Spring MVC的核心控制器DispatcherServlet会处理所有的请求，项目中使用Controller基本能解决大部分的功能需求，但有时也需要使用Servlet，比如实现拦截和监听功能；

Servlet 是 Sun 公司所设计开发的可以用于接收和处理 HTTP 请求的 Java 类，Spring MVC 这样的框架就是对 Servlet 的二次封装

即servlet和controller一样能接收请求

使用servlet的两种方式

方式一

使用@WebServlet和@ServletComponentScan注解

@WebServlet(urlPatterns="/ServletDemo/*")
public class MyServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("doGet");
        resp.getWriter().print("Get Servlet ServletDemo");
    }


    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("doPost");
        resp.getWriter().print("Post Servlet ServletDemo");
    }

    @Override
    protected void doPut(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("doPut");
        resp.getWriter().print("Put Servlet ServletDemo");
    }


    @Override
    protected void doDelete(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("doDelete");
        resp.getWriter().print("Delete Servlet ServletDemo");
    }
}

@SpringBootApplication
@ServletComponentScan
public class ServletApplication {

    public static void main(String[] args) {
        SpringApplication.run(ServletApplication.class, args);
    }

}

方式二

使用配置类

@Configuration
public class ServletConfig {

    @Bean
    public ServletRegistrationBean myServletRegistrationBean() {
        ServletRegistrationBean servletRegistrationBean=new ServletRegistrationBean(
                new MyServlet(),"/ServletDemo"
        );
        return servletRegistrationBean;
    }

}

参考文章

【1】SpringBoot中使用Servlet的两种方式