详解IDEA中SpringBoot整合Servlet三大组件的过程

/*
	在config文件夹下编写配置类
 实现WebMvcConfigurer接口，扩展MVC功能
 测试前将LoginController控制类注释，更好的观察效果
 */
@Configuration
public class MyMVCConfig implements WebMvcConfigurer {
 //添加视图管理
 @Override
 public void addViewControllers(ViewControllerRegistry registry) {
  // 请求toLoginPage映射路径或者login.html页面都会自动映射到login.html页面
  registry.addViewController("/toLoginPage").setViewName("login");
  registry.addViewController("/login.html").setViewName("login");
 }
}

/*
 自定义一个拦截器类，实现简单的拦截业务
 */
@Configuration
public class MyInterceptor implements HandlerInterceptor {
 @Override
 public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
  // 用户请求/admin开头路径时，判断用户是否登录
  String uri = request.getRequestURI();
  Object loginUser = request.getSession().getAttribute("loginUser");
  if(uri.startsWith("/admin")&&null==loginUser){
   response.sendRedirect("/toLoginPage");
   return false;
  }
  return true;
 }

 @Override
 public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler,@Nullable ModelAndView modelAndView) throws Exception {
  //向request域中存放当前年份用于页面动态展示
  request.setAttribute("currentYear", Calendar.getInstance().get(Calendar.YEAR));
 }

 @Override
 public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {

 }
}

 @Autowired
 private MyInterceptor myInterceptor;
 //添加拦截器管理
 @Override
 public void addInterceptors(InterceptorRegistry registry) {
  registry.addInterceptor(myInterceptor)
    .addPathPatterns("/**")
    .excludePathPatterns("/login.html");
 }

/*
 自定义Servlet类
 使用@Component注解将MyServlet类作为组件注入Spring容器。该类继承自HTTPServlet，
 通过HttpServletResponse对象向页面输出"hello MyServlet"
 */
@Component
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 {
  resp.getWriter().write("hello MyServlet");
 }
}

/*
 嵌入式Servlet容器三大组件配置
 @Configuration注解将该类标注为配置类，getServlet()方法用于注册自定义MyServlet，
 返回ServletRegistrationBean类型的Bean对象
 */
@Configuration
public class ServletConfig {
 // 注册Servlet组件
 @Bean
 public ServletRegistrationBean<javax.servlet.Servlet> getServlet(MyServlet myServlet){
  return new ServletRegistrationBean<javax.servlet.Servlet>(myServlet,"/myServlet");
 }
}

/*
 自定义Filter类
 使用@Component注解将当前MyFilter类作为组件注入到Spring容器中
 MyFilter类实现Filter接口，重写如下三个方法，在doFilter()方法中想控制台打印"hello MyFilter"
 */
@Component
public class MyFilter implements Filter {
 @Override
 public void init(FilterConfig filterConfig) throws ServletException {
 }
 @Override
 public void destroy() {
 }
 @Override
 public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
  System.out.println("hello MyFilter");
  filterChain.doFilter(servletRequest,servletResponse);
 }
}

 //注册Filter组件
 @Bean
 public FilterRegistrationBean<javax.servlet.Filter> getFilter(MyFilter myFilter){
  FilterRegistrationBean<javax.servlet.Filter> registrationBean = new FilterRegistrationBean<>(myFilter);
  registrationBean.setUrlPatterns(Arrays.asList("/toLoginPage","/myFilter"));
  return registrationBean;
 }

/*
 自定义Listener类
 */
@Component
public class MyListener implements ServletContextListener {
 @Override
 public void contextInitialized(ServletContextEvent sce) {
  System.out.println("contextInitialized ...");
 }

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

 //注册Listener组件
 @Bean
 public ServletListenerRegistrationBean<java.util.EventListener> getServletListener(MyListener myListener){
  return new ServletListenerRegistrationBean<>(myListener);
 }