SpringBoot项目实战（7）：Filter、Listener

前言

过滤器(Filter)是实现了javax.servlet.Filter接口的服务器端程序，主要的用途是过滤字符编码、做一些业务逻辑判断等。它是随web应用启动而启动的，只初始化一次，在web应用停止的时候才被销毁。
监听器(Listener)是实现了javax.servlet.ServletContextListener 接口的服务器端程序，它也是随web应用的启动而启动，只初始化一次，随web应用的停止而销毁。主要作用是： 做一些初始化的内容设置一些基本的内容，比如一些参数或者是一些固定的对象等。

springboot中使用过#滤#器(Filter)和监#听#器(Listener)有两种方式

第一种：代码注册（FilterRegistrationBean 和 ServletListenerRegistrationBean）

第二种：注解实现（SpringBootApplication上使用@ServletComponentScan ，Filter、Listener可以直接通过 @WebFilter、@WebListener 注解自动注册。）

本文为了记录什么？

一：通过两种方式进行使用过滤器和监听器

二：了解过滤器的过滤规则和过滤优先级

文中涉及的类(基本)以及作用

一： WebAppFilter过滤 filter1和 filter2请求

二： WebAppForIndexFilter过滤 index请求

三：ServletController基本控制类，类中index 、filter1、filter2三种请求，命名空间为”/servlet”

四：WebAppListener监听器

基本代码

WebAppFilter 类

package com.zyd.servlet.config.filter;import java.io.IOException;import java.util.Date;import javax.servlet.Filter;import javax.servlet.FilterChain;import javax.servlet.FilterConfig;import javax.servlet.ServletException;import javax.servlet.ServletRequest;import javax.servlet.ServletResponse;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import org.slf4j.Logger;import org.slf4j.LoggerFactory;/** * @Description  * @author zhangyd * @date 2017年4月7日 下午4:37:11  * @version V1.0 * @since JDK ： 1.7 * @modify                  * @Review */public class WebAppFilter implements Filter {    private static final Logger LOGGER = LoggerFactory.getLogger(WebAppFilter.class);    @Override    public void destroy() {        LOGGER.info("WebAppFilter - 过滤器已销毁...");    }    @Override    public void doFilter(ServletRequest arg0, ServletResponse arg1, FilterChain arg2)            throws IOException, ServletException {        HttpServletRequest request = (HttpServletRequest) arg0;        LOGGER.info("WebAppFilter - Request URL: {}", request.getRequestURL().toString());        LOGGER.info("WebAppFilter - Request port：{}", request.getServerPort());        LOGGER.info("WebAppFilter - Request Method: {}", request.getMethod());        HttpServletResponse response = (HttpServletResponse) arg1;        response.setHeader("Current-Path", request.getServletPath());        response.setHeader("My-Name", "MeiNanzi");        arg2.doFilter(arg0, arg1);    }    @Override    public void init(FilterConfig arg0) throws ServletException {        LOGGER.info("WebAppFilter - {}初始化过滤器...", new Date());    }}

WebAppForIndexFilter 类

package com.zyd.servlet.config.filter;import java.io.IOException;import java.util.Date;import javax.servlet.Filter;import javax.servlet.FilterChain;import javax.servlet.FilterConfig;import javax.servlet.ServletException;import javax.servlet.ServletRequest;import javax.servlet.ServletResponse;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import org.slf4j.Logger;import org.slf4j.LoggerFactory;/** * @Description  * @author zhangyd * @date 2017年4月7日 下午4:37:11  * @version V1.0 * @since JDK ： 1.7 * @modify                  * @Review */public class WebAppForIndexFilter implements Filter {    private static final Logger LOGGER = LoggerFactory.getLogger(WebAppForIndexFilter.class);    @Override    public void destroy() {        LOGGER.info("WebAppForIndexFilter - 过滤器已销毁...");    }    @Override    public void doFilter(ServletRequest arg0, ServletResponse arg1, FilterChain arg2)            throws IOException, ServletException {        HttpServletRequest request = (HttpServletRequest) arg0;        LOGGER.info("WebAppForIndexFilter - Request URL: {}", request.getRequestURL().toString());        LOGGER.info("WebAppForIndexFilter - Request port：{}", request.getServerPort());        LOGGER.info("WebAppForIndexFilter - Request Method: {}", request.getMethod());        HttpServletResponse response = (HttpServletResponse) arg1;        response.setHeader("Current-Path", request.getServletPath());        response.setHeader("My-Name", "MeiNanzi");        arg2.doFilter(arg0, arg1);    }    @Override    public void init(FilterConfig arg0) throws ServletException {        LOGGER.info("WebAppForIndexFilter - {}初始化过滤器...", new Date());    }}

