java 反射给对象新增属性并赋值工具类

以下是示例代码，可以通过反射给对象新增属性并赋值：

import java.lang.reflect.Field;

public class ReflectUtil {
    public static void setFieldValue(Object obj, String fieldName, Object fieldValue) throws Exception {
        Class<?> clazz = obj.getClass();
        Field field = clazz.getDeclaredField(fieldName);
        field.setAccessible(true);
        field.set(obj, fieldValue);
    }
}

使用示例：

public class User {
    private String name;
    private int age;
  
    // getter and setter
}

public class Main {
    public static void main(String[] args) throws Exception {
        User user = new User();
        ReflectUtil.setFieldValue(user, "name", "Tom");
        ReflectUtil.setFieldValue(user, "age", 18);
        System.out.println(user.getName()); // Tom
        System.out.println(user.getAge()); // 18
    }
}