public static Properties loadProperties()

in dubbo-common/src/main/java/org/apache/dubbo/common/utils/ConfigUtils.java [211:307]
88 lines of code
13 McCabe index (conditional complexity)

    public static Properties loadProperties(
            Set<ClassLoader> classLoaders, String fileName, boolean allowMultiFile, boolean optional) {
        Properties properties = new Properties();
        // add scene judgement in windows environment Fix 2557
        if (checkFileNameExist(fileName)) {
            try {
                FileInputStream input = new FileInputStream(fileName);
                try {
                    properties.load(input);
                } finally {
                    input.close();
                }
            } catch (Throwable e) {
                logger.warn(
                        COMMON_IO_EXCEPTION,
                        "",
                        "",
                        "Failed to load " + fileName + " file from " + fileName + "(ignore this file): "
                                + e.getMessage(),
                        e);
            }
            return properties;
        }

        Set<java.net.URL> set = null;
        try {
            List<ClassLoader> classLoadersToLoad = new LinkedList<>();
            classLoadersToLoad.add(ClassUtils.getClassLoader());
            classLoadersToLoad.addAll(classLoaders);
            set = ClassLoaderResourceLoader.loadResources(fileName, classLoadersToLoad).values().stream()
                    .reduce(new LinkedHashSet<>(), (a, i) -> {
                        a.addAll(i);
                        return a;
                    });
        } catch (Throwable t) {
            logger.warn(COMMON_IO_EXCEPTION, "", "", "Fail to load " + fileName + " file: " + t.getMessage(), t);
        }

        if (CollectionUtils.isEmpty(set)) {
            if (!optional) {
                logger.warn(COMMON_IO_EXCEPTION, "", "", "No " + fileName + " found on the class path.");
            }
            return properties;
        }

        if (!allowMultiFile) {
            if (set.size() > 1) {
                String errMsg = String.format(
                        "only 1 %s file is expected, but %d dubbo.properties files found on class path: %s",
                        fileName, set.size(), set);
                logger.warn(COMMON_IO_EXCEPTION, "", "", errMsg);
            }

            // fall back to use method getResourceAsStream
            try {
                properties.load(ClassUtils.getClassLoader().getResourceAsStream(fileName));
            } catch (Throwable e) {
                logger.warn(
                        COMMON_IO_EXCEPTION,
                        "",
                        "",
                        "Failed to load " + fileName + " file from " + fileName + "(ignore this file): "
                                + e.getMessage(),
                        e);
            }
            return properties;
        }

        logger.info("load " + fileName + " properties file from " + set);

        for (java.net.URL url : set) {
            try {
                Properties p = new Properties();
                InputStream input = url.openStream();
                if (input != null) {
                    try {
                        p.load(input);
                        properties.putAll(p);
                    } finally {
                        try {
                            input.close();
                        } catch (Throwable t) {
                        }
                    }
                }
            } catch (Throwable e) {
                logger.warn(
                        COMMON_IO_EXCEPTION,
                        "",
                        "",
                        "Fail to load " + fileName + " file from " + url + "(ignore this file): " + e.getMessage(),
                        e);
            }
        }

        return properties;
    }