public abstract class SpringFactoriesLoader {

    /** The location to look for the factories. Can be present in multiple JAR files. */

    private static final String FACTORIES_RESOURCE_LOCATION = "META-INF/spring.factories";

    private static final Log logger = LogFactory.getLog(SpringFactoriesLoader.class);

    /**

     * Loads the factory implementations of the given type from the default location, using

     * the given class loader.

     * <p>The returned factories are ordered in accordance with the {@link OrderComparator}.

     * @param factoryClass the interface or abstract class representing the factory

     * @param classLoader the ClassLoader to use for loading (can be {@code null} to use the default)

     */

    public static <T> List<T> loadFactories(Class<T> factoryClass, ClassLoader classLoader) {

        Assert.notNull(factoryClass, "'factoryClass' must not be null");

        if (classLoader == null) {

            classLoader = SpringFactoriesLoader.class.getClassLoader();

        }

        List<String> factoryNames = loadFactoryNames(factoryClass, classLoader);

        if (logger.isTraceEnabled()) {

            logger.trace("Loaded [" + factoryClass.getName() + "] names: " + factoryNames);

        }

        List<T> result = new ArrayList<T>(factoryNames.size());

        for (String factoryName : factoryNames) {

            result.add(instantiateFactory(factoryName, factoryClass, classLoader));

        }

        OrderComparator.sort(result);

        return result;

    }

    private static List<String> loadFactoryNames(Class<?> factoryClass, ClassLoader classLoader) {

        String factoryClassName = factoryClass.getName();

        try {

            List<String> result = new ArrayList<String>();

            Enumeration<URL> urls = classLoader.getResources(FACTORIES_RESOURCE_LOCATION);

            while (urls.hasMoreElements()) {

                URL url = urls.nextElement();

                Properties properties = PropertiesLoaderUtils.loadProperties(new UrlResource(url));

                String factoryClassNames = properties.getProperty(factoryClassName);

                result.addAll(Arrays.asList(StringUtils.commaDelimitedListToStringArray(factoryClassNames)));

            }

            return result;

        }

        catch (IOException ex) {

            throw new IllegalArgumentException("Unable to load [" + factoryClass.getName() +

                    "] factories from location [" + FACTORIES_RESOURCE_LOCATION + "]", ex);

        }

    }

    @SuppressWarnings("unchecked")

    private static <T> T instantiateFactory(String instanceClassName, Class<T> factoryClass, ClassLoader classLoader) {

        try {

            Class<?> instanceClass = ClassUtils.forName(instanceClassName, classLoader);

            if (!factoryClass.isAssignableFrom(instanceClass)) {

                throw new IllegalArgumentException(

                        "Class [" + instanceClassName + "] is not assignable to [" + factoryClass.getName() + "]");

            }

            return (T) instanceClass.newInstance();

        }

        catch (Throwable ex) {

            throw new IllegalArgumentException("Cannot instantiate factory class: " + factoryClass.getName(), ex);

        }

    }