文章标题

反射

package org.test.base;

public class User {

    private String name;
    private Integer sex;

    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Integer getSex() {
        return sex;
    }
    public void setSex(Integer sex) {
        this.sex = sex;
    }
    @Override
    public String toString() {
        return "User [name=" + name + ", sex=" + sex + "]";
    }

}

package org.test.base;
import java.lang.reflect.Field;

public class Hi {
    public static void main(String[] args) throws IllegalArgumentException, IllegalAccessException, InstantiationException, ClassNotFoundException {

        System.out.println(1);

        User he = new User();//有实例对象的反射
        Field[] fields_he = he.getClass().getDeclaredFields();
        he.setName("zhang san");
        for(Field field : fields_he){
            field.setAccessible(true);//暴力反射，将private强制转换为public
            System.out.println(field.getName()+" ："+field.get(he));
        }

        System.out.println(2);

        User you = null;//无实例对象的反射
        you = (User) Class.forName(User.class.getName()).newInstance();
        you.setName("li si");
        Field[] fields_you = you.getClass().getDeclaredFields();
        for(Field field : fields_you){
            field.setAccessible(true);
            System.out.println(field.getName()+" ："+field.get(you));
        }

        System.out.println(3);

        User she = null;//无实例对象的反射
        she = (User) ClassLoader.getSystemClassLoader().loadClass(User.class.getName()).newInstance();
        she.setName("wang wu");
        Field[] fields_she = she.getClass().getDeclaredFields();
        for(Field field : fields_she){
            field.setAccessible(true);
            System.out.println(field.getName()+" ："+field.get(she));
        }   

    }
}

输出结果：
1
name ：zhang san
sex ：null
2
name ：li si
sex ：null
3
name ：wang wu
sex ：null