扫描可从上下文类加载器访问的所有类，这些类属于给定的包和子包。

/** 
 来自 n o w j a   v  a . c o m - 时  代  Java**/

//package com.nowjava;

import java.io.File;

import java.net.URL;

import java.util.ArrayList;

import java.util.Enumeration;

import java.util.List;

import java.util.TreeSet;

import java.util.zip.ZipEntry;

import java.util.zip.ZipInputStream;


public class Main {



    /**

     * Scans all classes accessible from the context class loader which belong

     * to the given package and sub packages. Adapted from

     * http://snippets.dzone.com/posts/show/4831 and extended to support use of

     * JAR files

     * 

     * @param packageName The base package

     * @return The classes

     * @throws Exception

     */

    public static List<Class<?>> getClasses(String packageName)/**来自 时 代 J a v a - N o w J a v a . c o m**/

            throws Exception {

        String path = packageName.replace('.', '/');

        ClassLoader classLoader = Thread.currentThread()

                .getContextClassLoader();

        assert classLoader != null;

        Enumeration<URL> resources = classLoader.getResources(path);

        List<String> dirs = new ArrayList<String>();

        while (resources.hasMoreElements()) {

            URL resource = resources.nextElement();

            dirs.add(resource.getFile());

        }

        TreeSet<String> classes = new TreeSet<String>();

        for (String directory : dirs) {

            classes.addAll(findClasses(directory, packageName));

        }

        ArrayList<Class<?>> classList = new ArrayList<Class<?>>();

        for (String clazz : classes) {

            classList.add(Class.forName(clazz));

        }


        return classList;

    }


    /**

     * Recursive method used to find all classes in a given directory and

     * subdirs. Adapted from http://snippets.dzone.com/posts/show/4831 and

     * extended to support use of JAR files

     * 

     * @param directory The base directory

     * @param packageName The package name for classes found inside the base

     *            directory

     * @return The classes

     * @throws ClassNotFoundException

     */

    private static TreeSet<String> findClasses(String directory,

            String packageName) throws Exception {

        TreeSet<String> classes = new TreeSet<String>();

        if (directory.startsWith("file:") && directory.contains("!")) {

            String[] split = directory.split("!");

            URL jar = new URL(split[0]);

            try (ZipInputStream zip = new ZipInputStream(jar.openStream())) {

                ZipEntry entry = null;

                while ((entry = zip.getNextEntry()) != null) {

                    if (entry.getName().endsWith(".class")) {

                        String className = entry.getName()

                                .replaceAll("[$].*", "")

                                .replaceAll("[.]class", "")

                                .replace('/', '.');

                        if (className.startsWith(packageName)) {

                            classes.add(className);

                        }

                    }

                }

            }

        }

        File dir = new File(directory);

        if (!dir.exists()) {

            return classes;

        }

        File[] files = dir.listFiles();

        if (files