package com.yang.myclass.hotswap;

import java.io.File;
import java.io.IOException;
import java.io.InputStream;

public class MyClassLoader3 extends ClassLoader {

/**
 * 自定义类加载器
 * @param name
 * @return
 * @throws ClassNotFoundException
 */
@Override
protected Class<?> findClass(String name) throws ClassNotFoundException {

    byte[] classByte = getClassData(name);
    if(classByte==null){
        throw new ClassNotFoundException();
    }else{
        //生成class
        return defineClass(name,classByte,0,classByte.length);
    }


}

private byte[] getClassData(String className){
    //读取类文件的路径
    String classPath = "/" + className.replace(".", "/")+".class";
    InputStream is = this.getClass().getResourceAsStream(classPath);
    byte [] classBytes = null;
    try {
        classBytes = new byte[is.available()];
        is.read(classBytes);
    } catch (IOException e) {
        e.printStackTrace();
    }
    return classBytes;
}

}

 以上是自定义类的加载器
 

package com.yang.myclass.hotswap.impl;

import com.yang.myclass.hotswap.inter.ParentCalss;

public class ChildrenClass implements ParentCalss {

private String name;
public ChildrenClass(String name){
    this.name = name;
}
public ChildrenClass(){

}
@Override
public void print() {
    System.out.println("我是孩子1");
}

@Override
public String toString() {
    return name+"1";
}

}
以上是自定义类

 以下是测试类

package com.yang.myclass.hotswap;

import com.yang.myclass.hotswap.impl.ChildrenClass;
import com.yang.myclass.hotswap.inter.ParentCalss;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.logging.Logger;

public class MyHotSwapTest {

public static  Logger logger = Logger.getLogger(String.valueOf(MyHotSwapTest.class));

public static void main(String[] args) throws ClassNotFoundException {
    String name = "com.yang.myclass.hotswap.impl.ChildrenClass";
    while (true){
        try {
            Thread.sleep(2000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

_ MyClassLoader3 myClassLoader3 = new MyClassLoader3();
_ Class class3 = myClassLoader3.findClass(name);
ParentCalss childrenClass = new ChildrenClass();
System.out.println(childrenClass.toString());

    }

}

}

 测试类中创建对象，如果用new的话，会发现：输出的信息还是修改前的信息，而不是修改后的信息；但是如果通过class反射调用，则是最新的信息。
 不过我们一般代码中都是使用new来直接创建对象，name这样的热部署意义何在？