spring boot 过滤器_拦截器和过滤器的区别面试

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发布于 2022-09-23 11:22:34

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发布于 2022-09-23 11:22:34

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原文地址：https://www.tsanyang.top/share-detail/836252049946443776.html

最近实现一个权限控制功能，想通过拦截器进行实现，当业务一切按预期一样完成，有一个特别控制需要再拦截器对参数进行解析使用，但是发现当我们再拦截器读取了输入流，再控制器是无法获取到参数的，这个是由于输入流只能被读取一次，然后通过问题搜索了一把，看见网上通过重写HttpServletRequestWrapper实现输入流读取后，再写入回去，这样解决控制器无法获取参数问题，故在此做记录。

过滤器与拦截器到底有啥区别呢？一、实现原理不同

过滤器的实现基于回调函数

拦截器基于Java的反射机制【动态代理】实现。

二、使用范围不同

过滤器是Servlet的规范，需要实现javax.servlet.Filter接口，Filter使用需要依赖于Tomcat等容器。

拦截器是Spring组件，定义在org.springframework.web.servlet包下，由Spring容器管理，不依赖Tomcat等容器。

在Spring Boot中使用过滤器一、自定义过滤器

package com.example.filterinterceptor.filter;

import com.example.filterinterceptor.config.TsanHttpServletRequestWrapper;

import javax.servlet.*; import javax.servlet.http.HttpServletRequest; import java.io.BufferedReader; import java.io.IOException; import java.util.Date;

/**

@Author: tsanyang

@ClassName: TsanFilter

@Description: 实现filter过滤器

@Date: 2021/4/25 22:07

@Version v1.0

修改人—修改日期—修改内容 */ public class TsanFilter implements Filter { @Override public void init(FilterConfig filterConfig) throws ServletException {

}

@Override public void destroy() {

}

@Override public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException { // 执行前开始时间 long start = new Date().getTime(); ServletRequest requestWrapper = null; if (servletRequest instanceof HttpServletRequest) { requestWrapper = new TsanHttpServletRequestWrapper((HttpServletRequest) servletRequest); } if (requestWrapper == null) { filterChain.doFilter(servletRequest, servletResponse); } else { // 使用包装类让输入流可重复读取（） HttpServletRequest httpServletRequest = (HttpServletRequest) requestWrapper; String token = httpServletRequest.getHeader(“token”); // String a = getPostData(httpServletRequest); // Map<String, String[]> map = request.getParameterMap(); // 读取流。注：只能读取一次 // String str = getPostData(request); filterChain.doFilter(requestWrapper, servletResponse); } // 输出执行用了多少时间 System.out.print((new Date()).getTime() – start); }

private String getPostData(HttpServletRequest req) throws IOException { BufferedReader bufferReaderBody = null; try {

     bufferReaderBody = new BufferedReader(req.getReader());
     String postData = bufferReaderBody.readLine();
     return postData;
 } catch (IOException e) {
     throw e;
 } finally {
     if (bufferReaderBody != null) {
         bufferReaderBody.close();
     }
 }

} } 二、配置过滤器

package com.example.filterinterceptor.config;

import com.example.filterinterceptor.filter.TsanFilter; import org.springframework.boot.web.servlet.FilterRegistrationBean; import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.Configuration;

/**

@Author: tsanyang
@ClassName: WebConfig
@Description: Servlet过滤器配置文件
@Date: 2021/4/25 22:15
@Version v1.0
修改人—修改日期—修改内容 */ @Configuration public class WebFilterConfig { @Bean public FilterRegistrationBean tsanRegistrationBean() { FilterRegistrationBean filterRegistrationBean = new FilterRegistrationBean(); filterRegistrationBean.setFilter(new TsanFilter()); filterRegistrationBean.addUrlPatterns(“/filter”,”/postFilter”,”/postFilterFile”); return filterRegistrationBean; }

} 在Spring Boot中使用拦截器一、自定义拦截器

package com.example.filterinterceptor.interceptor;

import org.springframework.web.servlet.HandlerInterceptor; import org.springframework.web.servlet.ModelAndView;

import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.util.Date;

/**

@Author: tsanyang
@ClassName: TsanInterceptor
@Description: 自定义拦截器
@Date: 2021/4/25 22:40
@Version v1.0
修改人—修改日期—修改内容 */ public class TsanInterceptor implements HandlerInterceptor { // 保障变量线程安全 ThreadLocal start = new ThreadLocal<>(); @Override public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception { start.set(new Date().getTime()); return true; } @Override public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception { System.out.print((new Date().getTime() – start.get())); } @Override public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception { } } 二、配置拦截器

package com.example.filterinterceptor.config;

import com.example.filterinterceptor.interceptor.TsanInterceptor; import org.springframework.context.annotation.Configuration; import org.springframework.web.servlet.config.annotation.InterceptorRegistry; import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

