Anybody know how to read "xerces"?? and a lot more......

Question

And, what's the relationship between xerces and sun's JAXP? Is jaxp more a interface less an implementation? I found jaxp calls some part of xerces pack. Meanwhile, in xerces pack there sits a jaxp pack. Xerces say it support jaxp, so, is that mean xerces is a implementation of jaxp interface?
Both of the two pack contains some implementation..... I'm confused.
Can anybody give me an insider's view of jaxp package?
"The SAX Plugability classes allow an application programmer to provide an implementation of the
org.xml.sax.DefaultHandler API to a SAXParser implementation and parse XML documents. As the parser processes the XML document, it will call methods on the provided DefaultHandler."
------from jaxp1.2 spec
I'm sorry but English isn't my mother tongue. I'm rather confused by the statements above. Anybody do me a favour to translate it to plain English? Very much thanks.
Also, what does the following code mean? (from javax.xml.parser.SAXParserFactory.java)
class FactoryFinder is in nowhere to be found. Can anybody help explain it?
    public static SAXParserFactory newInstance()
        throws FactoryConfigurationError
        try {
            return (SAXParserFactory) FactoryFinder.find(
                /* The default property name according to the JAXP spec */
                "javax.xml.parsers.SAXParserFactory",
                /* The fallback implementation class name */
                "org.apache.crimson.jaxp.SAXParserFactoryImpl"); //what's this??
        } catch (FactoryFinder.ConfigurationError e) {
            throw new FactoryConfigurationError(e.getException(),
                                                e.getMessage());
    }Moreover, what the relation between SAXParserFactoryImpl and SAXParserFactory?
I wrote a program to validate xml files against dtd or schema. Does the package automatically find dtd or schema files within the xml or i have to offer them in the command line? In my case, it seems to be the latter.

Answer 1

Well, you see, my real problem is that i coded to validate a xml file against xsd or dtd. However, I have to feed the program with a dtd or xsd file in the command line to make it work. Isn't it supposed to find out a proper dtd/xsd in the xml file(when specified)? Or I it isn't properly configured?
Help me, please!
Here is the code:
package xmltool;
import javax.xml.parsers.*;
import org.xml.sax.*;
import org.xml.sax.helpers.*;
import java.io.*;
* This class validate a xml file against its DTD or Schema.
* @version 1.1
* @auther Data Zoe
public class Check extends DefaultHandler
    /** Constants used for JAXP 1.2 */
    static final String JAXP_SCHEMA_LANGUAGE =
        "http://java.sun.com/xml/jaxp/properties/schemaLanguage";
    static final String W3C_XML_SCHEMA =
        "http://www.w3.org/2001/XMLSchema";
     public static void main(String args[])throws Exception
          //tag varible
          boolean dtdValidate = false;
          boolean xsdValidate = false;
          //xml file to be validated
          String fileName = null;
          //Check input
          for(int i=0;i<args.length;i++)
                    if(args.endsWith(".xml")||args[i].endsWith(".XML"))
                         fileName = args[i];
                    else if(args[i].endsWith(".xsd")||args[i].endsWith(".XSD"))
                         xsdValidate = true;
                    else if(args[i].endsWith(".dtd")||args[i].endsWith(".DTD"))
                         dtdValidate = true;
                    else
                              System.err.println("Out put usage infomation.");
          if(fileName!=null)
               SAXParserFactory spf = SAXParserFactory.newInstance();
               spf.setNamespaceAware(true);
               spf.setValidating(dtdValidate||xsdValidate);
               SAXParser saxParser = spf.newSAXParser();
               XMLReader xmlReader = saxParser.getXMLReader();
               xmlReader.setContentHandler(new Check());
               xmlReader.setErrorHandler(new myErrorHandler(System.err));
               xmlReader.parse(fileName);
               if (xsdValidate)
                    try     {saxParser.setProperty(JAXP_SCHEMA_LANGUAGE, W3C_XML_SCHEMA);}
                    catch (SAXNotRecognizedException x)
                              // This can happen if the parser does not support JAXP 1.2
                              System.err.println(
                                   "Error: JAXP SAXParser property not recognized: "
                                   + JAXP_SCHEMA_LANGUAGE);
                              System.err.println(
                                   "Check to see if parser conforms to JAXP 1.2 spec.");
                              System.exit(1);
          else
               System.err.println("No xml file to validate");
     * Error handler
     private static class myErrorHandler implements ErrorHandler
          /** Error handler output goes here */
          private PrintStream out;
          myErrorHandler(PrintStream out)
               this.out = out;
          * Returns a string describing parse exception details
          private String getParseExceptionInfo(SAXParseException spe)
               String systemId = spe.getSystemId();
               if (systemId == null)
                    systemId = "null";
               String info = "URI=" + systemId +
                    " Line=" + spe.getLineNumber() +
                    ": " + spe.getMessage();
               return info;
          // The following methods are standard SAX ErrorHandler methods.
          // See SAX documentation for more info.
          public void warning(SAXParseException spe) throws SAXException
               out.println("Warning: " + getParseExceptionInfo(spe));
          public void error(SAXParseException spe) throws SAXException
               String message = "Error: " + getParseExceptionInfo(spe);
               throw new SAXException(message);
          public void fatalError(SAXParseException spe) throws SAXException
               String message = "Fatal Error: " + getParseExceptionInfo(spe);
               throw new SAXException(message);