過濾器，監聽器，轉發器

1、customFilter過濾器

public class CustomFilter implements Filter {

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        System.out.println("init filter");
    }

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

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

}

2、CustomListener監聽器

public class CustomListener implements ServletContextListener
 
 {

    @Override
    public void contextInitialized(ServletContextEvent sce) {
        System.out.println("contextInitialized");
    }

    @Override
    public void contextDestroyed(ServletContextEvent sce) {
        System.out.println("contextDestroyed");
    }

3、轉發器CustomServlet

public class
 
 CustomServlet extends HttpServlet{
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("servlet get method");
        doPost(req,resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("servlet post method");
        resp.getWriter().write("hello world");
    }
}

方法一：通過註冊ServletRegistrationBean，FilterRegistrationBean，ServletListenerRegistrationBean獲得控制

@SpringBootApplication
public class SpringBootDemo71Application {
    @Bean//註冊Servlet
    public ServletRegistrationBean servletRegistrationBean() {
        return new ServletRegistrationBean(new CustomServlet(), "/roncoo");
    }
    @Bean//註冊Filter
    public FilterRegistrationBean filterRegistrationBean() {
        return new FilterRegistrationBean(new CustomFilter());
    }
    @Bean//註冊Listener
    public ServletListenerRegistrationBean<CustomListener> servletListenerRegistrationBean() {
        return new ServletListenerRegistrationBean<CustomListener>(new CustomListener());
    }
    public static void main(String[] args) {
        SpringApplication.run(SpringBootDemo71Application.class, args);
    }
}

方法二：通過介面ServletContextInitializer直接註冊

@SpringBootApplication
public class SpringBootDemo71Application implements ServletContextInitializer{

    public static void main(String[] args) {
        SpringApplication.run(SpringBootDemo71Application.class, args);
    }

    @Override
    public void onStartup(ServletContext servletContext) throws ServletException {
        servletContext.addServlet("customServlet",new CustomServlet()).addMapping("/zzrdemo");
        servletContext.addFilter("customFilter",new CustomFilter()).addMappingForServletNames(EnumSet.of(DispatcherType.REQUEST),true,"customServlet");
        servletContext.addListener(new CustomListener());
    }
}

方法三：在SpringBootApplication使用註解@ServletComponentScan，然後在servlet，filter，listener上增加註解即可：

• servlet上加註解：@WebServlet(value = "/zzrdemo",name = "customServlet")
• filter上加註解：
  @WebFilter(urlPatterns = "/*",filterName = "customFilter")
• listener上加註解：@WebListener