ServletController 类

package com.zyd.servlet.controller;import java.util.Date;import org.springframework.web.bind.annotation.RequestMapping;import org.springframework.web.bind.annotation.RestController;/** * @Description  * @author zhangyd * @date 2017年4月7日 下午4:37:11  * @version V1.0 * @since JDK ： 1.7 * @modify                  * @Review */@RestController@RequestMapping("/servlet")public class ServletController {    @RequestMapping("/index")    public Object index() {        return new Date() + " - index";    }    @RequestMapping("/filter1")    public Object filter1() {        return new Date() + " - filter1";    }    @RequestMapping("/filter2")    public Object filter2() {        return new Date() + " - filter2";    }}

WebAppListener 类

package com.zyd.servlet.config.listener;import javax.servlet.ServletContext;import javax.servlet.ServletContextEvent;import javax.servlet.ServletContextListener;import javax.servlet.annotation.WebListener;import org.slf4j.Logger;import org.slf4j.LoggerFactory;public class WebAppListener implements ServletContextListener {    private static final Logger LOGGER = LoggerFactory.getLogger(WebAppListener.class);     public static ServletContext context;    @Override    public void contextDestroyed(ServletContextEvent arg0) {        LOGGER.info("WebAppListener监听器已销毁...");    }    @Override    public void contextInitialized(ServletContextEvent arg0) {        LOGGER.info("WebAppListener监听器开始初始化...");        context = arg0.getServletContext();        LOGGER.info("WebAppListener监听器初始化完成...");    }}

POM.xml 中需要的依赖

<!--支持 Web 应用开发，包含 Tomcat 和 spring-mvc --><dependency>    <groupId>org.springframework.boot</groupId>    <artifactId>spring-boot-starter-web</artifactId></dependency><dependency>    <groupId>org.springframework.boot</groupId>    <artifactId>spring-boot-starter-test</artifactId>    <scope>test</scope></dependency>

实现过滤器

通过代码注册

在Applaction启动类中添加以下代码

package com.zyd.servlet;import java.util.ArrayList;import java.util.List;import org.springframework.boot.SpringApplication;import org.springframework.boot.autoconfigure.SpringBootApplication;import org.springframework.boot.web.servlet.FilterRegistrationBean;import org.springframework.boot.web.servlet.ServletComponentScan;import org.springframework.context.annotation.Bean;import com.zyd.servlet.config.filter.WebAppFilter;import com.zyd.servlet.config.filter.WebAppForIndexFilter;@SpringBootApplicationpublic class Applaction {    /**     * @Description 注册webAppFilter     * @author zhangyd     * @date 2017年4月7日 下午4:37:37      * @return     */    @Bean    public FilterRegistrationBean webAppFilterRegistrationBean() {         FilterRegistrationBean registrationBean = new FilterRegistrationBean();         registrationBean.setName("webAppFilter");         WebAppFilter webAppFilter = new WebAppFilter();         registrationBean.setFilter(webAppFilter);         registrationBean.setOrder(0);         List<String> urlList = new ArrayList<String>();         urlList.add("/servlet/filter1");         urlList.add("/servlet/filter2");         registrationBean.setUrlPatterns(urlList);         return registrationBean;    }    /**     * @Description 注册webAppForIndexFilter     * @author zhangyd     * @date 2017年4月7日 下午4:37:37      * @return     */    @Bean    public FilterRegistrationBean webAppForIndexFilterRegistrationBean() {         FilterRegistrationBean registrationBean = new FilterRegistrationBean();         registrationBean.setName("webAppForIndexFilter");         WebAppForIndexFilter webAppForIndexFilter = new WebAppForIndexFilter();         registrationBean.setFilter(webAppForIndexFilter);         registrationBean.setOrder(-1);         List<String> urlList = new ArrayList<String>();         urlList.add("/servlet/index");         registrationBean.setUrlPatterns(urlList);         return registrationBean;    }    public static void main(String[] args) {        SpringApplication.run(Applaction.class, args);    }}

