18. Spring Boot 、注册Servlet三大组件Servlet、Filter、Listener

由于SpringBoot默认是以jar包的方式启动嵌入式的Servlet容器来启动SpringBoot的web应用，没有web.xml文件

public class MyServlet extends HttpServlet {
    
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException ,IOException {
          resp.getWriter().println("<h1>hello world</h1>");
    };
    
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doPost(req, resp);
    }
}

public class MyFilter implements Filter{

    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
            throws IOException, ServletException {
        System.out.println("================Hello world Filter");
        chain.doFilter(request, response);
        
    }
}

public class MyListener implements ServletContextListener {
    @Override
    public void contextInitialized(ServletContextEvent sce) {
        ServletContextListener.super.contextInitialized(sce);
        System.out.println("-------------MyListener inited !");
    }
    
    
    @Override
    public void contextDestroyed(ServletContextEvent sce) {
        ServletContextListener.super.contextDestroyed(sce);
        System.out.println("----------------MyListener Destroy !");
    }
    
}

@Configuration
public class MyMvcConfig implements WebMvcConfigurer {
    //注册Servlet
    @Bean
    public ServletRegistrationBean<Servlet> myServlet(){
        return new ServletRegistrationBean<>(new MyServlet(),"/myServlet");
    }
    
    //注册Filter
    @Bean
    public FilterRegistrationBean<Filter> myFilter(){
        FilterRegistrationBean<Filter> filter = new FilterRegistrationBean<>();
        filter.setFilter(new MyFilter());
        filter.addUrlPatterns("/myServlet");
        
        FilterRegistrationBean<Filter> filter2 = new FilterRegistrationBean<>(new MyFilter(), myServlet());
        return filter2;
    }

    //注册Listener
    @Bean
    public ServletListenerRegistrationBean<EventListener> myListener(){
        ServletListenerRegistrationBean<EventListener> listener = new ServletListenerRegistrationBean<EventListener>(new MyListener());
        return listener;
    }

}