tomcat 容器是如何创建 servlet 类实例？用到了什么原理？

import javax.servlet.Servlet;
import java.lang.reflect.Constructor;

public class ServletInstanceCreator {
    public static Servlet createServletInstance(String servletClassName) throws Exception {
        // 加载 Servlet 类
        Class<?> servletClass = Class.forName(servletClassName);
        
        // 检查是否实现了 Servlet 接口
        if (!Servlet.class.isAssignableFrom(servletClass)) {
            throw new IllegalArgumentException("Class " + servletClassName + " does not implement Servlet interface");
        }
        
        // 获取构造函数并创建实例
        Constructor<?> constructor = servletClass.getConstructor();
        Servlet servletInstance = (Servlet) constructor.newInstance();
        
        return servletInstance;
    }

    public static void main(String[] args) {
        try {
            Servlet servlet = createServletInstance("com.example.MyServlet");
            // 初始化 Servlet 实例
            servlet.init(null);
            // 处理请求
            servlet.service(null, null);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}