反射概念

package com.oracle.demo01;

public class Person {
	private String name;
	public int age;

	public Person() {
		System.out.println("public Person()");
	}

	public Person(String name) {
		this.name = name;
		System.out.println(" public Person(String name)");
	}

	private Person(int age) {
		this.age = age;
		System.out.println("private Person(int age)");
	}

	static {
		System.out.println("静态代码块");
	}
	public void eat() {
		System.out.println("public void eat()");
	}
	public void sleep(String name,int age) {
		System.out.println(name+"......"+age);
		System.out.println("public void sleep(String name,int age)");
	}
	public void sleep(String name) {
		System.out.println("public void sleep(String name)");
	}
	private void smoke(int age){
		System.out.println("private void smoke(int age)");
	}

	public String toString() {
		return "Person [name=" + name + ", age=" + age + "]";
	}
	
}

package com.oracle.demo01;

public class Demo02 {
	   public static void main(String[] args) throws ClassNotFoundException {
	   //获取字节码文件对象
	   //1.通过对象获取
		 Class c1=new Person().getClass();
		 System.out.println(c1);
	   //2.通过类名获取
		 Class  c2=Person.class;
		 System.out.println(c2);
		 //System.out.println(c1==c2);//true 比的地址 只有一个所以是true
	   //3.通过Class类的静态方法获取
		 Class c3=Class.forName("com.oracle.demo01.Person");
		 System.out.println(c3);
	}
}

package com.oracle.demo02;

import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;

import com.oracle.demo01.Person;

public class Demo01 {
	public static void main(String[] args) throws ClassNotFoundException, NoSuchMethodException, SecurityException, InstantiationException, IllegalAccessException, IllegalArgumentException, InvocationTargetException {
		//method02();
		//method03();
		method04();
	}

	public static void method01() throws ClassNotFoundException {
		// 获取字节码文件对象
		Class c = Class.forName("com.oracle.demo01.Person");
		// 获取所有公共的构造方法对象数组
		// Constructor[] cons=c.getConstructors();
		// 获取所有的构造方法
		Constructor[] cons = c.getDeclaredConstructors();
		for (Constructor con : cons) {
			System.out.println(con);
		}
	}

	public static void method02() throws ClassNotFoundException, NoSuchMethodException, SecurityException, InstantiationException, IllegalAccessException, IllegalArgumentException, InvocationTargetException {
        //获取字节码文件对象
		Class c=Class.forName("com.oracle.demo01.Person");
		//获取空参构造方法对象
		Constructor con=c.getConstructor();
		//调用构造方法创建对象
		Object obj=con.newInstance();
		//向下转型
		Person p=(Person)obj;
		p.eat();
	}
	public static void method03() throws ClassNotFoundException, NoSuchMethodException, SecurityException, InstantiationException, IllegalAccessException, IllegalArgumentException, InvocationTargetException {
        //获取字节码文件对象
		Class c=Class.forName("com.oracle.demo01.Person");
		//获取有参构造方法对象
		Constructor con=c.getConstructor(String.class);
		//调用构造方法创建对象
		Object obj=con.newInstance("张三丰");
		//向下转型
		Person p=(Person)obj;
		p.eat();
	}
	//暴力反射:抢银行(违反了面向对象的封装思想，破坏了程序 的安全性，不推荐使用!)
	public static void method04() throws ClassNotFoundException, NoSuchMethodException, SecurityException, InstantiationException, IllegalAccessException, IllegalArgumentException, InvocationTargetException {
        //获取字节码文件对象
		Class c=Class.forName("com.oracle.demo01.Person");
		//获取有参构造方法对象
		Constructor con=c.getDeclaredConstructor(int.class);
		//暴力反射，取消java语言检测访问
		con.setAccessible(true);
		//调用构造方法创建对象
		Object obj=con.newInstance(666);
		//向下转型
		Person p=(Person)obj;
		p.eat();
	}
}

package com.oracle.demo02;

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

import javax.print.attribute.standard.Media;

public class Demo03 {
	 public static void main(String[] args) throws ClassNotFoundException, NoSuchMethodException, SecurityException, InstantiationException, IllegalAccessException, IllegalArgumentException, InvocationTargetException {
		//获取字节码文件对象
		 Class c=Class.forName("com.oracle.demo01.Person");
	    //获取公共有参成员方法
		 Method method=c.getMethod("sleep",String.class,int.class);
		//快速创建对象
		 Object obj=c.newInstance();
		 //调用方法
		  method.invoke(obj,"张三丰",666);
	}
}