技術標籤：java工具類java

通過一個介面查詢實現該介面的所有的實現類【工具包ClassUtils】

public class ClassUtils {
    // 給一個介面，返回所有介面的實現類
    public static List<Class> getAllClassByInterface(Class c) throws Exception {
        List<Class> resultClassList = new ArrayList<>();    // 返回結果
        if (c.isInterface()) {  // 判斷是否為介面
            String name = c.getPackage().getName(); // 獲取當前包名
                List<Class> allClass =getClass(name);
            for (int i = 0; i < allClass.size(); i++) {
                if (c.isAssignableFrom(allClass.get(i))) {
                    if (!c.equals(allClass.get(i))) {
                        resultClassList.add(allClass.get(i));
                    }
                }
            }
        } else {
            System.out.println("該Class不是一個介面");
        }
        return resultClassList;
    }

    private static List<Class> getClass(String name) throws Exception {
        ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
        String path = name.replace(".", "/");
        Enumeration<URL> resources = classLoader.getResources(path);
        List<File> fileList = new ArrayList<>();
        while (resources.hasMoreElements()) {
            URL url = resources.nextElement();
            fileList.add(new File(url.getFile()));
        }
        List<Class> classes = new ArrayList<>();
        for (File directory : fileList) {
            classes.addAll(findClasses(directory, name));
        }
        return classes;
    }

    private static List<Class> findClasses(File directory, String name) throws Exception {
        List<Class> classes = new ArrayList<>();
        if (!directory.exists()) {
            return classes;
        }
        File[] files = directory.listFiles();
        for (File file : files) {
            if (file.isDirectory()) {
                assert !file.getName().contains(".");
                classes.addAll(findClasses(file, name + "." +
                        file.getName()));
            } else if (file.getName().endsWith(".class")) {
                classes.add(Class.forName(name + '.' +
                        file.getName().substring(0, file.getName().length() - 6)));
            }
        }

        return classes;
    }


}