定义父类

@Data
public class Person {

    /**
     * 姓名
     */
    private String name;
}

定义子类

@Data
@ToString(callSuper = true)
public class Student extends Person {

    /**
     * 学号
     */
    private String studentCode;

}

利用反射给父类属性赋值

public class ReflexTest {

    @Test
    void test() throws ClassNotFoundException, NoSuchFieldException, IllegalAccessException, NoSuchMethodException, InvocationTargetException, InstantiationException {

        Class<?> stuClass  = Class.forName("com.ijunfu.domain.Student");
        Student student = (Student) stuClass.getDeclaredConstructor().newInstance();

        Class<?> superclass = stuClass.getSuperclass();

        Field nameField = superclass.getDeclaredField("name");
        nameField.setAccessible(Boolean.TRUE);
        nameField.set(student, "ijunfu");

        System.out.println(student);
    }
}

扩展：使用切面拦截所有Get请求，并给请求中参数的父类赋值

定义切面：

@Aspect
@Component
public class GetRequestAspect {

    @Pointcut("@annotation(org.springframework.web.bind.annotation.GetMapping)")
    public void pointcut() {

    }

    @Around("pointcut()")
    public Object around(ProceedingJoinPoint joinPoint) throws Throwable {

        Object[] args = joinPoint.getArgs();

       if(Objects.nonNull(args) && args.length>0 && args[0] instanceof Person) {

            Field nameField = Person.class.getDeclaredField("name");
            nameField.setAccessible(Boolean.TRUE);
            nameField.set(args[0], "ijunfu");
        }

        return joinPoint.proceed();

    }
}

定义Controller：

@Slf4j
@RestController
@RequestMapping("/student")
public class StudentController {

    @GetMapping
    public String query(Student student) {
        log.warn("{}", student);
        return "OK";
    }
}

延伸思考：可以设置一些全局性的属性，比如角色是否为admin等