加载所有jar包下指定文件

加载所有jar包下指定文件：

如spring中加载 META-INF/spring.handlers 加载

---

org.springframework.core.io.support.PropertiesLoaderUtils#loadAllProperties(java.lang.String, java.lang.ClassLoader)

    /**
     * Load all properties from the specified class path resource
     * (in ISO-8859-1 encoding), using the given class loader.
     * <p>Merges properties if more than one resource of the same name
     * found in the class path.
     * @param resourceName the name of the class path resource
     * @param classLoader the ClassLoader to use for loading
     * (or {@code null} to use the default class loader)
     * @return the populated Properties instance
     * @throws IOException if loading failed
     */
    public static Properties loadAllProperties(String resourceName, @Nullable ClassLoader classLoader) throws IOException {
        Assert.notNull(resourceName, "Resource name must not be null");
        ClassLoader classLoaderToUse = classLoader;
        if (classLoaderToUse == null) {
            classLoaderToUse = ClassUtils.getDefaultClassLoader();
        }
        Enumeration<URL> urls = (classLoaderToUse != null ? classLoaderToUse.getResources(resourceName) :
                ClassLoader.getSystemResources(resourceName));
        Properties props = new Properties();
        while (urls.hasMoreElements()) {
            URL url = urls.nextElement();
            URLConnection con = url.openConnection();
            ResourceUtils.useCachesIfNecessary(con);
            InputStream is = con.getInputStream();
            try {
                if (resourceName.endsWith(XML_FILE_EXTENSION)) {
                    props.loadFromXML(is);
                }
                else {
                    props.load(is);
                }
            }
            finally {
                is.close();
            }
        }
        return props;
    }

事例：

    public static void main(String[] args) {
        String handlerMappingsLocation = "META-INF/spring.handlers";
        try {
            Properties properties = PropertiesLoaderUtils.loadAllProperties(handlerMappingsLocation, BeanUtil.class.getClassLoader());
            Enumeration<?> enumeration = properties.propertyNames();
            while (enumeration.hasMoreElements()) {
                String key = (String) enumeration.nextElement();
                System.out.println(key);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

核心语法:

ClassLoader.getSystemResources(resourceName)