自定义ClassLoader对Class加密并解密

前言：本博客内容由张孝祥Java高新技术整理而来

class加密部分

项目目录结构

ClassLoaderAttach

package com.dao.chu.myloader;import java.util.Date;@SuppressWarnings("serial")public class ClassLoaderAttach extends Date{@Overridepublic String toString() {return "this is ClassLoaderAttach";}}

MyClassLoader

package com.dao.chu.myloader;import java.io.FileInputStream;import java.io.FileOutputStream;import java.io.IOException;import java.io.InputStream;import java.io.OutputStream;public class MyClassLoader {public static void main(String[] args) throws IOException {String srcPath = args[0];String destDir = args[1];String destFileName = srcPath.substring(srcPath.lastIndexOf("\\") + 1);String destFilePath = destDir + "\\" + destFileName;FileInputStream fin = new FileInputStream(srcPath);FileOutputStream fout = new FileOutputStream(destFilePath);cypher(fin,fout);fin.close();fout.close();}/*** <p>Title: cypher</p>* <p>Description:加密， 将原来的1改为0,0改为1</p>* @param in* @param out* @throws IOException */public static void cypher(InputStream in ,OutputStream out) throws IOException{int b=0;while ((b=in.read())!=-1) {out.write(b ^ 0xff);}}}

MyClassLoaderTest

package com.dao.chu.myloader;public class MyClassLoaderTest {public static void main(String[] args) {ClassLoaderAttach classLoaderAttach = new ClassLoaderAttach();System.out.println(classLoaderAttach.toString());}}

运行 MyClassLoader，输入ClassLoaderAttach.class的路径和要生成至的路径。

运行成功后可看到有加密后的class文件生成

执行MyClassLoaderTest，可看到正常输出

我们将加密的class文件与原来没加密过的class文件进行替换

再次执行MyClassLoaderTest，可看到报错信息。说明加密成功，用原来的类加载器不能运行，所以我们要用自己的类加载器运行

自定义ClassLoader部分

我们将MyClassLoader修改如下

package com.dao.chu.myloader;import java.io.ByteArrayOutputStream;import java.io.FileInputStream;import java.io.FileOutputStream;import java.io.IOException;import java.io.InputStream;import java.io.OutputStream;public class MyClassLoader extends ClassLoader{public static void main(String[] args) throws IOException {String srcPath = args[0];String destDir = args[1];String destFileName = srcPath.substring(srcPath.lastIndexOf("\\") + 1);String destFilePath = destDir + "\\" + destFileName;FileInputStream fin = new FileInputStream(srcPath);FileOutputStream fout = new FileOutputStream(destFilePath);cypher(fin,fout);fin.close();fout.close();}/*** <p>Title: cypher</p>* <p>Description:加密， 将原来的1改为0,0改为1</p>* @param in* @param out* @throws IOException */public static void cypher(InputStream in ,OutputStream out) throws IOException{int b=0;while ((b=in.read())!=-1) {out.write(b ^ 0xff);}}private String classDir;public MyClassLoader(){}public MyClassLoader(String classDir){this.classDir=classDir;}/** * 覆盖ClassLoader的findClass方法 */@SuppressWarnings("deprecation")@Overrideprotected Class<?> findClass(String name)throws ClassNotFoundException {String classFileName = classDir + "\\" + name + ".class";try {FileInputStream fin = new FileInputStream(classFileName);ByteArrayOutputStream baout = new ByteArrayOutputStream();//解密cypher(fin,baout);fin.close();//转为字节数组byte[] byteArray = baout.toByteArray();return defineClass(byteArray, 0, byteArray.length);} catch (Exception e) {}return null;}}

MyClassLoaderTest修改如下

package com.dao.chu.myloader;import java.util.Date;public class MyClassLoaderTest {@SuppressWarnings("rawtypes")public static void main(String[] args) throws ClassNotFoundException, InstantiationException, IllegalAccessException {//ClassLoaderAttach classLoaderAttach = new ClassLoaderAttach();//System.out.println(classLoaderAttach.toString());Class c = new MyClassLoader("myloaderlib").loadClass("ClassLoaderAttach");Date d = (Date)c.newInstance();System.out.println(d);}}

测试前我们需将原来生成的ClassLoaderAttach.class删掉，避免父类加载影响结果

最后执行MyClassLoaderTest

正是我们想要的结果