private static Object findJarServiceProvider()

in jaxp-api-1.3/src/main/java/javax/xml/parsers/FactoryFinder.java [232:320]
48 lines of code
11 McCabe index (conditional complexity)

    private static Object findJarServiceProvider(String factoryId)
        throws ConfigurationError
    {

        String serviceId = "META-INF/services/" + factoryId;
        InputStream is = null;

        // First try the Context ClassLoader
        ClassLoader cl = SecuritySupport.getContextClassLoader();
        if (cl != null) {
            is = SecuritySupport.getResourceAsStream(cl, serviceId);

            // If no provider found then try the current ClassLoader
            if (is == null) {
                cl = FactoryFinder.class.getClassLoader();
                is = SecuritySupport.getResourceAsStream(cl, serviceId);
            }
        } else {
            // No Context ClassLoader, try the current
            // ClassLoader
            cl = FactoryFinder.class.getClassLoader();
            is = SecuritySupport.getResourceAsStream(cl, serviceId);
        }

        if (is == null) {
            // No provider found
            return null;
        }

        if (debug) dPrint("found jar resource=" + serviceId +
               " using ClassLoader: " + cl);

        // 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"), DEFAULT_LINE_LENGTH);
        } catch (java.io.UnsupportedEncodingException e) {
            rd = new BufferedReader(new InputStreamReader(is), DEFAULT_LINE_LENGTH);
        }
        
        String factoryClassName = null;
        try {
            // XXX Does not handle all possible input as specified by the
            // Jar Service Provider specification
            factoryClassName = rd.readLine();
        } 
        catch (IOException x) {
            // No provider found
            return null;
        }
        finally {
            try { 
                // try to close the reader. 
                rd.close(); 
            } 
            // Ignore the exception. 
            catch (IOException exc) {}
        }

        if (factoryClassName != null &&
            ! "".equals(factoryClassName)) {
            if (debug) dPrint("found in resource, value="
                   + factoryClassName);

        // Note: here we do not want to fall back to the current
        // ClassLoader because we want to avoid the case where the
        // resource file was found using one ClassLoader and the
        // provider class was instantiated using a different one.
        return newInstance(factoryClassName, cl, false);
        }

        // No provider found
        return null;
    }