# springboot使用拦截器-过滤器-servlet-listener [项目地址](https://github.com/heng1234/springboot2.x/tree/master/inte_filter_servlet)： ## 一、springboot使用拦截器 **一个拦截器，只有preHandle方法返回true，postHandle、afterCompletion才有可能被执行；如果preHandle方法返回false，则该拦截器的postHandle、afterCompletion必然不会被执行。拦截器不是Filter，却实现了Filter的功能，其原理在于：** **所有的拦截器(Interceptor)和处理器(Handler)都注册在HandlerMapping中。** **Spring MVC中所有的请求都是由DispatcherServlet分发的。** **当请求进入DispatcherServlet.doDispatch()时候，首先会得到处理该请求的Handler（即Controller中对应的方法）以及所有拦截该请求的拦截器。拦截器就是在这里被调用开始工作的。** 新建WebMvcConfigurer实现WebMvcConfigurer ```java import com.boot.inte_filter_servlet.interceptor.init.UserInterceptor; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.context.annotation.Configuration; import org.springframework.web.servlet.config.annotation.InterceptorRegistry; import org.springframework.web.servlet.config.annotation.ResourceHandlerRegistry; /** * @author : kaifa * create at: 2019-11-04 18:18 * @description: 拦截器配置 */ @Configuration public class WebMvcConfigurer implements org.springframework.web.servlet.config.annotation.WebMvcConfigurer { @Autowired private UserInterceptor userInterceptor; //配置拦截的资源以及放行的资源 @Override public void addInterceptors(InterceptorRegistry registry) { /** * 拦截器按照顺序执行 */ //拦截Controller所有 /*/** userInterceptor是定义的拦截器 registry.addInterceptor(userInterceptor) //拦截的url /**是所有 .addPathPatterns("/**") //不拦截url .excludePathPatterns("/user/notInit") //放行静态资源 .excludePathPatterns("/img/**","/css/**","/fonts/**","/js/**"); } //配置静态资源的位置 @Override public void addResourceHandlers(ResourceHandlerRegistry registry) { } } ``` 定义拦截器 UserInterceptor实现HandlerInterceptor ```java import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.springframework.stereotype.Component; import org.springframework.web.servlet.HandlerInterceptor; import org.springframework.web.servlet.ModelAndView; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; /** * @author : kaifa * create at: 2019-11-05 10:24 * @description: 拦截器 */ @Component public class UserInterceptor implements HandlerInterceptor { /** * log日志 */ Logger log= LoggerFactory.getLogger(this.getClass()); /** * 预处理回调方法，实现处理器的预处理（如检查登陆），第三个参数为响应的处理器，自定义Controller * 返回值：true表示继续流程（如调用下一个拦截器或处理器）；false表示流程中断（如登录检查失败），不会继续调用其他的拦截器或处理器，此时我们需要通过response来产生响应； */ @Override public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception { log.info("----------拦截器---Controller方法调用之前被拦截，放行..."); return true; } /** * 后处理回调方法，实现处理器的后处理（但在渲染视图之前），此时我们可以通过modelAndView（模型和视图对象）对模型数据进行处理或对视图进行处理，modelAndView也可能为null。 */ @Override public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception { log.info("----------拦截器---Controller方法调用之后被拦截"); } /** * 整个请求处理完毕回调方法，即在视图渲染完毕时回调，如性能监控中我们可以在此记录结束时间并输出消耗时间，还可以进行一些资源清理，类似于try-catch-finally中的finally，但仅调用处理器执行链中 */ @Override public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception { log.info("----------拦截器---日志记录...."); } } ``` controller测试拦截器 ```java import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RestController; /** * @author : kaifa * create at: 2019-11-05 11:08 * @description: 测试拦截器 */ @RestController @RequestMapping("user") public class UserController { @RequestMapping("init") public String init(){ return "init"; } @RequestMapping("notInit") public String notInit(){ return "notInit"; } } ``` 访问 ![image-20191105174702984](/files/-Lsy_gPWJKdE62I_0pEw) 访问 ## 二、springboot使用过滤器注解版 在启动类加上@ServletComponentScan注解 UserWebFilter ```java import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.springframework.core.annotation.Order; import javax.servlet.*; import javax.servlet.annotation.WebFilter; import javax.servlet.http.HttpServletRequest; import java.io.IOException; /** * @author : kaifa * create at: 2019-11-05 17:59 * @description: 使用拦截器注解版 */ @Order(1)//优先级 @WebFilter(filterName = "userfilter",urlPatterns = "/*") public class UserWebFilter implements Filter { /** * log日志 */ Logger log= LoggerFactory.getLogger(this.getClass()); /** * 该方法由 web 容器调用,以指示 Filter 已经投入使用。servlet容器在实例化过滤器之后调用init方法一次。在要求过滤器执行任何过滤工作之前，init方法必须成功完成。当 init 方法出现以下情况时 Filter 将不生效: * a.抛出了 ServletException 异常; * b.