Java 注解与反射（四）反射的使用

Java 注解与反射（四）反射的使用

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

public class Test02 {
    public static void main(String[] args) throws ClassNotFoundException, IllegalAccessException, InstantiationException, NoSuchMethodException, InvocationTargetException, NoSuchFieldException {
        Class c1 = Class.forName("com.zzz.reflection.User");

        User user = (User) c1.newInstance();    //直接调用为调用的无参构造，若实体类里无无参构造，则报错
        System.out.println(user);

        Constructor declaredConstructor = c1.getDeclaredConstructor(String.class, int.class, int.class);    //获取有参构造器
        User user2 = (User) declaredConstructor.newInstance("zzz2", 10, 123);    //使用有参构造器实例化一个对象
        System.out.println(user2);

        User user3 = (User) c1.newInstance();   //通过反射调用一个普通方法
        Method setName = c1.getDeclaredMethod("setName", String.class);
        setName.invoke(user3,"zzz3");     //激活方法，如果方法为private则需在invoke前setAccessible(true)
        System.out.println(user3.getName());

        User user4 = (User) c1.newInstance();   //通过反射操作一个属性
        Field name = c1.getDeclaredField("name");
        name.setAccessible(true);       //不能直接操作私有属性，需关闭安全检测\给与操作权限
        name.set(user4,"zzz4");
        System.out.println(user4.getName());


    }
}