springboot使用过滤器，拦截器，监听器

一、过滤器的使用

1.写一个类继承Filter

@WebFilter(filterName="myFilter",urlPatterns={"/*"}) public class AMyFilter2 implements Filter{ @Override public void init(FilterConfig filterConfig) throws ServletException { System.out.println("==========初始化过滤器A"); } @Override public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException { System.out.println("=======进入过滤器2a"); filterChain.doFilter(servletRequest, servletResponse); //放行过滤器 } @Override public void destroy() { } }

注意：拦截器执行的顺序与  filterName="myFilter" 的值有关，按字母排序

也可以通过@Order指定执行顺序，值越小，越先执行

2.启动类加上注解

@ServletComponentScan

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 二、监听器的使用

1.写一个类继承ServletRequestListener

@WebListener public class myListen1 implements ServletRequestListener { @Override public void requestDestroyed(ServletRequestEvent servletRequestEvent) { System.out.println("监听器1销毁"); } @Override public void requestInitialized(ServletRequestEvent servletRequestEvent) { System.out.println("监听器1初始化"); } }

2.启动类加上注解

@ServletComponentScan

三、拦截器的使用

1.写一个类继承HandlerInterceptor

@Component public class MyInterceptor implements HandlerInterceptor{ @Override public boolean preHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o) throws Exception { System.out.println("======请求前拦截器"); return true; } @Override public void postHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, ModelAndView modelAndView) throws Exception { System.out.println("======请求后调用拦截器"); } @Override public void afterCompletion(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) throws Exception { System.out.println("=======拦截器,请求调用完成后回调方法，即在视图渲染完成后回调"); } }

2.写一个配置类注入拦截器

@Configuration public class WebMvcConfigurer extends WebMvcConfigurerAdapter{ @Autowired MyInterceptor myInterceptor; @Override public void addInterceptors(InterceptorRegistry registry) { //注册拦截器 拦截规则 //多个拦截器时 以此添加 执行顺序按添加顺序 registry.addInterceptor(getHandlerInterceptor()); } @Bean public static HandlerInterceptor getHandlerInterceptor() { return new MyInterceptor(); } }

观察过滤器，监听器，拦截器的请求顺序

=======监听器1初始化 2019-05-25 11:42:11.586 INFO 7536 --- [nio-8080-exec-1] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring FrameworkServlet 'dispatcherServlet' 2019-05-25 11:42:11.586 INFO 7536 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet : FrameworkServlet 'dispatcherServlet': initialization started 2019-05-25 11:42:11.612 INFO 7536 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet : FrameworkServlet 'dispatcherServlet': initialization completed in 26 ms =======进入过滤器2a =======进入过滤器 =======进入过滤器2 ======请求前拦截器 测试 ======请求后调用拦截器 =======拦截器,请求调用完成后回调方法，即在视图渲染完成后回调 =======监听器1销毁

四、总结

过滤器：用于属性甄别，对象收集（不可改变过滤对象的属性和行为）

监听器：用于对象监听，行为记录（不可改变监听对象的属性和行为）

拦截器：用于对象拦截，行为干预（可以改变拦截对象的属性和行为）