To that, you'll use a Document Type Definition (DTD) as you experiment with validation. In other words, the message is saying that you are trying to validate the document, but no DTD has been declared, because no It is important to recognize that the only reason an exception is thrown when the file fails validation is as a result of the error-handling code you entered in the early stages of this tutorial.
That code is reproduced below: In general, a SAX parsing error is a validation error, although we have seen that it can also be generated if the file specifies a version of XML that the parser is not prepared to handle.
In addition to the error handling you've already learned about, there is one error that can occur when you are configuring the parser for schema-based validation.
If the parser is not 1.2 compliant, and therefore does not support XML Schema, it could throw a The first attribute defines the XML Name Space (xmlns) prefix, "xsi", where "xsi" stands for "XML Schema Instance".
SAXParser is recommended if SAX parsing event notification is required in addition to validation with a schema.
DOMParser is recommended if the DOM tree structure of an XML document is required for random access and modification of the XML document.The second line specifies the schema to use for elements in the document that do not have a namespace prefix -- that is, for the elements you typically define in any simple, uncomplicated XML document.Note: You'll be learning about namespaces in Using Namespaces.In this section we shall validate the example XML document with XML schema document catalog.xsd, with the SAXParser class. Create a SAXParser object and set the validation mode of the SAXParser object to SCHEMA_VALIDATION, as shown in the following listing: Validates the complete XML document with an XML schema if the parser is able to find a schema.If the parser is not able find a schema or if the XML document does not conform to the schema, an error is raised.The thing to remember is that your application will not generate a validation exception unless you supply an error handler like the one above. I would like to configure it so that it doesn't validate the namespace or schema location information indicated in the incoming XML, but still attempts to validate the rest of the XML. At the moment, my validation fails immediately because the xmlns version number in the incoming XML doesn't match the one I'm using.They use a simple XML Schema definition to validate personnel data stored in an XML file.)Note: There are multiple schema-definition languages, including RELAX NG, Schematron, and the W3C "XML Schema" standard.(Even a DTD qualifies as a "schema", although it is the only one that does not use XML syntax to describe schema constraints.) However, "XML Schema" presents us with a terminology challenge.As discussed before, we have used an Input Source object because most SAX implementations are Input Source based.The procedure to obtain an XMLSchema object is shown in the following listing: XSDBuilder builder = new XSDBuilder(); Input Stream input Stream=new File Input Stream(new File("catalog.xsd")); Input Source input Source=new Input Source(input Stream); XMLSchema schema = builder.build(input Source); As in the previous section, define an error handling class, Custom Error Handler that extends Default Handler class.