// 系统类库路径
File libPath = new File(jar文件所在路径);// 获取所有的.jar和.zip文件
File[] jarFiles = libPath.listFiles(new FilenameFilter() {public boolean accept(File dir, String name) {return name.endsWith(".jar") || name.endsWith(".zip");}
});if (jarFiles != null) {// 从URLClassLoader类中获取类所在文件夹的方法// 对于jar文件，可以理解为一个存放class文件的文件夹Method method = URLClassLoader.class.getDeclaredMethod("addURL", URL.class);boolean accessible = method.isAccessible();     // 获取方法的访问权限try {if (accessible == false) {method.setAccessible(true);        // 设置方法的访问权限}// 获取系统类加载器URLClassLoader classLoader = (URLClassLoader) ClassLoader.getSystemClassLoader();for (File file : jarFiles) {URL url = file.toURI().toURL();try {method.invoke(classLoader, url);  LOG.debug("读取jar文件[name={}]", file.getName());} catch (Exception e) {LOG.error("读取jar文件[name={}]失败", file.getName());}}} finally {method.setAccessible(accessible);}
}

// 设置class文件所在根路径
// 例如/usr/java/classes下有一个test.App类，则/usr/java/classes即这个类的根路径，而.class文件的实际位置是/usr/java/classes/test/App.class
File clazzPath = new File(class文件所在根路径);// 记录加载.class文件的数量
int clazzCount = 0;if (clazzPath.exists() && clazzPath.isDirectory()) {// 获取路径长度int clazzPathLen = clazzPath.getAbsolutePath().length() + 1;Stack<File> stack = new Stack<>();stack.push(clazzPath);// 遍历类路径while (stack.isEmpty() == false) {File path = stack.pop();File[] classFiles = path.listFiles(new FileFilter() {public boolean accept(File pathname) {return pathname.isDirectory() || pathname.getName().endsWith(".class");}});for (File subFile : classFiles) {if (subFile.isDirectory()) {stack.push(subFile);} else {if (clazzCount++ == 0) {Method method = URLClassLoader.class.getDeclaredMethod("addURL", URL.class);boolean accessible = method.isAccessible();try {if (accessible == false) {method.setAccessible(true);}// 设置类加载器URLClassLoader classLoader = (URLClassLoader) ClassLoader.getSystemClassLoader();// 将当前类路径加入到类加载器中method.invoke(classLoader, clazzPath.toURI().toURL());} finally {method.setAccessible(accessible);}}// 文件名称String className = subFile.getAbsolutePath();className = className.substring(clazzPathLen, className.length() - 6);className = className.replace(File.separatorChar, '.');// 加载Class类Class.forName(className);LOG.debug("读取应用程序类文件[class={}]", className);}}}
}