How to create XML validator(验证器；验证程序) from XML schema

In order to check XML data for validity we have to prepare its schema XSD-file. This file will be loaded by a JAXP package to a Schema objects instance. Then we‘ll use Schema to produce Validator which can then be used to validate any document with type defined in outr schema.

import javax.xml.transform.stream.StreamSource;
import javax.xml.validation.Schema;
import javax.xml.validation.SchemaFactory;
import javax.xml.validation.Validator;

import org.xml.sax.SAXException;

/**
 * A sample application which shows how to perform a XML document validation.
 */

public class Test {
    public static void main(String[] args) {
        try {
            // define the type of schema - we use W3C:
            String schemaLang = "http://www.w3.org/2001/XMLSchema";

            // get validation driver:
            SchemaFactory factory = SchemaFactory.newInstance(schemaLang);

            // create schema by reading it from an XSD file:
            Schema schema = factory.newSchema(new StreamSource("contacts.xsd"));
            Validator validator = schema.newValidator();

            // at last perform validation:
            validator.validate(new StreamSource("contacts.xml"));

        } catch (SAXException ex) {
            // we are here if the document is not valid:
            System.out.println(ex.getMessage());
            // ... process validation error...
        } catch (Exception ex) {
            ex.printStackTrace();
        }
    }
}