不同类装载器生成的Class对象，所生成的实例相互转化报ClassCastException

package com.jaychang.demo;

public class Dog {
	public String say(String name) {
		System.out.println("Hello " + name);
		return "Hello " + name;
	}
}

 

package com.jaychang.demo;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;

public class ClassLoaderTest {
	static class MyClassLoader extends ClassLoader {
		public Class<?> getClass(byte[] byteArray, int off, int len) {
			return super.defineClass(byteArray, off, len);
		}
	}

	public static void main(String[] args) {
		MyClassLoader myClassLoader = new MyClassLoader();
		File classFile = new File(
				"F:/Workspace/classloader-demo/target/classes/com/jaychang/demo/Dog.class");
		ByteArrayOutputStream baos = null;
		BufferedOutputStream bos = null;
		FileInputStream fis = null;
		BufferedInputStream bis = null;
		try {
			fis = new FileInputStream(classFile);
			baos = new ByteArrayOutputStream();
			bis = new BufferedInputStream(fis);
			bos = new BufferedOutputStream(baos);
			byte[] buff = new byte[1024];
			int len = -1;
			while ((len = bis.read(buff, 0, 1024)) != -1) {
				bos.write(buff, 0, len);
			}
			bos.flush();
			byte[] byteArray = baos.toByteArray();
			Class clazz1 = myClassLoader.getClass(byteArray, 0,
					byteArray.length);
			Class clazz2 = Class.forName("com.haipicheng.dubbo_demo.Dog");
			Class clazz3 = Dog.class;
			System.out.println("clazz1类装载器为" + clazz1.getClassLoader()
					+ ",clazz2类装载器为" + clazz2.getClassLoader() + ",clazz3类装载器为"
					+ clazz3.getClassLoader());
			System.out.println("clazz1 == clazz2 ?" + (clazz1 == clazz2));
			System.out.println("clazz2 == clazz3 ?" + (clazz2 == clazz3));
			System.out.println("clazz1 == clazz3 ?" + (clazz1 == clazz3));

		} catch (FileNotFoundException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		} catch (SecurityException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IllegalArgumentException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (ClassNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} finally {
			if (null != fis) {
				try {
					fis.close();
				} catch (IOException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
			}
			if (null != bis) {
				try {
					bis.close();
				} catch (IOException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
			}
			if (null != baos) {
				try {
					baos.close();
				} catch (IOException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
			}
			if (null != bos) {
				try {
					bos.close();
				} catch (IOException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
			}
		}
	}
} 

com.jaychang.demo.Dog,com.jaychang.demo.Dog,com.jaychang.demo.Dog

clazz1类装载器为com.jaychang.demo.ClassLoaderTest$MyClassLoader@97d01f,clazz2类装载器为sun.misc.Launcher$AppClassLoader@472d48,clazz3类装载器为sun.misc.Launcher$AppClassLoader@472d48

clazz1 == clazz2 ?false

clazz2 == clazz3 ?true

clazz1 == clazz3 ?false

 

说明不同类装载器加载生成的Class对象，尽管调用getName得到的全限定名称是一一样的，但是他们是不同类装载器装载的，由Class对象生成对应的实例就不能相互转换，就会报ClassCastException了