Java反射使用实例

一、准备测试类如下：

package com.fh;

public class Player {
    private String name;
    private Integer age;

    public String country;

    public Player() {
    }

    public Player(String name, Integer age, String country) {
        this.name = name;
        this.age = age;
        this.country = country;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public String getCountry() {
        return country;
    }

    public void setCountry(String country) {
        this.country = country;
    }

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

    public String getFlyInfo(String gameName, Integer distance) {
        return "In "+ gameName+", my name is " + name + ", I am " + age + " years old, I come from "+country+", I can fly " + distance + " meter!";
    }

    private String bye(String gameName) {
        return "bye, "+gameName;
    }
}

二、使用实例：

package com.fh;

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

public class TestDemo1 {
    public static void main(String[] args) {
        Player p1 = new Player("ZhangSan", 18 , "China");
        p1.getFlyInfo("DOTA2", 3);

        try {
            //获取类对象的三种方式：
            Class<Player> playerClassObj1 = Player.class; // 根据类获取类对象
            Class<? extends Player> playerClassObj2 = p1.getClass(); // 根据类的实例对象获取类对象
            Class<?> playerClassObj3 = Class.forName("com.fh.Player"); //  根据包路径下的类名获取类对象

            System.out.println(playerClassObj1.getName()); // 获取带包名的类名
            System.out.println(playerClassObj1.getSimpleName());// 获取单纯的类名
            System.out.println(playerClassObj1.getSuperclass());// 获取父类
            System.out.println(playerClassObj1.getPackage());// 获取包名

            //获取构造方法
            Constructor<?>[] playerClassConObjs = playerClassObj1.getDeclaredConstructors(); // 获取所有构造方法对象（包括私有）
            for (Constructor<?> playerClassConObj : playerClassConObjs) {//  遍历所有构造方法对象
                System.out.println(playerClassConObj);//  打印构造方法对象
            }
            Constructor<Player> playerClassNoArgsConObj = playerClassObj1.getConstructor();//获取空参构造方法对象
            Constructor<Player> playerClassAllArgsConObj = playerClassObj1.getConstructor(String.class, Integer.class, String.class);// 获取有参构造方法对象
            Player p2 = playerClassAllArgsConObj.newInstance("Yuki", 17, "Japan");// 利用有参构造方法对象，创建对象p2
            System.out.println(p2);
            //获取&修改公开字段：
            Field countryFieldObj = playerClassObj1.getField("country");// 获取公开字段对象：country
            String countryVal = (String) countryFieldObj.get(p1);//  获取对象p1的country字段的属性值
            countryFieldObj.set(p1,"USA");// 在country字段，对对象p1设置（修改）属性值
            //获取&修改所有字段（包括私有）：
            Field nameFieldObj = playerClassObj1.getDeclaredField("name");// 获取私有字段对象：name
            nameFieldObj.setAccessible(true);//  设置私有字段，要先设置可访问
            String nameVal = (String) nameFieldObj.get(p1);// 获取对象p1的name字段的属性值
            nameFieldObj.set(p1,"Jack");// 在name字段，对对象p1设置（修改）属性值

            //获取&修改公开方法
            Method flyMethodObj = playerClassObj1.getMethod("getFlyInfo", String.class, Integer.class);//获取公开方法对象：getFlyInfo
            String flyMethodResult = (String)flyMethodObj.invoke(p1, "WangZheRongYao", 36);// 调用对象p1的getFlyInfo方法，并传入参数，获取返回值
            System.out.println(flyMethodResult);// 打印返回值
            //获取&修改所有方法（包括私有）
            Method byeMethodObj = playerClassObj1.getDeclaredMethod("bye", String.class);// 获取私有方法对象：bye
            byeMethodObj.setAccessible(true);// 设置私有方法，要先设置可访问
            String byeMethodResult = (String)byeMethodObj.invoke(p1, "Genshin");//  调用对象p1的bye方法，并传入参数，获取返回值
            System.out.println(byeMethodResult);//  打印返回值
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }
}