通过以上，即已经配置好了两个过滤器（webAppFilter和webAppForIndexFilter）

启动并访问(xx/servlet/filter1、xx/servlet/filter2、xx/servlet/index)，查看控制台打印内容

2017-04-07 16:43:38 [com.zyd.servlet.config.filter.WebAppFilter] INFO  - WebAppFilter - Request URL: http://127.0.0.1:8083/servlet/filter12017-04-07 16:43:38 [com.zyd.servlet.config.filter.WebAppFilter] INFO  - WebAppFilter - Request port：80832017-04-07 16:43:38 [com.zyd.servlet.config.filter.WebAppFilter] INFO  - WebAppFilter - Request Method: GET2017-04-07 16:43:41 [com.zyd.servlet.config.filter.WebAppForIndexFilter] INFO  - WebAppForIndexFilter - Request URL: http://127.0.0.1:8083/servlet/index2017-04-07 16:43:41 [com.zyd.servlet.config.filter.WebAppForIndexFilter] INFO  - WebAppForIndexFilter - Request port：80832017-04-07 16:43:41 [com.zyd.servlet.config.filter.WebAppForIndexFilter] INFO  - WebAppForIndexFilter - Request Method: GET2017-04-07 16:43:44 [com.zyd.servlet.config.filter.WebAppFilter] INFO  - WebAppFilter - Request URL: http://127.0.0.1:8083/servlet/filter22017-04-07 16:43:44 [com.zyd.servlet.config.filter.WebAppFilter] INFO  - WebAppFilter - Request port：80832017-04-07 16:43:44 [com.zyd.servlet.config.filter.WebAppFilter] INFO  - WebAppFilter - Request Method: GET

可以看到WebAppFilter对应过滤filter1和filter2请求，WebAppForIndexFilter对应过滤index请求

通过注解实现Filter

WebAppFilter修改为

// 添加这一段注解@WebFilter(filterName = "WebAppFilter", urlPatterns = { "/servlet/filter1","/servlet/filter2" })public class WebAppFilter implements Filter {    ...}

WebAppForIndexFilter修改为

// 添加这一段注解@WebFilter(filterName = "WebAppForIndexFilter", urlPatterns = { "/servlet/index" })public class WebAppForIndexFilter implements Filter {    ...}

Applaction修改为

import org.springframework.boot.SpringApplication;import org.springframework.boot.autoconfigure.SpringBootApplication;@SpringBootApplication// 添加下面这个注解@ServletComponentScanpublic class Applaction {    public static void main(String[] args) {        SpringApplication.run(Applaction.class, args);    }}

重新启动Applaction并访问(xx/servlet/filter1、xx/servlet/filter2、xx/servlet/index)，查看控制台打印内容

2017-04-07 16:52:25 [com.zyd.servlet.config.filter.WebAppFilter] INFO  - WebAppFilter - Request URL: http://127.0.0.1:8083/servlet/filter22017-04-07 16:52:25 [com.zyd.servlet.config.filter.WebAppFilter] INFO  - WebAppFilter - Request port：80832017-04-07 16:52:25 [com.zyd.servlet.config.filter.WebAppFilter] INFO  - WebAppFilter - Request Method: GET2017-04-07 16:52:29 [com.zyd.servlet.config.filter.WebAppForIndexFilter] INFO  - WebAppForIndexFilter - Request URL: http://127.0.0.1:8083/servlet/index2017-04-07 16:52:29 [com.zyd.servlet.config.filter.WebAppForIndexFilter] INFO  - WebAppForIndexFilter - Request port：80832017-04-07 16:52:29 [com.zyd.servlet.config.filter.WebAppForIndexFilter] INFO  - WebAppForIndexFilter - Request Method: GET2017-04-07 16:52:29 [com.zyd.servlet.config.filter.WebAppForIndexFilter] INFO  - WebAppForIndexFilter - Request URL: http://127.0.0.1:8083/servlet/index2017-04-07 16:52:29 [com.zyd.servlet.config.filter.WebAppForIndexFilter] INFO  - WebAppForIndexFilter - Request port：80832017-04-07 16:52:29 [com.zyd.servlet.config.filter.WebAppForIndexFilter] INFO  - WebAppForIndexFilter - Request Method: GET2017-04-07 16:52:33 [com.zyd.servlet.config.filter.WebAppFilter] INFO  - WebAppFilter - Request URL: http://127.0.0.1:8083/servlet/filter12017-04-07 16:52:33 [com.zyd.servlet.config.filter.WebAppFilter] INFO  - WebAppFilter - Request port：80832017-04-07 16:52:33 [com.zyd.servlet.config.filter.WebAppFilter] INFO  - WebAppFilter - Request Method: GET

到此为止就通过两种方式实现了Filter功能，这儿可以思考一个个问题

如果webAppFilter和webAppForIndexFilter都过滤了xx/servlet/filter2请求，具体实现是什么样的？谁在前谁在后？（吐槽：想不到什么业务场景会需要这种需求）可否手动控制过滤器的过滤顺序？

在webAppForIndexFilter中修改一下注解，让其也过滤filter2请求

@WebFilter(filterName = "WebAppForIndexFilter", urlPatterns = { "/servlet/index","/servlet/filter2" })

