ClassLoader

import java.util.Date;

public class ClassLoaderTest {

 /**
  * @param args
  */
 public static void main(String[] args) throws Exception {
  // TODO Auto-generated method stub
  System.out.println(
    ClassLoaderTest.class.getClassLoader().getClass().getName()
    );
  System.out.println(
    System.class.getClassLoader()
    );
  System.out.println("xxx");
  ClassLoader loader = ClassLoaderTest.class.getClassLoader();
  while(loader != null){
   System.out.println(loader.getClass().getName());
   loader = loader.getParent();
  }
  System.out.println(loader);
  
  //System.out.println(new ClassLoaderAttachment().toString());
  System.out.println("xxx2");
  Class clazz = new MyClassLoader("itcastlib").loadClass("cn.itcast.day2.ClassLoaderAttachment");
  Date d1 =  (Date)clazz.newInstance();
  System.out.println(d1);
 }

}

 

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import java.util.Date;

public class ClassLoaderAttachment extends Date {
 public String toString(){
  return "hello,itcast";
 }
}

-------------------------------------------------

import java.io.ByteArrayOutputStream;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;

public class MyClassLoader extends ClassLoader{

 /**
  * @param args
  */
 public static void main(String[] args) throws Exception {
  // TODO Auto-generated method stub
  String srcPath = args[0];
  String destDir = args[1];
  FileInputStream fis = new FileInputStream(srcPath);
  String destFileName = srcPath.substring(srcPath.lastIndexOf('\\')+1);
  String destPath = destDir + "\\" + destFileName;
  FileOutputStream fos = new FileOutputStream(destPath);
  cypher(fis,fos);
  fis.close();
  fos.close();
 }
 
 private static void cypher(InputStream ips ,OutputStream ops) throws Exception{
  int b = -1;
  while((b=ips.read())!=-1){
   ops.write(b ^ 0xff);
  }
 }

 private String classDir;

 @Override
 protected Class<?> findClass(String name) throws ClassNotFoundException {
  // TODO Auto-generated method stub
  String classFileName = classDir + "\\"  + name.substring(name.lastIndexOf('.')+1) + ".class";
  try {
   FileInputStream fis = new FileInputStream(classFileName);
   ByteArrayOutputStream  bos = new ByteArrayOutputStream();
   cypher(fis,bos);
   fis.close();
   System.out.println("aaa");
   byte[] bytes = bos.toByteArray();
   return defineClass(bytes, 0, bytes.length);
  } catch (Exception e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }
  return null;
 }
 
 public MyClassLoader(){
  
 }
 
 public MyClassLoader(String classDir){
  this.classDir = classDir;
 }
}