static Object find(String factoryId,
    String fallbackClassName) throws ConfigurationError 
{
        debugPrintln("debug is on");
        ClassLoader classLoader = findClassLoader();
        // Use the system property first
        try {
            String systemProp =
                System.getProperty( factoryId );
            if( systemProp!=null) {
                debugPrintln("found system property " + systemProp);
                return newInstance(systemProp, classLoader);
            }
        } catch (SecurityException se) {
        }
        // try to read from $java.home/lib/xml.properties
        try {
            String javah=System.getProperty( "java.home" );
            String configFile = javah + File.separator +
                "lib" + File.separator + "jaxrpc.properties";
            File f=new File( configFile );
            if( f.exists()) {
                Properties props=new Properties();
                props.load( new FileInputStream(f));
                String factoryClassName = props.getProperty(factoryId);
                debugPrintln("found java.home property " + factoryClassName);
                return newInstance(factoryClassName, classLoader);
            }
        } catch(Exception ex ) {
            if( debug ) ex.printStackTrace();
        }
        String serviceId = "META-INF/services/" + factoryId;
        // try to find services in CLASSPATH
        try {
            InputStream is=null;
            if (classLoader == null) {
                is=ClassLoader.getSystemResourceAsStream( serviceId );
            } else {
                is=classLoader.getResourceAsStream( serviceId );
            }
            if( is!=null ) {
                debugPrintln("found " + serviceId);
                // Read the service provider name in UTF-8 as specified in
                // the jar spec.  Unfortunately this fails in Microsoft
                // VJ++, which does not implement the UTF-8
                // encoding. Theoretically, we should simply let it fail in
                // that case, since the JVM is obviously broken if it
                // doesn't support such a basic standard.  But since there
                // are still some users attempting to use VJ++ for
                // development, we have dropped in a fallback which makes a
                // second attempt using the platform's default encoding. In
                // VJ++ this is apparently ASCII, which is a subset of
                // UTF-8... and since the strings we'll be reading here are
                // also primarily limited to the 7-bit ASCII range (at
                // least, in English versions), this should work well
                // enough to keep us on the air until we're ready to
                // officially decommit from VJ++. [Edited comment from
                // jkesselm]
                BufferedReader rd;
                try {
                    rd = new BufferedReader(new InputStreamReader(is, "UTF-8"));
                } catch (java.io.UnsupportedEncodingException e) {
                    rd = new BufferedReader(new InputStreamReader(is));
                }
                String factoryClassName = rd.readLine();
                rd.close();
                if (factoryClassName != null &&
                    ! "".equals(factoryClassName)) {
                    debugPrintln("loaded from services: " + factoryClassName);
                    return newInstance(factoryClassName, classLoader);
                }
            }
        } catch( Exception ex ) {
            if( debug ) ex.printStackTrace();
        }
        if (fallbackClassName == null) {
            throw new ConfigurationError(
                "Provider for " + factoryId + " cannot be found", null);
        }
        debugPrintln("loaded from fallback value: " + fallbackClassName);
        return newInstance(fallbackClassName, classLoader);
}

Finds the implementation Class object in the specified order. Main entry point.