第8单元：类加载器的深入讲解与应用

44.类加载器及其委托机制的深入分析

package java_5;

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

public class MyClassLoader extends ClassLoader {
    static String srcPath;
    static String destPath;

    public static void main(String[] args) throws Exception {
          srcPath = args[0];
          destPath = args[1];
         InputStream in = new FileInputStream(srcPath );
          srcPath = srcPath .substring(0, srcPath.lastIndexOf('\\' ) - 6);
         OutputStream out = new FileOutputStream(srcPath + "\\" + destPath
                 + ".class");
         ClassLoader cl = MyClassLoader.class .getClassLoader().getParent();
        System. out.println(cl.getClass().getName());
          addSecrity(out, in);
    }

    public static void addSecrity(OutputStream dest, InputStream src)
              throws IOException {
          int b = 0;
          while ((b = src.read()) != -1) {
             b = b ^ 0xff;
             dest.write(b);
         }

    }

    @Override
    protected java.lang.Class<?> findClass(String name)
              throws ClassNotFoundException {
         String srcPath = "G:\\workplace\\javase\\lib\\" ;
         InputStream in = null;
          try {
             in = new FileInputStream(srcPath+name+".class" );
         } catch (FileNotFoundException e) {
             e.printStackTrace();
         }
         ByteArrayOutputStream baos = new ByteArrayOutputStream();
          try {
              addSecrity(baos,in);
         } catch (IOException e) {
             e.printStackTrace();
         }
          byte[] bytes = baos.toByteArray();
          Class clazz = defineClass (bytes, 0, bytes.length );
          return clazz;
    };

    private String name;

    public MyClassLoader() {
    }

    public MyClassLoader(String name) {
          this.name = name;
    }

}

有包名的类不能调用无包名的类