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public class EasyTest {

      public void print(){

            System.out.println("EasyTest,you did it!");

      }

}

package cn.itcast.cc.cipher;

import java.io.*;

import java.security.Key;

import javax.crypto.*;

public class MyCipher {

      private Key key = null;

      private String traninfo = null;

      public MyCipher(Key key, String traninfo) {

            this.key = key;

            this.traninfo = traninfo;

      }

      public void cipher(InputStream ins, OutputStream ous) throws IOException {

            // 創(chuàng)建加密輸出流

            Cipher cip = null;

            CipherOutputStream cos = null;

            try {

                  cip = Cipher.getInstance(this.traninfo);

                  cip.init(Cipher.ENCRYPT_MODE, this.key);

                  cos = new CipherOutputStream(ous, cip);

                  // 寫(xiě)出到輸入流

                  int len = 0;

                  byte[] buf = new byte[1024];

                  while ((len = ins.read(buf)) != -1) {

                        cos.write(buf, 0, len);

                  }

            } catch (Exception e) {

                  e.printStackTrace();

            } finally {

                  // 釋放輸入和輸出流

                  cos.close();

                  ins.close();

                  ous.close();

            }

      }

}

package cn.itcast.cc.classloader;

import java.io.*;

import java.security.Key;

import javax.crypto.*;

public class MyClassLoader extends ClassLoader {

      private Key key = null;

      private String traninfo = null;

      public MyClassLoader(Key key, String traninfo) {

            this.key = key;

            this.traninfo = traninfo;

      }

      @Override

      @SuppressWarnings("unchecked")

      protected Class findClass(String name) throws ClassNotFoundException {

            // 獲取class解密后的字節(jié)碼

            byte[] classBytes = null;

            try {

                  classBytes = loadClassBytes(name);

            } catch (Exception e) {

                  throw new ClassNotFoundException(name);

            }

            // 使用字節(jié)碼，實(shí)例類對(duì)象

            String clname = name.substring(name.lastIndexOf("/") + 1, name

                        .lastIndexOf("."));

            Class cl = defineClass(clname, classBytes, 0, classBytes.length);

            if (cl == null)

                  throw new ClassNotFoundException(name);

            return cl;

      }

      private byte[] loadClassBytes(String name) throws IOException {

            // 讀入文件

            FileInputStream ins = null;

            ByteArrayOutputStream baos = null;

            CipherInputStream cis = null;

            byte[] result = null;

            try {

                  ins = new FileInputStream(name);

                  Cipher cip = Cipher.getInstance(this.traninfo);

                  cip.init(Cipher.DECRYPT_MODE, this.key);

                  // 使用密碼解密class文件

                  cis = new CipherInputStream(ins, cip);

                  baos = new ByteArrayOutputStream();

                  int len = 0;

                  byte[] buf = new byte[1024];

                  while ((len = cis.read(buf)) != -1) {

                        baos.write(buf, 0, len);

                  }

                  result = baos.toByteArray();

            } catch (Exception e) {

                  e.printStackTrace();

            } finally {

                  // 釋放流

                  baos.close();

                  cis.close();

                  ins.close();

            }

            return result;

      }

}

package cn.itcast.cc.testcalss;

import java.io.*;

import java.lang.reflect.Method;

import java.security.Key;

import javax.crypto.KeyGenerator;

import cn.itcast.cc.cipher.MyCipher;

import cn.itcast.cc.classloader.MyClassLoader;

public class Test {

      public static void main(String[] args) {

            KeyGenerator keyGen;

            try {

                  // 創(chuàng)建密鑰

                  keyGen = KeyGenerator.getInstance("AES");

                  keyGen.init(128);

                  Key key = keyGen.generateKey();

                  keyGen = null;

                  MyCipher mc = new MyCipher(key,"AES/ECB/PKCS5Padding");

                  mc.cipher(new FileInputStream(new File("C:/EasyTestbak.class")),

                              new FileOutputStream(new File("C:/EasyTest.class")));

                  MyClassLoader mcl = new MyClassLoader(key,"AES/ECB/PKCS5Padding");

                  Class clazz = mcl.loadClass("C:/EasyTest.class");

                  Method meth = clazz.getMethod("print", null);

                  meth.invoke(clazz.newInstance(), null);

            } catch (Exception e1) {

                  e1.printStackTrace();

            }

      }

}