Java反射机制概述

package com.atguigu.java;
import org.junit.Test;
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
/**
 * @author Dxkstart
 * @create 2021-11-23-18:15
 */
public class ReflectionTest {
    //反射之后
    @Test
    public void test1() throws Exception {
        Class<Person> clazz = Person.class;
        //1.通过反射，创建Person类的对象
        Constructor<Person> constructor = clazz.getConstructor(String.class, int.class);
        Person tom = constructor.newInstance("Tom", 12);
        System.out.println(tom.toString());
        //2.通过反射，调用对象指定的属性、方法
        //调用属性
        Field age = clazz.getDeclaredField("age");
        age.set(tom,10);
        System.out.println(tom.toString());
        //调用方法
        Method show = clazz.getDeclaredMethod("show");
        show.invoke(tom);
        System.out.println("************************");
        //通过反射，可以调用Person类额私有结构的，比如：私有构造器，方法，属性
        //私有构造器
        Constructor<Person> con1 = clazz.getDeclaredConstructor(String.class);
        con1.setAccessible(true);
        Person jerry = con1.newInstance("Jerry");
        System.out.println(jerry);
        //私有属性
        Field name = clazz.getDeclaredField("name");
        name.setAccessible(true);
        name.set(jerry,"Mack");
        System.out.println(jerry);
        //私有方法
        Method showNation = clazz.getDeclaredMethod("showNation", String.class);
        showNation.setAccessible(true);
        String nation = (String) showNation.invoke(jerry,"china");
        System.out.println(nation);
    }
}