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) {
  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(); // 获得当前的包名
   try {
    List<Class> allClass = getClasses(packageName); // 获得当前包下以及子包下的所有类
    // 判断是否是同一个接口
    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))) { // 本身不加进去
       returnClassList.add(allClass.get(i));
      }
     }
    }
   } catch (ClassNotFoundException e) {
    e.printStackTrace();
   } catch (IOException e) {
    e.printStackTrace();
   }
  }
  return returnClassList;
 }

 // 从一个包中查找出所有的类，在jar包中不能查找
 private static List<Class> getClasses(String packageName)
   throws ClassNotFoundException, IOException {
  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;
 }
}