springboot监听器，过滤器，拦截器

servlet3.0注解

package com.ethan.springboottest.servlet;
import javax.servlet.annotation.WebServlet;//注意这里导入的包名，导入其他的包会报错
/**
 * @Author: ethan.liu
 * @Date: 2019/11/28 10:16
 */
@WebServlet(name = "user",urlPatterns = "/test")
public class UserServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("--->doGet");
        resp.getWriter().print("hi");
        resp.getWriter().flush();
        resp.getWriter().close();
    }

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

    @Override
    public void destroy() {
        super.destroy();
        System.out.println("--->destroy");
    }
}

启动类要加注解
@ServletComponentScan
不然不起作用
@SpringBootApplication
@ServletComponentScan
public class SpringboottestApplication {
    public static void main(String[] args) {
        SpringApplication.run(SpringboottestApplication.class, args);
    }
}
浏览器访问路径为：
http://localhost:8080/test

监听器

servletContextListener、httpSessionListener、servletRequestListener
常见监听器 servletContextListener,httpSessionListener,servletRequestListner

servletContextListener

项目启动的时候调用走contextInitialized项目被kill掉后走contextDestroyed
所以在contextInitialized我们可以做一些初始化的工作，异步加载点数据等等。

@WebListener
public class ServletContextListener implements javax.servlet.ServletContextListener {
    @Override
    public void contextInitialized(ServletContextEvent sce) {

        System.out.println("ServletContextListener====contextInitialized");
    }

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

servletRequestListner

ServletRequestListener的生命周期为请求开始到请求结束比如发一个
http://localhost:8080/user/test请求会先后调用requestInitialized，requestDestroyed

@WebListener
public class ServletRequestListener implements javax.servlet.ServletRequestListener {
    @Override
    public void requestDestroyed(ServletRequestEvent sre) {
        System.out.println("ServletRequestListener====requestDestroyed");
    }
    @Override
    public void requestInitialized(ServletRequestEvent sre) {
        System.out.println("ServletRequestListener====requestInitialized");
    }
}

httpSessionListener

@WebListener
public class ServletSesstionListener implements HttpSessionListener {
    @Override
    public void sessionCreated(HttpSessionEvent se) {
        System.out.println("ServletSesstionListener===sessionCreated");
    }

    @Override
    public void sessionDestroyed(HttpSessionEvent se) {
        System.out.println("ServletSesstionListener===sessionDestroyed");
    }
}


 @RequestMapping("test")
    public Object test(HttpServletRequest httpServletRequest){
       //如果这里不设置的话sessionCreated不会创建
        httpServletRequest.getSession().setAttribute("123","1234");
        System.out.println("sid="+httpServletRequest.getSession().getId());
        return "test";
    }
    
    //test2和test3输出的id是一样的每次都一样说明session没走创建
    @RequestMapping("test2")
    public Object test1(HttpServletRequest httpServletRequest){
        System.out.println("sid="+httpServletRequest.getSession().getId());
        return "test";
    }
    @RequestMapping("test3")
    public Object test3(HttpServletRequest httpServletRequest){
        System.out.println("sid="+httpServletRequest.getSession().getId());
        return "test";
    }

过滤器

类似于你带票了没带票就不让进带了就进入拦截器开始验票，票通过了可以进入controller处理业务。

@WebFilter("/user/*")
@Configuration
public class MyFilter implements Filter {

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {

    }
    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        HttpServletRequest request = ((HttpServletRequest) servletRequest);
        if (request.getRequestURI().contains("info")){
            filterChain.doFilter(servletRequest,servletResponse);
        }
        servletResponse.getWriter().print("hello");
        servletResponse.getWriter().flush();
        servletResponse.getWriter().close();
    }

    @Override
    public void destroy() {

    }
}


 @RequestMapping("test2")被过滤
    public Object test1(HttpServletRequest httpServletRequest){
        System.out.println("sid="+httpServletRequest.getSession().getId());
        return "test";
    }
    @RequestMapping("info")//通过
    public Object test3(HttpServletRequest httpServletRequest){
        System.out.println("sid="+httpServletRequest.getSession().getId());
        return "test";
    }

拦截器

@Configuration
public class InterceptorConfig implements WebMvcConfigurer {
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        //最后一个路径为/**
        registry.addInterceptor(new MyInterceptor()).addPathPatterns("/user/**");
    }

    @Override
    public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
        FastJsonHttpMessageConverter fastConverter = new FastJsonHttpMessageConverter();
        FastJsonConfig fastJsonConfig = new FastJsonConfig();
        fastJsonConfig.setSerializerFeatures(SerializerFeature.QuoteFieldNames,
                SerializerFeature.PrettyFormat,
                SerializerFeature.WriteEnumUsingToString,
                SerializerFeature.WriteDateUseDateFormat,
                SerializerFeature.DisableCircularReferenceDetect);
        //long转string

        //设置时间
        fastJsonConfig.setDateFormat("yyyy-MM-dd HH:mm:ss");
        fastConverter.setFastJsonConfig(fastJsonConfig);
        converters.add(fastConverter);
    }
}

public class MyInterceptor implements HandlerInterceptor {

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        System.out.println("url---"+request.getRequestURI());
        return true;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {

    }

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

    }
}

configureMessageConverters测试表明configureMessageConverters 全局有效果！preHandle拦截的话对指定路径
这里只对时间格式化，做个简单测试，大家可以下源码自己编译测试
目录其效果
从上面的log显示我们可以看到执行的顺序如下：

ServletContextListener====contextInitialized
ServletRequestListener====requestInitialized
MyFilter---doFilter
MyInterceptor---preHandle
user/info controller方法
ServletRequestListener====requestDestroyed

项目测试源码：https://github.com/suethan/filter_interceptor