package com.interview.javabasic.reflect;

public class Robot {
    private String name;
    public void sayHi(String helloSentence){
        System.out.println(helloSentence + " " + name);
    }
    private String throwHello(String tag){
        return "Hello " + tag;
    }
}

package com.interview.javabasic.reflect;

import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

public class ReflectSample {
    public static void main(String[] args) throws ClassNotFoundException, IllegalAccessException, InstantiationException, InvocationTargetException, NoSuchMethodException, NoSuchFieldException {
        Class rc = Class.forName("com.interview.javabasic.reflect.Robot");
        
        Robot r = (Robot) rc.newInstance();
        System.out.println("Class name is " + rc.getName());
        
        Method getHello = rc.getDeclaredMethod("throwHello", String.class);
        getHello.setAccessible(true); // 調用私有方法需要加，不然會報錯Exception in thread "main" java.lang.IllegalAccessException
        Object str = getHello.invoke(r, "Bob");
        System.out.println("getHello result is " + str);
        
        Method sayHi = rc.getMethod("sayHi", String.class);
        sayHi.invoke(r, "Welcome");
        
        Field name = rc.getDeclaredField("name");
        name.setAccessible(true);
        name.set(r, "Alice");
        sayHi.invoke(r, "Welcome");
    }
}

protected Class<?> findClass(String name) throws ClassNotFoundException {
        throw new ClassNotFoundException(name);
    }
    protected final Class<?> defineClass(byte[] b, int off, int len) throws ClassFormatError{
        return defineClass(null, b, off, len, null);
    }

    public class MyClassLoader extends ClassLoader{
    
        /** 路徑 */
        private String path;
    
        /** 名稱 */
        private String classLoaderName;
    
        /** 全參構造函數 */
        public MyClassLoader(String path, String classLoaderName) {
            this.path = path;
            this.classLoaderName = classLoaderName;
        }
    
        @Override
        public Class findClass(String name){
            byte[] b = loadClassData(name);

            return defineClass(name,b,0,b.length);
        }

        /** 用於載入類文件 */
        private byte[] loadClassData(String name) {
            /** 全路徑1 */
            name = path + name + ".class";
            /** jdk1.8新特性，不用手動關閉 */
            try(
                InputStream in = new FileInputStream(new File(name));
                ByteArrayOutputStream out = new ByteArrayOutputStream();) 
                {

                int i = 0;
                while ((i = in.read()) != -1){
    
                    out.write(i);
                }

                return out.toByteArray();
            } catch (IOException e) {
                e.printStackTrace();
                return null;
            }
        
        }
    }
    //檢測類
    public class ClassLoaderChecker{
		public static void main(String[] args){
		MyClassLoader m=new MyClassLoader(path:"Users/baidu/Desktop/"，classLoaderName:"myClassLoader");
		Class c=m.loadClass(name:"Wali");
		System.out.println(c.getClassLoader());//結果是MyClassLoader
		System.out.println(c.getClassLoader().getParent());//結果是AppClassLoader
		System.out.println(c.getClassLoader());//結果是ExtClassLoader
		System.out.println(c.getClassLoader());//結果是null
		c.newInstance();
	}