做网站时如何给文字做超链接网络服务提供者知道网络用户利用其网络服务

SpringBoot从入门到精通-第6章 过滤器

Filter过滤器是单独的类文件，不写在控制层、服务层、持久层。
写好正确的注解和扫描，程序启动时就会第一时间到过滤器。
过滤器注解：
@WebFilter(“/*”)用于类上，过滤url
@Component和@WebFilter注解一起使用，让主程序能扫描到过滤器
前提是过滤器类实现Filter接口。

一、过滤器简介

二、通过注解配置过滤器

2.1先启动一个简单的Springboot程序
pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd"><modelVersion>4.0.0</modelVersion><parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>3.5.0</version><relativePath/> <!-- lookup parent from repository --></parent><groupId>com.example</groupId><artifactId>_20250611spring_Filter</artifactId><version>0.0.1-SNAPSHOT</version><name>20250611spring_Filter</name><description>20250611spring_Filter</description><url/><licenses><license/></licenses><developers><developer/></developers><scm><connection/><developerConnection/><tag/><url/></scm><properties><java.version>17</java.version></properties><dependencies><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></dependencies><build><plugins><plugin><groupId>org.springframework.boot</groupId><artifactId>spring-boot-maven-plugin</artifactId></plugin></plugins></build></project>

2.2编写控制器类

package com.example._20250611spring_filter.controller;import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.bind.annotation.RestController;@RestController
@ResponseBody
public class FilterController {@RequestMapping("/filter")public String soutFilter(){System.out.println("this is filter");return "This is Filter!";}
}

2.3启动项目后浏览器访问http://127.0.0.1:8080/filter

2.4配置过滤器类

package com.example._20250611spring_filter.filter;import jakarta.servlet.*;
import jakarta.servlet.annotation.WebFilter;
import org.springframework.stereotype.Component;import java.io.FileFilter;
import java.io.IOException;
@WebFilter("/*")
@Component
public class TestFilter implements Filter {@Overridepublic void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {System.out.println("before doFilter() !!!");filterChain.doFilter(servletRequest,servletResponse);System.out.println("after doFilter() !!!");}
}

2.5过滤器内容释义：

• import java.io.FileFilter;注意实现Filter接口时候需要选择与springboot适配的包。
• @WebFilter(“/*”)注解标注要过滤的路径，这里过滤所有
• @Component注解让主程序启动时扫描到过滤器类
• public void doFilter()过滤方法，是Filter接口的方法，必须要实现
• filterChain.doFilter(servletRequest,servletResponse)方法是过滤方法过滤结束后放行，即过滤器过滤完去程序执行任务。是固定写法。
• Filetr接口有3个方法，初始化方法和销毁方法可以不用必须被重写。
• 

2.6测试访问http://127.0.0.1:8080/filter
如果没有filterChain.doFilter(servletRequest,servletResponse);放行，“this is filter”和“after doFilter() !!!”是不会被打印的。

三、实例
用过滤器统计资源访问量
3.1配置过滤器类

package com.example._20250611spring_filter.filter;import jakarta.servlet.*;
import jakarta.servlet.annotation.WebFilter;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import org.springframework.stereotype.Component;import java.io.FileFilter;
import java.io.IOException;
@WebFilter("/filter")
@Component
public class TestFilter implements Filter {@Overridepublic void init(FilterConfig filterConfig) throws ServletException {ServletContext context = filterConfig.getServletContext();context.setAttribute("count",0);}@Overridepublic void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {System.out.println("before doFilter() !!!");HttpServletRequest req = (HttpServletRequest) servletRequest;ServletContext context = req.getServletContext();Integer count = (Integer) context.getAttribute("count");context.setAttribute("count",++count);filterChain.doFilter(servletRequest,servletResponse);System.out.println("after doFilter() !!!");}
}

3.2配置控制器类

package com.example._20250611spring_filter.controller;import jakarta.servlet.ServletContext;
import jakarta.servlet.http.HttpServletRequest;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.bind.annotation.RestController;@RestController
@ResponseBody
public class FilterController {@RequestMapping("/filter")public String soutFilter(HttpServletRequest request){ServletContext context = request.getServletContext();Integer count = (Integer) context.getAttribute("count");return "当前访问量："+count;
//        System.out.println("this is filter");
//        return "This is Filter!";}
}

3.3访问测试

四、通过FilterRegistrationBean类配置过滤器