一般情况下，使用Spring、SpringMvc这些框架后，基本告别了Servlet、Filter、Listener。
但是在整合第三方框架时，可能还是会使用到Servlet，比如整合某报表插件时需要使用Servlet。
SpringBoot对整合这些基本的Web组件也提供了很好的支持。

1.整合Servlet

@WebServlet("/my")
public class MyServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
       this.doPost(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("name: "+req.getParameter("name"));
    }
}

2.整合Filter

@WebFilter("/*")
public class MyFilter implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        System.out.println("myfilter init");
    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        System.out.println("myfilter dofilter");
        filterChain.doFilter(servletRequest, servletResponse);      //放行
    }

    @Override
    public void destroy() {
        System.out.println("myfilter destory");
    }
}

3.整合Listener

//这里使用的是ServletRequestListener。
//对于HttpSessionListener和ServletContextListener等也是支持的。
@WebListener
public class MyListener implements ServletRequestListener {

    @Override
    public void requestDestroyed(ServletRequestEvent sre) {
        System.out.println("servletRequestListener requestDestroyed");
    }

    @Override
    public void requestInitialized(ServletRequestEvent sre) {
        System.out.println("servletRequestListener requestInitialized");
    }
}

4.启动类开启Servlet组件扫描，让Web组件生效

@SpringBootApplication
@ServletComponentScan
public class RunnerApplication {

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

}

5.测试

请求：http://localhost:8080/my?name=zhangsan

servlet.png