JavaWeb三大组件——Filter

港控/mmm° 2023-10-14 15:02 17阅读 0赞

**目录**

过滤器作用

注册Filter

父pom文件

pom文件

注解方式

TokenFilter

LogFilter

Logout

启动类

使用FilterRegistrationBean注册

结果

--------------------

## 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。

![310915a2d2454ce4a56d6aa47f0584dd.png][]

**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 ##

![323bbcf752784ec289cec828e81ee6c2.png][]

### 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>2.2.5.RELEASE</version>
            <relativePath/> 
        </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.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 ###

### 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 ####

![2c6be6f0a07040c29066e18ebe719587.png][]

#### 启动类 ####

![241fc9a251244c42b5443d692acba53a.png][]

### 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;
        }
    }

### 结果 ###

![445296756b3b4a5a9a4077e9e1137362.png][]

注意：filter执行顺序正是根据注册时优先级大小运行；而监听器、过滤器、servlet的执行顺序可由下面这张图理解；

![2bb3fd45b27444de90b9b9f94c19ec72.png][]

[310915a2d2454ce4a56d6aa47f0584dd.png]: https://img-blog.csdnimg.cn/310915a2d2454ce4a56d6aa47f0584dd.png
[323bbcf752784ec289cec828e81ee6c2.png]: https://img-blog.csdnimg.cn/323bbcf752784ec289cec828e81ee6c2.png
[2c6be6f0a07040c29066e18ebe719587.png]: https://img-blog.csdnimg.cn/2c6be6f0a07040c29066e18ebe719587.png
[241fc9a251244c42b5443d692acba53a.png]: https://img-blog.csdnimg.cn/241fc9a251244c42b5443d692acba53a.png
[445296756b3b4a5a9a4077e9e1137362.png]: https://img-blog.csdnimg.cn/445296756b3b4a5a9a4077e9e1137362.png
[2bb3fd45b27444de90b9b9f94c19ec72.png]: https://img-blog.csdnimg.cn/2bb3fd45b27444de90b9b9f94c19ec72.png