                                  newInstance XMLConstants W3C XML SCHEMA NS URI   Schema schema   schemaFactory newSchema    Validator validator   schema newValidator    validator setResourceResolver new LSResourceResolver        Override   public LSInput resolveResource String type  String namespaceURI                                   String publicId  String systemId  String baseURI        InputSource is   new InputSource                             getClass   getResourceAsStream                             quot some local file in the jar xsd quot                                  or lookup by URI  etc        return new Input is      for class Input see                               https   stackoverflow com a 2342859 32453         validator validate xmlFile    See also here for another tutorial  I believe the default is to use DOM parsing  you can do something similar with SAX parser that is validating as well saxReader setEntityResolver your resolver here

User · Answer

Using Woodstox  configure the StAX parser to validate against your schema and parse the XML   If exceptions are caught the XML is not valid  otherwise it is valid      create the XSD schema from your schema file XMLValidationSchemaFactory schemaFactory   XMLValidationSchemaFactory newInstance XMLValidationSchema SCHEMA ID W3C SCHEMA   XMLValidationSchema validationSchema   schemaFactory createSchema schemaInputStream       create the XML reader for your XML file WstxInputFactory inputFactory   new WstxInputFactory    XMLStreamReader2 xmlReader    XMLStreamReader2  inputFactory createXMLStreamReader xmlInputStream    try          configure the reader to validate against the schema     xmlReader validateAgainst validationSchema           parse the XML     while  xmlReader hasNext              xmlReader next                  no exceptions  the XML is valid    catch  XMLStreamException e            exceptions  the XML is not valid    finally       xmlReader close        Note  If you need to validate multiple files  you should try to reuse your XMLInputFactory and XMLValidationSchema in order to maximize the performance

User · Answer

One more answer  since you said you need to validate files you are generating  writing   you might want to validate content while you are writing  instead of first writing  then reading back for validation  You can probably do that with JDK API for Xml validation  if you use SAX-based writer  if so  just link in validator by calling  Validator validate source  result    where source comes from your writer  and result is where output needs to go   Alternatively if you use Stax for writing content  or a library that uses or can use stax   Woodstox can also directly support validation when using XMLStreamWriter  Here s a blog entry showing how that is done

User · Answer

If you have a Linux-Machine you could use the free command-line tool SAXCount  I found this very usefull   SAXCount -f -s -n my xml   It validates against dtd and xsd  5s for a 50MB file   In debian squeeze it is located in the package  libxerces-c-samples    The definition of the dtd and xsd has to be in the xml  You can t config them separately

User · Answer

Here s how to do it using Xerces2  A tutorial for this  here  req  signup    Original attribution  blatantly copied from here   import org apache xerces parsers DOMParser  import java io File  import org w3c dom Document   public class SchemaTest     public static void main  String args            File docFile   new File  memory xml          try           DOMParser parser   new DOMParser            parser setFeature  http   xml org sax features validation   true           parser setProperty                http   apache org xml properties schema external-noNamespaceSchemaLocation                  memory xsd            ErrorChecker errors   new ErrorChecker            parser setErrorHandler errors           parser parse  memory xml           catch  Exception e            System out print  Problem parsing the file

User · Answer

Validate against online schemas  Source xmlFile   new StreamSource Thread currentThread   getContextClassLoader   getResourceAsStream  your xml     SchemaFactory factory   SchemaFactory newInstance XMLConstants W3C XML SCHEMA NS URI   Schema schema   factory newSchema Thread currentThread   getContextClassLoader   getResource  your xsd     Validator validator   schema newValidator    validator validate xmlFile     Validate against local schemas  Offline XML Validation with Java

User · Answer

Using Java 7 you can follow the documentation provided in package description      create a SchemaFactory capable of understanding WXS schemas SchemaFactory factory   SchemaFactory newInstance XMLConstants W3C XML SCHEMA NS URI       load a WXS schema  represented by a Schema instance Source schemaFile   new StreamSource new File  quot mySchema xsd quot     Schema schema   factory newSchema schemaFile       create a Validator instance  which can be used to validate an instance document Validator validator   schema newValidator        validate the DOM tree try       validator validate new StreamSource new File  quot instance xml quot       catch  SAXException e           instance document is invalid

User · Answer

I had to validate an XML against XSD just one time  so I tried XMLFox  I found it to be very confusing and weird  The help instructions didn t seem to match the interface   I ended up using LiquidXML Studio 2008  v6  which was much easier to use and more immediately familiar  the UI is very similar to Visual Basic 2008 Express  which I use frequently   The drawback  the validation capability is not in the free version  so I had to use the 30 day trial

User · Answer

If you are generating XML files programatically  you may want to look at the XMLBeans library  Using a command line tool  XMLBeans will automatically generate and package up a set of Java objects based on an XSD   You can then use these objects to build an XML document based on this schema   It has built-in support for schema validation  and can convert Java objects to an XML document and vice-versa   Castor and JAXB are other Java libraries that serve a similar purpose to XMLBeans

User · Answer

Are you looking for a tool or a library   As far as libraries goes  pretty much the de-facto standard is Xerces2 which has both C   and Java versions   Be fore warned though  it is a heavy weight solution  But then again  validating XML against XSD files is a rather heavy weight problem   As for a tool to do this for you  XMLFox seems to be a decent freeware solution  but not having used it personally I can t say for sure

[java] What's the best way to validate an XML file against an XSD file?

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