一过滤器的作用和概述

1.1 简述

人--->检票员（filter）---> 电影院。

注意：配置多个filter的时候，要设置编号id，值越小，优先级越高，越先执行。

在3.0之后新增@WebFilter注解，当使用注解配置多个Filter时，用户无法控制其执行顺序，此时Filter过滤的顺序是按照Filter的类名来控制的，按自然排序的规则。

1.2 使用场景

场景：权限控制、用户登录(非前端后端分离场景)等，过滤非法登录

过滤器： springboot的filter 过滤器的使用_健康平安的活着的专栏-CSDN博客

监听器： springboot之HttpSessionListener的用法创建，销毁_健康平安的活着的专栏-CSDN博客_httpsessionlistener

拦截器： springboot整合拦截器intercepter_健康平安的活着的专栏-CSDN博客_springboot 拦截器

二自定义过滤的两种方式

2.1 工程结构

2.2 配置pom文件

 <!--spring boot的启动类 --><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><!-- thymeleaf的启动器 --><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-thymeleaf</artifactId></dependency>

2.3 第一种方式

1.启动类里面增加 @ServletComponentScan，进行扫描
2.新建一个Filter类，implements Filter，并实现对应的接口
3. @WebFilter 标记一个类为filter，被spring进行扫描
urlPatterns：拦截规则，支持正则

4.控制chain.doFilter的方法的调用，来实现是否通过放行还是不放行，

如果放行： FilterChain.dofilter(res,rep);

如果不放行：调转到指定页面web应用resp.sendRedirect("/index.html"); return

2.3.1 启动类增加注解

package com.ljf.spring.boot.demo.spt.filter;import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.web.servlet.ServletComponentScan;/*** SpringBoot整合Filter 方式一**/
@SpringBootApplication
@ServletComponentScan
public class App 
{public static void main( String[] args ){SpringApplication.run(App.class, args);}
}

2.3.2 定义一个filter类

package com.ljf.spring.boot.demo.spt.filter.filter;import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import java.io.IOException;
import java.util.logging.LogRecord;
/***SpringBoot整合Filter 方式一*<filter>*	<filter-name>FirstFilter</filter-name>*	<filter-class>com.bjsxt.filter.FirstFilter</filter-class>*</filter>*<filter-mapping>*	<filter-name>FirstFilter</filter-name>*	<url-pattern>/first</url-pattern>*</filter-mapping>*/
@WebFilter(filterName="FirstFilter",urlPatterns="/first")
public class LoginFilter  implements Filter{// @Overridepublic boolean isLoggable(LogRecord record) {return false;}@Overridepublic void init(FilterConfig filterConfig) throws ServletException {}@Overridepublic void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {System.out.println("进入Filter");filterChain.doFilter(servletRequest, servletResponse);System.out.println("离开Filter");}@Overridepublic void destroy() {}
}

2.3.3. 演示

2.4 第二种方式

2.4.1 自定义fitler类

package com.ljf.spring.boot.demo.spt.filter.filter;import java.io.IOException;import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
/*** *SpringBoot整合Filter 方式二**/
public class SecondFilter implements Filter {@Overridepublic void destroy() {// TODO Auto-generated method stub}@Overridepublic void doFilter(ServletRequest arg0, ServletResponse arg1, FilterChain arg2)throws IOException, ServletException {System.out.println("进入SecondFilter");arg2.doFilter(arg0, arg1);System.out.println("离开SecondFilter");}@Overridepublic void init(FilterConfig arg0) throws ServletException {// TODO Auto-generated method stub}
}

2.4.2 启动类

package com.ljf.spring.boot.demo.spt.filter;import com.ljf.spring.boot.demo.spt.filter.filter.SecondFilter;
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;/*** SpringBoot整合Filter方式二*/
@SpringBootApplication
public class App2 {public static void main(String args[]){SpringApplication.run(App.class, args);}/*** 注册Filter*/@Beanpublic FilterRegistrationBean getFilterRegistrationBean(){FilterRegistrationBean bean = new FilterRegistrationBean(new SecondFilter());//bean.addUrlPatterns(new String[]{"*.do","*.jsp"});bean.addUrlPatterns("/second");return bean;}
}

2.4.3 访问

2.5 过滤器的小案例

2.5.1 场景描述

自定义一个过滤器：对路径中含有api字样且userName为xm的请求则放过进行，否则其他情况进行拦截。

2.5.2 工程结构

2.5.3 pom文件

  <!--spring boot的启动类 --><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><!-- thymeleaf的启动器 --><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-thymeleaf</artifactId></dependency>

2.5.4 resources目录下静态文件

1.templates目录下：

2.static 目录下：

2.5.5 controller层

package com.ljf.spring.boot.demo.controller;import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;/*** @ClassName: UserController* @Description: TODO* @Author: liujianfu* @Date: 2021/04/01 10:26:05 * @Version: V1.0**/
@Controller
public class UserController {@RequestMapping("/api/show")public String showName(String userName,Model model){System.out.println("进入controller层了!!!"+userName);model.addAttribute("name",userName);return "index";//跳转到指定页面}}

2.5.6 自定义过滤器

package com.ljf.spring.boot.demo.filter;import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;/*** @ClassName: UserLoginFilter* @Description: TODO* @Author: liujianfu* @Date: 2021/04/01 10:28:14 * @Version: V1.0**//***SpringBoot整合Filter 方式一*<filter>*	<filter-name>loginFilter</filter-name>*	<filter-class>com.ljf.spring.boot.demo.spt.filter.filter.UserLoginFilter</filter-class>*</filter>*<filter-mapping>*	<filter-name>loginFilter</filter-name>*	<url-pattern>/api/*</url-pattern>*</filter-mapping>*/
@WebFilter(urlPatterns = "/api/*", filterName = "loginFilter")
public class UserLoginFilter implements Filter {/*** 容器加载的时候调用*/@Overridepublic void init(FilterConfig filterConfig) throws ServletException {System.out.println("=================init loginFilter=============");}/*** 请求被拦截的时候进行调用*/@Overridepublic void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {System.out.println("doFilter loginFilter");HttpServletRequest req = (HttpServletRequest) servletRequest;HttpServletResponse resp = (HttpServletResponse) servletResponse;String username = req.getParameter("userName");System.out.println("获取用户名:"+username);if ("xm".equals(username)) {System.out.println("======");filterChain.doFilter(servletRequest,servletResponse);} else {resp.sendRedirect("/login.html");//重定向不到templates目录下页面，必须走后端一下跳转到指定页面才行// req.getRequestDispatcher("/").forward(req,resp);return;}}/*** 容器被销毁的时候被调用*/@Overridepublic void destroy() {System.out.println("=========================destroy loginFilter=====================");}}

2.5.7 启动类

注解启动类添加注解：@ServletComponentScan //添加过滤器使用

package com.ljf.spring.boot.demo;import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.web.servlet.ServletComponentScan;/*** Hello world!**/
@SpringBootApplication
@ServletComponentScan   //添加过滤器使用
public class App
{public static void main( String[] args ){SpringApplication.run(App.class, args);System.out.println("用户登录=====");}
}