在一段时间内没有返回结果(超时了) * @param filterConfig * @throws ServletException */ @Override public void init(FilterConfig filterConfig) throws ServletException { log.info("调用init()方法初始化实例，在项目启动时候调用一次"); } @Override public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException { HttpServletRequest request = (HttpServletRequest) servletRequest; String requestURI = request.getRequestURI(); StringBuffer requestURL = request.getRequestURL(); log.info("requestURI:" +requestURI+" "+"requestURL:"+requestURL); log.info("每一请求只调用方法的doFilter()进行真正的过滤处理，每次发出请求都会调用"); filterChain.doFilter(request, servletResponse); } @Override public void destroy() { log.info("停止服务器调用destroy()方法，销毁实例，释放资源，项目停止时销毁一次"); } } ``` 测试过滤器 ```java import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RestController; /** * @author : kaifa * create at: 2019-11-05 18:23 * @description: 测试过滤器 */ @RestController @RequestMapping("filter") public class FilterController { @RequestMapping("filterTest") public String filterTest(){ return "this filter"; } } ``` 启动项目 ![image-20191105183357048](/files/-Lsy_gPiY0p4-BETrsLT) 访问url ![image-20191105183411421](/files/-Lsy_gPp-3ZkCJX50hNi) 停止工程 ![image-20191105183439661](/files/-Lsy_gPuqtLH5OYZb0r9) ![image-20191106093443990](/files/-Lsy_gQ-tE9UhAbZzTsF) ## 三、springboot使用servlet UserServlet ```java import lombok.extern.slf4j.Slf4j; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.IOException; /** * @author : kaifa * create at: 2019-11-06 09:50 * @description: servlet */ @WebServlet(urlPatterns = "/user") @Slf4j public class UserServlet extends HttpServlet { @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { log.info("user--doGet方法"); resp.setHeader("Content-Type","text/html;charset=UTF-8"); resp.getOutputStream().write("user--doGet方法".getBytes("UTF-8")); } @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { doGet(req, resp); } } ``` 访问 ![image-20191106103203218](/files/-Lsy_gQ2oeH_A0hxMFy7) ## 四、springboot使用listener ```java import lombok.extern.slf4j.Slf4j; import javax.servlet.annotation.WebListener; import javax.servlet.http.HttpSessionEvent; import javax.servlet.http.HttpSessionListener; import java.util.concurrent.atomic.AtomicInteger; /** * @author : kaifa * create at: 2019-11-06 09:57 * @description: 监听器session * * * */ @Slf4j @WebListener public class MyListener implements HttpSessionListener { private AtomicInteger onLineCount = new AtomicInteger(0); /** * ServletContextListener -- 监听servletContext对象的创建以及销毁 * * contextInitialized(ServletContextEvent arg0) -- 创建时执行 * * contextDestroyed(ServletContextEvent arg0) -- 销毁时执行 * * HttpSessionListener -- 监听session对象的创建以及销毁 * * sessionCreated(HttpSessionEvent se) -- 创建时执行 * * sessionDestroyed(HttpSessionEvent se) -- 销毁时执行 * * ServletRequestListener -- 监听request对象的创建以及销毁 * * requestInitialized(ServletRequestEvent sre) -- 创建时执行 * * requestDestroyed(ServletRequestEvent sre) -- 销毁时执行 * * ServletContextAttributeListener -- 监听servletContext对象中属性的改变 * * attributeAdded(ServletContextAttributeEvent event) -- 添加属性时执行 * * attributeReplaced(ServletContextAttributeEvent event) -- 修改属性时执行 * * attributeRemoved(ServletContextAttributeEvent event) -- 删除属性时执行 * * HttpSessionAttributeListener --监听session对象中属性的改变 * * attributeAdded(HttpSessionBindingEvent event) -- 添加属性时执行 * * attributeReplaced(HttpSessionBindingEvent event) -- 修改属性时执行 * * attributeRemoved(HttpSessionBindingEvent event) -- 删除属性时执行 * * ServletRequestAttributeListener --监听request对象中属性的改变 * * attributeAdded(ServletRequestAttributeEvent srae) -- 添加属性时执行 * * attributeReplaced(ServletRequestAttributeEvent srae) -- 修改属性时执行 * * attributeRemoved(ServletRequestAttributeEvent srae) -- 删除属性时执行 * */ @Override public void sessionCreated(HttpSessionEvent se) { se.getSession().getServletContext().setAttribute("onLineCount", onLineCount.incrementAndGet()); log.info("session初始化完成"); } @Override public void sessionDestroyed(HttpSessionEvent se) { log.info("session销毁"); se.getSession().getServletContext().setAttribute("onLineCount", onLineCount.decrementAndGet()); } } ``` 下一章:[springboot中使用异步调用(线程池)](/hlvy/async.md) --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. 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