原创

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

  一: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
	 */
	@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(webAppFilterwebAppForIndexFilter

    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filter1filter2请求,WebAppForIndexFilter 对应过滤index请求

  二: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/filter1xx/servlet/filter2xx/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

  一: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 {
	@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 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()

   二: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


    Github源码


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