重启再次访问filter2

2017-04-07 17:00:32 [com.zyd.servlet.config.filter.WebAppFilter] INFO  - WebAppFilter - Request URL: http://127.0.0.1:8083/servlet/filter22017-04-07 17:00:32 [com.zyd.servlet.config.filter.WebAppFilter] INFO  - WebAppFilter - Request port：80832017-04-07 17:00:32 [com.zyd.servlet.config.filter.WebAppFilter] INFO  - WebAppFilter - Request Method: GET2017-04-07 17:00:32 [com.zyd.servlet.config.filter.WebAppForIndexFilter] INFO  - WebAppForIndexFilter - Request URL: http://127.0.0.1:8083/servlet/filter22017-04-07 17:00:32 [com.zyd.servlet.config.filter.WebAppForIndexFilter] INFO  - WebAppForIndexFilter - Request port：80832017-04-07 17:00:32 [com.zyd.servlet.config.filter.WebAppForIndexFilter] INFO  - WebAppForIndexFilter - Request Method: GET

其实这种是默认的顺序，即两个类谁先被编译则谁在过滤顺序上就优先（不信的话可以把两个过滤器的名字改一下）

可以通过@Order进行控制过滤器的执行顺序

/* * 定义执行的优先级，数字越低，优先级越高 */@Order(-5)

实现监听器

通过代码注册

在Applaction启动类中添加以下代码

package com.zyd.servlet;import org.springframework.boot.SpringApplication;import org.springframework.boot.autoconfigure.SpringBootApplication;import org.springframework.boot.web.servlet.ServletListenerRegistrationBean;import org.springframework.context.annotation.Bean;import com.zyd.servlet.config.listener.WebAppListener;@SpringBootApplicationpublic class Applaction {    @Bean    public ServletListenerRegistrationBean<WebAppListener> servletListenerRegistrationBean() {        ServletListenerRegistrationBean<WebAppListener> servletListenerRegistrationBean = new ServletListenerRegistrationBean<WebAppListener>();        servletListenerRegistrationBean.setListener(new WebAppListener());        return servletListenerRegistrationBean;    }    public static void main(String[] args) {        SpringApplication.run(Applaction.class, args);    }}

启动Applaction查看控制台信息

017-04-07 17:13:28 [org.springframework.boot.web.servlet.ServletRegistrationBean] INFO  - Mapping servlet: 'dispatcherServlet' to [/]2017-04-07 17:13:28 [org.springframework.boot.web.servlet.AbstractFilterRegistrationBean] INFO  - Mapping filter: 'characterEncodingFilter' to: [/*]2017-04-07 17:13:28 [org.springframework.boot.web.servlet.AbstractFilterRegistrationBean] INFO  - Mapping filter: 'hiddenHttpMethodFilter' to: [/*]2017-04-07 17:13:28 [org.springframework.boot.web.servlet.AbstractFilterRegistrationBean] INFO  - Mapping filter: 'httpPutFormContentFilter' to: [/*]2017-04-07 17:13:28 [org.springframework.boot.web.servlet.AbstractFilterRegistrationBean] INFO  - Mapping filter: 'requestContextFilter' to: [/*]2017-04-07 17:13:28 [com.zyd.servlet.config.listener.WebAppListener] INFO  - WebAppListener监听器开始初始化...2017-04-07 17:13:28 [com.zyd.servlet.config.listener.WebAppListener] INFO  - WebAppListener监听器初始化完成...2017-04-07 17:13:28 [org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter] INFO  - Looking for @ControllerAdvice: org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext@32c57076: startup date [Fri Apr 07 17:13:24 CST 2017]; root of context hierarchy2017-04-07 17:13:28 [org.springframework.web.servlet.handler.AbstractHandlerMethodMapping$MappingRegistry] INFO  - Mapped "{[/servlet/index]}" onto public java.lang.Object com.zyd.servlet.controller.ServletController.index()2017-04-07 17:13:28 [org.springframework.web.servlet.handler.AbstractHandlerMethodMapping$MappingRegistry] INFO  - Mapped "{[/servlet/filter1]}" onto public java.lang.Object com.zyd.servlet.controller.ServletController.filter1()2017-04-07 17:13:28 [org.springframework.web.servlet.handler.AbstractHandlerMethodMapping$MappingRegistry] INFO  - Mapped "{[/servlet/filter2]}" onto public java.lang.Object com.zyd.servlet.controller.ServletController.filter2()

通过注解实现监听器

方式和过滤器的实现方式基本一致，在Applaction启动类中添加@ServletComponentScan注解，并且在WebAppListener类中添加@WebListener注解

到此就完成了监听器和过滤器的两种实现方式。

说在最后的话

如有不对的地方或者需要补充的地方，欢迎留言告知。

感谢生命中遇到的每一个人，感谢每一个给自己压力的人，感谢每一个恨自己的人

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