spring boot 过滤器_拦截器和过滤器的区别面试

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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()));
}
}