过滤器作用

过滤器用途主要包括：对用户请求进行统一认证、对用户的访问请求进行记录和审核、对用户发送的数据进行过滤或替换、转换图象格式、对响应内容进行压缩以减少传输量、对请求或响应进行加解密处理、触发资源访问事件、对XML的输出应用XSLT等。

init(FilterConfig conf)方法：用于执行过滤器的初始化工作，web容器会在web项目启动时自动调用该方法。

doFilter(ServletRequest request,SerlvetResponse response，FilterChain chain)方法：当请求和响应被过滤器拦截后，都会交给doFilter来处理:其中两个参数分别是被拦截request和response对象，可以使用chain的doFliter方法来放行。

destroy()方法：用于释放关闭Filter对象打开的资源，在web项目关闭时，由web容器自动调用该方法。

注册Filter

父pom文件

<?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>3.1.2</version>-->
        <version>2.2.5.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.chensir</groupId>
    <artifactId>springboot</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>springboot</name>
    <description>springboot</description>
    <properties>
        <java.version>8</java.version>
    </properties>

    <packaging>pom</packaging>

    <modules>
        <module>servlet</module>
    </modules>

    <dependencies>

        <dependency>
            <groupId>com.aliyun</groupId>
            <artifactId>alibaba-dingtalk-service-sdk</artifactId>
            <version>2.0.0</version>
        </dependency>

        <dependency>
            <groupId>cn.hutool</groupId>
            <artifactId>hutool-all</artifactId>
            <version>5.8.3</version>
        </dependency>

<!--        <dependency>-->
<!--            <groupId>org.slf4j</groupId>-->
<!--            <artifactId>slf4j-log4j12</artifactId>-->
<!--            <version>1.7.25</version>-->
<!--        </dependency>-->

        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.22</version>
        </dependency>

        <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>

pom文件

<?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>com.chensir</groupId>
        <artifactId>springboot</artifactId>
        <version>0.0.1-SNAPSHOT</version>
        <relativePath>../pom.xml</relativePath>
    </parent>

    <artifactId>servlet</artifactId>

    <dependencies>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</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>

注解方式

TokenFilter

package com.chensir.javaWeb;

import cn.hutool.core.date.StopWatch;
import cn.hutool.core.util.StrUtil;
import lombok.extern.slf4j.Slf4j;

import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

// 所有api以/api开头都会走此过滤器
@WebFilter("/api/*")
@Slf4j
public class TokenFilter implements Filter {

    /**
     * 过滤器生成的时候调用;过滤前
     * @param filterConfig
     * @throws ServletException
     */
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        Filter.super.init(filterConfig);
    }

    /**
     * 过滤器主要代码;过滤中
     * @param servletRequest
     * @param servletResponse
     * @param filterChain
     * @throws IOException
     * @throws ServletException
     */
    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        // ServletRequest=>HttpServletRequest
        HttpServletRequest request = (HttpServletRequest) servletRequest;
        // ServletResponse=>HttpServletResponse
        HttpServletResponse response = (HttpServletResponse) servletResponse;
        log.info("-------------TokenFilter开始-------------");
//        String token = request.getHeader("token");
        String token = request.getParameter("token");
        log.info("获取到token->{}",token);
        if (StrUtil.isEmpty(token)){
            response.sendRedirect("/logout");
        }

        StopWatch sw = new StopWatch();
        sw.start();
        filterChain.doFilter(servletRequest,servletResponse);
        sw.stop();
        log.info("-------------TokenFilter结束,耗时：{}-------------",sw.getTotalTimeSeconds());
    }

    /**
     * 过滤器销毁的时候调用;过滤后
     */
    @Override
    public void destroy() {
        Filter.super.destroy();
    }
}

LogFilter

package com.chensir.javaWeb;

import lombok.extern.slf4j.Slf4j;

import javax.servlet.*;
import java.io.IOException;

// 所有api以/api开头都会走此过滤器
@WebFilter("/api/*")
@Slf4j
public class LogFilter implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        Filter.super.init(filterConfig);
    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        log.info("-------------LogFilter开始-------------");
        filterChain.doFilter(servletRequest,servletResponse);
        log.info("-------------LogFilter结束-------------");
    }

    @Override
    public void destroy() {
        Filter.super.destroy();
    }
}

Logout

启动类

使用FilterRegistrationBean注册

package com.chensir.config;

import com.chensir.javaWeb.HelloServlet;
import com.chensir.javaWeb.LogFilter;
import com.chensir.javaWeb.ServletListener;
import com.chensir.javaWeb.TokenFilter;
import org.springframework.boot.web.servlet.FilterRegistrationBean;
import org.springframework.boot.web.servlet.ServletListenerRegistrationBean;
import org.springframework.boot.web.servlet.ServletRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class MyWebConfig {

    @Bean
    public ServletRegistrationBean servletRegistrationBean() {
        ServletRegistrationBean servletRegistrationBean = new ServletRegistrationBean();
        servletRegistrationBean.setServlet(new HelloServlet());
        servletRegistrationBean.addUrlMappings("/api/helloBaby");
        return servletRegistrationBean;
    }

    @Bean
    public ServletListenerRegistrationBean servletListenerRegistrationBean() {
        ServletListenerRegistrationBean bean = new ServletListenerRegistrationBean();
        bean.setListener(new ServletListener());
        // 启用
        bean.setEnabled(true);
        return bean;
    }

    @Bean
    public FilterRegistrationBean filterRegistrationBean(){
        FilterRegistrationBean filter = new FilterRegistrationBean();
        filter.setFilter(new TokenFilter());
        filter.addUrlPatterns("/api/*");
        filter.setName("Token过滤器");
        // 值越小 越先执行
        filter.setOrder(0);
        return filter;
    }

    @Bean
    public FilterRegistrationBean logFilterRegistrationBean(){
        FilterRegistrationBean filter = new FilterRegistrationBean();
        filter.setFilter(new LogFilter());
        filter.addUrlPatterns("/api/*");
        filter.setName("log过滤器");
        // 值越小 越先执行
        filter.setOrder(1);
        return filter;
    }
}