SpringBoot项目实战（7）：Filter、Listener

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前言
本文为了记录什么
文中涉及的类基本以及作用
基本代码
实现过滤器
- 通过代码注册
- 通过注解实现Filter
实现监听器
- 通过代码注册
- 通过注解实现监听器
说在最后的话
其他相关文章
更多

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);@Overridepublic void destroy() {LOGGER.info("WebAppFilter - 过滤器已销毁...");}@Overridepublic 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);}@Overridepublic 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);@Overridepublic void destroy() {LOGGER.info("WebAppForIndexFilter - 过滤器已销毁...");}@Overridepublic 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);}@Overridepublic 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;@Overridepublic void contextDestroyed(ServletContextEvent arg0) {LOGGER.info("WebAppListener监听器已销毁...");}@Overridepublic 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;
@SpringBootApplication
public class Applaction {/*** @Description 注册webAppFilter* @author zhangyd* @date 2017年4月7日 下午4:37:37 * @return*/@Beanpublic 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*/@Beanpublic 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/filter1
2017-04-07 16:43:38 [com.zyd.servlet.config.filter.WebAppFilter] INFO  - WebAppFilter - Request port：8083
2017-04-07 16:43:38 [com.zyd.servlet.config.filter.WebAppFilter] INFO  - WebAppFilter - Request Method: GET
2017-04-07 16:43:41 [com.zyd.servlet.config.filter.WebAppForIndexFilter] INFO  - WebAppForIndexFilter - Request URL: http://127.0.0.1:8083/servlet/index
2017-04-07 16:43:41 [com.zyd.servlet.config.filter.WebAppForIndexFilter] INFO  - WebAppForIndexFilter - Request port：8083
2017-04-07 16:43:41 [com.zyd.servlet.config.filter.WebAppForIndexFilter] INFO  - WebAppForIndexFilter - Request Method: GET
2017-04-07 16:43:44 [com.zyd.servlet.config.filter.WebAppFilter] INFO  - WebAppFilter - Request URL: http://127.0.0.1:8083/servlet/filter2
2017-04-07 16:43:44 [com.zyd.servlet.config.filter.WebAppFilter] INFO  - WebAppFilter - Request port：8083
2017-04-07 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
@ServletComponentScan
public 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/filter2
2017-04-07 16:52:25 [com.zyd.servlet.config.filter.WebAppFilter] INFO  - WebAppFilter - Request port：8083
2017-04-07 16:52:25 [com.zyd.servlet.config.filter.WebAppFilter] INFO  - WebAppFilter - Request Method: GET
2017-04-07 16:52:29 [com.zyd.servlet.config.filter.WebAppForIndexFilter] INFO  - WebAppForIndexFilter - Request URL: http://127.0.0.1:8083/servlet/index
2017-04-07 16:52:29 [com.zyd.servlet.config.filter.WebAppForIndexFilter] INFO  - WebAppForIndexFilter - Request port：8083
2017-04-07 16:52:29 [com.zyd.servlet.config.filter.WebAppForIndexFilter] INFO  - WebAppForIndexFilter - Request Method: GET
2017-04-07 16:52:29 [com.zyd.servlet.config.filter.WebAppForIndexFilter] INFO  - WebAppForIndexFilter - Request URL: http://127.0.0.1:8083/servlet/index
2017-04-07 16:52:29 [com.zyd.servlet.config.filter.WebAppForIndexFilter] INFO  - WebAppForIndexFilter - Request port：8083
2017-04-07 16:52:29 [com.zyd.servlet.config.filter.WebAppForIndexFilter] INFO  - WebAppForIndexFilter - Request Method: GET
2017-04-07 16:52:33 [com.zyd.servlet.config.filter.WebAppFilter] INFO  - WebAppFilter - Request URL: http://127.0.0.1:8083/servlet/filter1
2017-04-07 16:52:33 [com.zyd.servlet.config.filter.WebAppFilter] INFO  - WebAppFilter - Request port：8083
2017-04-07 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/filter2
2017-04-07 17:00:32 [com.zyd.servlet.config.filter.WebAppFilter] INFO  - WebAppFilter - Request port：8083
2017-04-07 17:00:32 [com.zyd.servlet.config.filter.WebAppFilter] INFO  - WebAppFilter - Request Method: GET
2017-04-07 17:00:32 [com.zyd.servlet.config.filter.WebAppForIndexFilter] INFO  - WebAppForIndexFilter - Request URL: http://127.0.0.1:8083/servlet/filter2
2017-04-07 17:00:32 [com.zyd.servlet.config.filter.WebAppForIndexFilter] INFO  - WebAppForIndexFilter - Request port：8083
2017-04-07 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;
@SpringBootApplication
public class Applaction {@Beanpublic 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 hierarchy
2017-04-07 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

Git源码

码云源码

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SpringBoot项目实战（4）：集成Mybatis
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