package com.ctc.wstx.compat;

import java.util.logging.Logger;

import javax.xml.namespace.QName;

Helper class used to solve [WSTX-174]: some older AppServers were
shipped with incompatible version of QName class, which is missing
the 3 argument constructor. To address this, we'll use bit of
ClassLoader hacker to gracefully (?) downgrade to using 2 arg
alternatives if necessary.

Note: choice of java.util.logging logging is only based on the
fact that it is guaranteed to be present (we have JDK 1.4 baseline
requirement) so that we do not add external dependencies.
It is not a recommendation for using JUL per se; most users would
do well to just use slf4j or log4j directly instead.
Author:
Tatu Saloranta
Since:
3.2.8/**
 * Helper class used to solve [WSTX-174]: some older AppServers were
 * shipped with incompatible version of QName class, which is missing
 * the 3 argument constructor. To address this, we'll use bit of
 * ClassLoader hacker to gracefully (?) downgrade to using 2 arg
 * alternatives if necessary.
 *<p>
 * Note: choice of java.util.logging logging is only based on the
 * fact that it is guaranteed to be present (we have JDK 1.4 baseline
 * requirement) so that we do not add external dependencies.
 * It is not a recommendation for using JUL per se; most users would
 * do well to just use slf4j or log4j directly instead.
 *
 * @author Tatu Saloranta
 * 
 * @since 3.2.8
 */
public final class QNameCreator
{
    
Creator object that creates QNames using proper 3-arg constructor.
If dynamic class loading fails
/**
     * Creator object that creates QNames using proper 3-arg constructor.
     * If dynamic class loading fails
     */
    private final static Helper _helper;
    static {
        Helper h = null;
        try {
            // Not sure where it'll fail, constructor or create...
            Helper h0 = new Helper();
            /*QName n =*/ h0.create("elem", "http://dummy", "ns");
            h = h0;
        } catch (Throwable t) {
            String msg = "Could not construct QNameCreator.Helper; assume 3-arg QName constructor not available and use 2-arg method instead. Problem: "+t.getMessage();
            try {
                Logger.getLogger("com.ctc.wstx.compat.QNameCreator").warning(msg);
            } catch (Throwable t2) { // just in case JUL craps out...
                System.err.println("ERROR: failed to log error using Logger (problem "+t.getMessage()+"), original problem: "+msg);
            }
        }
        _helper = h;
    }

    public static QName create(String uri, String localName, String prefix)
    {
        if (_helper == null) { // can't use 3-arg constructor; but 2-arg will be there
            return new QName(uri, localName);
        }
        return _helper.create(uri, localName, prefix);
    }

    
Helper class used to encapsulate calls to the missing method.
/**
     * Helper class used to encapsulate calls to the missing method.
     */
    private final static class Helper
    {
        public Helper() { }
        
        public QName create(String localName, String nsURI, String prefix)
        {
            return new QName(localName, nsURI, prefix);
        }
    }
}