过滤器和监听器

1、过滤器Filter

作用是防止SQL注入、参数过滤、防止页面攻击、空参数矫正、Token校验、Session验证、点击率统计等等；

使用Filter的步骤

1. 新建类，实现Filter抽象类；
2. 重写init、doFilter、destroy方法；
3. 在SpringBoot入口中添加注解@ServletComponentScan，以注册Filter；

注意：通过@Order注解设置过滤器的执行顺序，越小的越先被执行；

import org.springframework.core.annotation.Order;import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import java.io.IOException;/*** @ClassName: FilterDemo* @Author: 中都* @Date: 2021/12/29 22:11* @Description: 过滤器*/
@Order(1)
@WebFilter(filterName = "FilterDemo",urlPatterns = "/*")
public class FilterDemo implements Filter {@Overridepublic void init(FilterConfig filterConfig) throws ServletException {System.out.println("初始化逻辑，服务器启动时调用");}@Overridepublic void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {System.out.println("拦截器");filterChain.doFilter(servletRequest,servletResponse);}@Overridepublic void destroy() {System.out.println("销毁逻辑，服务器关闭时调用");}
}

@ServletComponentScan
@SpringBootApplication
public class SpringbootstudyApplication {public static void main(String[] args) {SpringApplication.run(SpringbootstudyApplication.class, args);}}

示例代码：

/*** @Author: zhondu* @Date: 2023/1/25 18:36* @Desc: 过滤器*/
@Component
public class LogFilter implements Filter {public static final Logger logger = LoggerFactory.getLogger(LogFilter.class);@Overridepublic void init(FilterConfig filterConfig) throws ServletException {}@Overridepublic void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {// filterChain是过滤器执行链，因为可以有多个过滤器的// 打印请求信息HttpServletRequest request = (HttpServletRequest) servletRequest;logger.info("-----------LogFilter 开始--------------");// 接口和方法类型（get post)logger.info("请求地址：{} {}", request.getRequestURL().toString(), request.getMethod());logger.info("远程地址：{}", request.getRemoteAddr());// 还可以打印其他很多信息，请求头之类的，因为这里拿到的是整个requestlong startTime = System.currentTimeMillis();filterChain.doFilter(servletRequest, servletResponse);logger.info("-----------LogFilter 结束  耗时：{} ms--------------", System.currentTimeMillis() - startTime);}
}

** 执行结果 **

2、监听器

监听对象的增删改查等操作，然后做出相应处理，用户统计在线人数、在线用户、系统加载时的信息初始化等等；

/*** @Author: zhondu* @Date: 2023/1/26 10:18* @Desc: 拦截器 Spring特有的，常用于登录校验 权限校验 请求日志打印*/
@Component
public class LogInterceptor implements HandlerInterceptor {public static final Logger logger = LoggerFactory.getLogger(LogInterceptor.class);/*** 拦截器 -- 请求进入方法之前的拦截处理* @param request* @param response* @param handler* @return* @throws Exception*/@Overridepublic boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {logger.info("-----------LogInterceptor 开始--------------");// 接口和方法类型（get post)logger.info("请求地址：{} {}", request.getRequestURL().toString(), request.getMethod());logger.info("远程地址：{}", request.getRemoteAddr());long startTime = System.currentTimeMillis();request.setAttribute("requestStartTime",startTime);// 返回true 才会继续走，否则就直接结束了，所以可以用于 登录校验 权限校验return true;}/*** 拦截器 -- 走完方法之后返回前端的拦截处理* @param request* @param response* @param handler* @param modelAndView* @throws Exception*/@Overridepublic void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {long startTime = (Long) request.getAttribute("requestStartTime");logger.info("-----------LogInterceptor 结束  耗时：{} ms--------------", System.currentTimeMillis() - startTime);}
}

