jar 包class动态加载问题 ，请高手指教 ！

Question

我已经实现jar包的动态加载，但加载未知的第三方jar包不能清楚，第三方包中哪个是子类，哪个是父类，这样在动态加载时 ，如果先加载子类会报找不到父类异常，请高手指教，您是如何解决这个问题地 *^_^*

Answer 1

我书写的实现类如下：
package com.sunrising.common.classloader;
import java.io.BufferedInputStream;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;
import java.util.Enumeration;
import java.util.Hashtable;
import java.util.zip.ZipEntry;
import java.util.zip.ZipInputStream;
public class MyClassLoader extends ClassLoader {
    Hashtable loadedClasses;
    public MyClassLoader() {
        loadedClasses = new Hashtable();
        readJarFile("");
        createJarClass("");
    }
    private  Hashtable readJarFile(String jarName){
        ZipInputStream zistream;
        File file = new File("lib"+File.separator+"g.jar");
        URL url = null;
        try {
            url = file.toURL();
        } catch (MalformedURLException ex) {
            ex.printStackTrace();
        }
        try
        {
            zistream = new ZipInputStream(url.openStream());
        }
        catch(IOException e)
        {
              return null;
        }
        try
        {
            ZipEntry classEntry;
            while((classEntry = zistream.getNextEntry()) != null)
            {
                String className = classEntry.getName().replaceAll("/", ".");
                if(className.endsWith(".class"))
                {
                    byte data[] = readClassBytesFromInputStream(zistream);
                    if(data != null)
                    {
                        loadedClasses.put(className, data);
                    }
                }
                zistream.closeEntry();
            }
            zistream.close();
        }
        catch(IOException e)
        {
            return null;
        }
        return loadedClasses;
    }
    public synchronized void createJarClass(String className){
        Hashtable loadedClasses   =   this.loadedClasses;
        Enumeration  enum = null;
        Class newClass = null;
        String   name = null;
        enum=loadedClasses.keys();
        byte []classData =new byte[0];
        if(!className.trim().equals("")){
            className = className+".class";
            classData = classData=(byte[])loadedClasses.get(className);
            newClass = defineClass(null, classData, 0, classData.length);
            loadedClasses.put(className,newClass);
        }
        while(enum.hasMoreElements())
        { 
            name=(String)enum.nextElement();  
            try{
                classData=(byte[])loadedClasses.get(name);
                newClass = defineClass(null, classData, 0, classData.length);
                loadedClasses.put(name,newClass);
            }catch(Exception ex){
                System.out.println(name+" has been create class");
            }
           
        }
    }
    protected byte[] readClassBytesFromInputStream(InputStream istream)
    {
        ByteArrayOutputStream baostream = new ByteArrayOutputStream();
        BufferedInputStream bistream = new BufferedInputStream(istream);
        try
        {
            byte buffer[] = new byte[1024];
            int bytesRead;
            while((bytesRead = bistream.read(buffer, 0, 1024)) != -1) 
                baostream.write(buffer, 0, bytesRead);
            buffer = null;
        }
        catch(IOException e)
        {
            return null;
        }
        return baostream.toByteArray();
    }    public synchronized Class loadClass(String className, boolean resolve)
            throws ClassNotFoundException {
        Class newClass = null;
        byte[] classData = null;
        newClass = (Class) loadedClasses.get(className);
           if (newClass != null) {
            if (resolve)
                resolveClass(newClass);
            return newClass;
        }
        try {
            newClass = findSystemClass(className);
            return newClass;
        } catch (ClassNotFoundException e) {
            System.out.println(className + " is not a system class!");
        }
       try {       classData = this.getLocalClassData(className);
            newClass = defineClass(null, classData, 0, classData.length);
            if (newClass == null)
                throw new ClassNotFoundException(className);
    } catch (Exception e) {
            this.createJarClass(className);    
        }
        loadedClasses.put(className, newClass);
            if (resolve) {
            resolveClass(newClass);
        }
        return newClass;
    }
     protected byte[] getClassData(String className) throws IOException {
        byte[] data;
        int length;
        try {
            URL url = new URL(className.endsWith(".class") ? className
                    : className + ".class");
            URLConnection connection = url.openConnection();
            InputStream inputStream = connection.getInputStream();
            length = connection.getContentLength();
            data = new byte[length];
            inputStream.read(data);
            inputStream.close();
            return data;
        } catch (Exception e) {
            throw new IOException(className);
        }
    }
    protected byte[] getLocalClassData(String className)throws IOException {
        byte[] data;
        int length;
        try {
            File file = new File("lib"+File.separator+className);
            URL url = file.toURL();
            URLConnection connection = url.openConnection();
            InputStream inputStream = connection.getInputStream();
            length = connection.getContentLength();
            data = new byte[length];
            inputStream.read(data);
            inputStream.close();
            return data;        } catch (Exception e) {
            throw new IOException(className);
        }
    }}

Answer 2

心得就是重写ClassLoader，入口直接走该类构造函数即可，里面运行的方法中的  jar 包名和
要加载的类名暂时是写死的