SpringBoot中Web原生组件注入(Servlet、Filter、Listener)

一、使用Servlet API

1. 在主类中添加@ServletComponentScan(basePackages = "cn.edu.tiangong")注解。

   1. 作用：制定原生servlet组件都放在哪里

   2. 代码：

      @ServletComponentScan(basePackages = "cn.edu.tiangong")
      @SpringBootApplication
      public class SpringBootDemo05WebApplication {
      
          public static void main(String[] args) {
              SpringApplication.run(SpringBootDemo05WebApplication.class, args);
          }
      
      }
      

2. 编写一个servlet实现HttpServlet，并添加注解@WebServlet(urlPatterns = "/my")

   1. 效果：直接响应，没有经过SpringBoot的拦截器

   2. 代码：

      @WebServlet(urlPatterns = "/my")
      public class MyServlet extends HttpServlet {
      
          @Override
          protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
              resp.getWriter().write("6666");
          }
      }
      

3. 编写一个filter实现Filter接口，并且添加@WebFilter(urlPatterns = {"/css/*","/image/*"})注解

   1. 效果：对根目录下css和image路径下的所有访问请求进行过滤操作

   2. 代码：

      @Log4j2
      @WebFilter(urlPatterns = {"/css/*","/image/*"})
      // /*是servlet的写法
      // /**是Spring的写法
      public class MyFilter implements Filter {
      
          @Override
          public void init(FilterConfig filterConfig) throws ServletException {
              log.info("MyFilter初始化了");
          }
      
          @Override
          public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
              log.info("MyFilter工作");
              filterChain.doFilter(servletRequest, servletResponse);
          }
      
          @Override
          public void destroy() {
              log.info("MyFilter销毁了");
          }
      }
      

二、使用RegistrationBean

• ServletRegistrationBean
• FilterRegistrationBean
• ServletListenerRegistrationBean

2.1 ServletRegistrationBean

1. 先写一个Servlet，这个servlet不用添加@WebServlet注解

   public class MyServlet extends HttpServlet {
   
       @Override
       protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
           resp.getWriter().write("6666");
       }
   }
   

2. 再写一个MyRegistrationConfig，添加@Configuration注解

   /**
    * 【注意事项】
    * 1. 没有添加(proxyBeanMethods = false)，这样可以保证依赖的组件始终是单实例的，防止容器中组件冗余
    * 2. 为什么自己写的myServlet是直接响应的没有经过SpringBoot的拦截器？？？
    */
   //@Configuration(proxyBeanMethods = false)
   @Configuration(proxyBeanMethods = true)
   public class MyRegistrationConfig {
   
       @Bean
       public ServletRegistrationBean myServlet() {
           MyServlet servlet = new MyServlet();
           return new ServletRegistrationBean(servlet, "/my", "/your");
       }
   
       @Bean
       public FilterRegistrationBean myFilter() {
           MyFilter filter = new MyFilter();
           // 1. 只拦截myServlet的路径
   //        return new FilterRegistrationBean(filter, myServlet());
           // 2. 拦截自定义路径
           FilterRegistrationBean filterRegistrationBean = new FilterRegistrationBean(filter);
           filterRegistrationBean.setUrlPatterns(Arrays.asList("/my", "/css/*"));
           return filterRegistrationBean;
       }
   }