拦截器还需要加一个全局配置的：

import com.zhondu.wiki.interceptor.LogInterceptor;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;import javax.annotation.Resource;/*** @Author: zhondu* @Date: 2023/1/26 10:26* @Desc:*/
@Configuration
public class SpringMvcConfig implements WebMvcConfigurer {@Resourceprivate LogInterceptor logInterceptor;@Overridepublic void addInterceptors(InterceptorRegistry registry) {// 增加过滤器 -- 针对所有的请求 （但是例如登录校验就不是所有的接口都需要校验，例如登录校验是不能校验登录接口本身的）registry.addInterceptor(logInterceptor).addPathPatterns("/**") // 针对所有的请求.excludePathPatterns("/login"); // 排除掉登录请求-不拦截}
}

拦截器分为前后两个方法，过滤器只有一个,而且过滤器是容器级别的（Tomcat netty等），拦截器是应用级别的，例如web应用

3、AOP

AOP也可以打印参数相关的信息，但是与过滤器拦截器不同，他依靠的不是request，而是连接点JoinPoint，

需要引入依赖：

        <!--AOP--><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-aop</artifactId></dependency><dependency><groupId>com.alibaba</groupId><artifactId>fastjson</artifactId><version>1.2.70</version></dependency>

package com.zhondu.wiki.aspect;import com.alibaba.fastjson.JSONObject;
import com.alibaba.fastjson.support.spring.PropertyPreFilters;
import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.Signature;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.aspectj.lang.annotation.Pointcut;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Component;
import org.springframework.web.context.request.RequestContextHolder;
import org.springframework.web.context.request.ServletRequestAttributes;
import org.springframework.web.multipart.MultipartFile;import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;/*** @Author: zhondu* @Date: 2023/1/26 11:49* @Desc: AOP*/
@Aspect
@Component
public class LogAspect {public static final Logger logger = LoggerFactory.getLogger(LogAspect.class);// 定义一个切点 监控所有的controller@Pointcut("execution(public * com.zhondu.*.controller..*Controller.*(..))")public void controllerPointcut() {}// 前置通知@Before("controllerPointcut()")public void doBefore(JoinPoint joinPoint) throws Throwable {// 开始打印请求日志ServletRequestAttributes attributes = (ServletRequestAttributes) RequestContextHolder.getRequestAttributes();HttpServletRequest request = attributes.getRequest();Signature signature = joinPoint.getSignature();String name = signature.getName();// 打印请求信息logger.info("------------- 开始 -------------");logger.info("请求地址: {} {}", request.getRequestURL().toString(), request.getMethod());logger.info("类名方法: {}.{}", signature.getDeclaringTypeName(), name);logger.info("远程地址: {}", request.getRemoteAddr());// 打印请求参数Object[] args = joinPoint.getArgs();// LOG.info("请求参数: {}", JSONObject.toJSONString(args));Object[] arguments  = new Object[args.length];for (int i = 0; i < args.length; i++) {if (args[i] instanceof ServletRequest|| args[i] instanceof ServletResponse|| args[i] instanceof MultipartFile) {continue;}arguments[i] = args[i];}// 排除字段，敏感字段或太长的字段不显示String[] excludeProperties = {"password", "file"};PropertyPreFilters filters = new PropertyPreFilters();PropertyPreFilters.MySimplePropertyPreFilter excludefilter = filters.addFilter();excludefilter.addExcludes(excludeProperties);logger.info("请求参数: {}", JSONObject.toJSONString(arguments, excludefilter));}/*** 环绕通知* @param proceedingJoinPoint* @return* @throws Throwable*/@Around("controllerPointcut()")public Object doAround(ProceedingJoinPoint proceedingJoinPoint) throws Throwable {long startTime = System.currentTimeMillis();Object result = proceedingJoinPoint.proceed();// 排除字段，敏感字段或太长的字段不显示String[] excludeProperties = {"password", "file"};PropertyPreFilters filters = new PropertyPreFilters();PropertyPreFilters.MySimplePropertyPreFilter excludefilter = filters.addFilter();excludefilter.addExcludes(excludeProperties);logger.info("返回结果: {}", JSONObject.toJSONString(result, excludefilter));logger.info("------------- 结束 耗时：{} ms -------------", System.currentTimeMillis() - startTime);return result;}
}

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