Java中反射的"暴破"机制(SetAccessible方法)详解

package com.java.SetAcc;

import java.lang.reflect.Constructor;

public class ReflectCon {
   public static void main(String[] args) throws Exception {

       Class cls = Class.forName("com.java.SetAcc.Student");
       //无参构造器创建实例
       Object o2 = cls.newInstance();
       System.out.println(o2);
       //访问公有带参构造器
       Constructor constructor = cls.getConstructor(String.class);
       Object o = constructor.newInstance("AAA");
       System.out.println(o);
       //访问私有的有参构造器
       Constructor constructor1 = cls.getDeclaredConstructor(String.class,int.class);
       //暴破！！！！
       constructor1.setAccessible(true);
       Object o1 = constructor1.newInstance("bbb",12);
       System.out.println(o1);



   }
}

class Student{
   public String name = "aaa";
   public int age = 10;

   //无参构造
   public Student() {
   }

   public Student(String name){
       this.name = name;
   }

   private Student(String name, int age) {
       this.name = name;
       this.age = age;
   }

   @Override
   public String toString() {
       return "Student{" +
               "name='" + name + '\'' +
               ", age=" + age +
               '}';
   }
}

package com.java.SetAcc;

import java.lang.reflect.Field;

public class ReflectField_ {
    public static void main(String[] args) throws Exception {

        Class<?> cls = Class.forName("com.java.SetAcc.User");
        //1. 访问无参 必须带无参构造器
        Object o = cls.newInstance();
        //访问public的属性
        Field name = cls.getField("name");
        //可以通过set修改值
        name.set(o,"bbb");
        System.out.println(name.get(o));

        //2.访问私有属性
        Field age = cls.getDeclaredField("age");
        //暴破！！！ 直接访问
        age.setAccessible(true);
        age.set(o,12);
        System.out.println(o);

        //访问静态
        Field salary = cls.getField("salary");
        //可以通过null修改属性值
        salary.set(null,2000);
        System.out.println(salary.get(null));



    }
}
class User{
    public String name = "aaa";
    private int age = 10;
    public static double salary = 10000;

    public User() {
    }

    public User(String name, int age) {
        this.name = name;
        this.age = age;
    }

    @Override
    public String toString() {
        return "User{" +
                "name='" + name + '\'' +
                ", age=" + age +
                '}';
    }
}

package com.java.SetAcc;

import java.lang.reflect.Method;

public class ReflectMethod_ {
    public static void main(String[] args) throws Exception {
        Class<?> cls = Class.forName("com.java.SetAcc.Person");

        Object o = cls.newInstance();
        //公有方法
        Method hi = cls.getMethod("hi", String.class);
        //调用的时候一定带上属性
        hi.invoke(o,"aaa");

        //私有方法
        Method hello = cls.getDeclaredMethod("hello", int.class);
        hello.setAccessible(true);
        hello.invoke(o,10);

        //静态ff
        Method bye = cls.getDeclaredMethod("bye");
        bye.setAccessible(true);
        bye.invoke(null);




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

    public Person() {
    }

    public Person(String name, int age) {
        this.name = name;
        this.age = age;
    }

    public void hi(String name){
        System.out.println("hi方法"+name);
    }

    private void hello(int age){
        System.out.println("hello方法"+age);
    }

    static void bye(){
        System.out.println("bye方法");
    }

    @Override
    public String toString() {
        return "Person{" +
                "name='" + name + '\'' +
                ", age=" + age +
                '}';
    }
}