/**

@Author: tsanyang
@ClassName: InterceptorConfig
@Description: 拦截器配置文件
@Date: 2021/4/25 22:51
@Version v1.0
修改人—修改日期—修改内容 */ @Configuration public class InterceptorConfig implements WebMvcConfigurer { @Override public void addInterceptors(InterceptorRegistry registry) { registry.addInterceptor(new TsanInterceptor()).addPathPatterns(“/interceptor”); } } 三、过滤器和拦截器使用测试接口

package com.example.filterinterceptor.controller;

import org.springframework.web.bind.annotation.*; import org.springframework.web.multipart.MultipartFile;

import java.io.IOException; import java.io.InputStream; import java.util.Map; import java.util.concurrent.TimeUnit;

/**

@Author: tsanyang
@ClassName: TsanController
@Description: 测试拦截器和过滤器
@Date: 2021/4/25 22:12
@Version v1.0
修改人—修改日期—修改内容 */ @RestController public class TsanController { @GetMapping(“/filter”) public String getFilterHello(@RequestParam String param) throws InterruptedException { // 休眠1分钟 TimeUnit.MINUTES.sleep(1); return param; } @PostMapping(“/postFilterStr”) public String postFilterStr(String str) { return str; } @PostMapping(“/postFilterMap”) public Map<String, String> postFilterMap(@RequestBody Map<String, String> map) { return map; } @PostMapping(“/postFilterFile”) public void postFilterMap(@RequestParam(“file”) MultipartFile multipartFile) throws IOException { String fileName = multipartFile.getName(); InputStream inputStream = multipartFile.getInputStream(); } @GetMapping(“/interceptor”) public String getInterceptorHello() throws InterruptedException { // 休眠5秒钟 TimeUnit.SECONDS.sleep(5); return “Interceptor Hello”; }

} 四、处理输入流可重复读取

package com.example.filterinterceptor.config;

import org.springframework.util.StreamUtils;

import javax.servlet.ReadListener; import javax.servlet.ServletInputStream; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletRequestWrapper; import java.io.BufferedReader; import java.io.ByteArrayInputStream; import java.io.IOException; import java.io.InputStreamReader;

/**

@Author: tsanyang

@ClassName: TsanHttpServletRequestWrapper

@Description: 读取流后包装

@Date: 2021/4/25 22:58

@Version v1.0

修改人—修改日期—修改内容 */ public class TsanHttpServletRequestWrapper extends HttpServletRequestWrapper { // 用于将流保存下来 private byte[] requestBody = null;

public TsanHttpServletRequestWrapper(HttpServletRequest request) throws IOException { super(request); requestBody = StreamUtils.copyToByteArray(request.getInputStream());

}

@Override public ServletInputStream getInputStream() throws IOException {

 final ByteArrayInputStream bais = new ByteArrayInputStream(requestBody);

 return new ServletInputStream() {

     @Override
     public int read() throws IOException {
         return bais.read();
     }

     @Override
     public boolean isFinished() {
         return false;
     }

     @Override
     public boolean isReady() {
         return false;
     }

     @Override
     public void setReadListener(ReadListener readListener) {

     }
 };

}

@Override public BufferedReader getReader() throws IOException{ return new BufferedReader(new InputStreamReader(getInputStream())); } }

总结

原理实现上：过滤器基于回调实现，而拦截器基于动态代理；

控制粒度上：过滤器和拦截器都能够实现对请求的拦截功能，但是在拦截的粒度上有较大的差异，拦截器对访问控制的粒度更细；

使用场景上：拦截器往往用于权限检查、日志记录等，过滤器主要用于过滤请求中无效参数，安全校验；

依赖容器上：过滤器依赖于Servlet容器，局限于web，而拦截器依赖于Spring框架，能够使用Spring框架的资源，不仅限于web；

触发时机上：过滤器在Servlet前后执行，拦截器在handler前后执行，现在大多数web应用基于Spring，拦截器更细；

流重复读取：通过重写HttpServletRequestWrapper实现，此方法不能用在文件上传上，文件上传实现思路先保存至本地，在将文件路径写入请求属性中，然后再业务中通过请求属性获取文件。

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