由一个接口找他实现类(ClassUtils)

import java.io.File; import java.io.IOException; import java.net.URL; import java.util.ArrayList; import java.util.Enumeration; import java.util.List; public class ClassUtils { public static List<Class> getAllClassByInterface(Class c) { // 给一个接口，返回这个接口的所有实现类 List<Class> returnClassList = new ArrayList<Class>();// 返回结果 // 如果不是一个接口，则不做处理 if (c.isInterface()) { String packageName = c.getPackage().getName();// 获得当前包名 try { List<Class> allClass = getClasses(packageName);// 获得当前包下以及包下的所有类 for (int i = 0; i < allClass.size(); i++) { if (c.isAssignableFrom(allClass.get(i))) {// 判断是不是一个接口 if (!c.equals(allClass.get(i))) {// 本身加不进去 returnClassList.add(allClass.get(i)); } } } } catch (ClassNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IOException e) { // TODO: handle exception e.printStackTrace(); } } return returnClassList; } // 从一个包中查找出所有类,在jar包中不能查找 private static List<Class> getClasses(String packageName) throws IOException, ClassNotFoundException { ClassLoader classLoader = Thread.currentThread() .getContextClassLoader(); String path = packageName.replace('.', '/'); Enumeration<URL> resources = classLoader.getResources(path); List<File> dirs = new ArrayList<File>(); while (resources.hasMoreElements()) { URL resource = resources.nextElement(); dirs.add(new File(resource.getFile())); } ArrayList<Class> classes = new ArrayList<Class>(); for (File directory : dirs) { classes.addAll(findClasses(directory, packageName)); } return classes; } private static List<Class> findClasses(File directory, String packageName) throws ClassNotFoundException { List<Class> classes = new ArrayList<Class>(); if (!directory.exists()) { return classes; } File[] files = directory.listFiles(); for (File file : files) { if (file.isDirectory()) { assert !file.getName().contains("."); classes.addAll(findClasses(file, packageName + '.' + file.getName())); } else if (file.getName().endsWith(".class")) { classes.add(Class.forName(packageName + "." + file.getName().substring(0, file.getName().length() - 6))); } } return classes; } }