SpringBoot注册Filter的两种实现方式

springboot版本：2.2.5

一、filter注册

springboot中添加filter有两种方式：

1、实现方法一

package com.example.demo.filter1;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

import org.springframework.stereotype.Component;

/**
* Springboot实现filter的方式一：
* 实现Filter接口，并使用@Component注解
* 需要注意的是：这个方式注册的filter的执行顺序优先级较低
* @author Administrator
*
*/
@Component
public class FilterSample1 implements Filter {

@Override
 public void init(FilterConfig filterConfig) throws ServletException {
   System.out.println("这里是"+this.getClass().getName()+"的init");

}

@Override
 public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
     throws IOException, ServletException {
   System.out.println("这里是"+this.getClass().getName()+"的doFilter");
   chain.doFilter(request,response);
 }

@Override
 public void destroy() {
   System.out.println("这里是"+this.getClass().getName()+"的doFilter");

}
}

2、实现方法二

package com.example.demo.filter2;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

public class FilterSample2 implements Filter{

@Override
 public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
     throws IOException, ServletException {
   System.out.println("这里是"+this.getClass().getName()+"的doFilter");
   chain.doFilter(request,response);

}
}

package com.example.demo.filter2;

import java.util.ArrayList;

import org.springframework.boot.web.servlet.FilterRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

/**
* Springboot注册filter方法二：
* 同样要实现filter接口，但filter注册使用@Bean的方式进行注册，可以设置filter顺序
* @author Administrator
*
*/
@Configuration
public class WebConfig {
 @Bean
 public FilterRegistrationBean<FilterSample2> filterSample2() {
   FilterRegistrationBean<FilterSample2> registrationBean = new FilterRegistrationBean<FilterSample2>();
   FilterSample2 myFilter = new FilterSample2();
   registrationBean.setFilter(myFilter);
   ArrayList<String> urls = new ArrayList<>();
   urls.add("/*");//配置过滤规则
   registrationBean.setUrlPatterns(urls);
   registrationBean.setOrder(3);
   return registrationBean;
 }
}

二、Springboot自带filter

Springboot默认启用了三个filter，他们是requestContextFilter，characterEncodingFilter，formContentFilter，可以通过在application.yml中设置debug: true来验证如下：

2020-03-17 22:13:17.254 DEBUG 2700 --- [           main] o.s.b.w.s.f.OrderedRequestContextFilter  : Filter 'requestContextFilter' configured for use
2020-03-17 22:13:17.255 DEBUG 2700 --- [           main] s.b.w.s.f.OrderedCharacterEncodingFilter : Filter 'characterEncodingFilter' configured for use
2020-03-17 22:13:17.255 DEBUG 2700 --- [           main] o.s.b.w.s.f.OrderedFormContentFilter     : Filter 'formContentFilter' configured for use

三、查看应用中注册了哪些filter

#application.yml
debug: true

如上图，启用debug模式，查看日志可得：

标蓝部分详细内容如下：

2020-03-17 22:13:17.244 DEBUG 2700 --- [           main] o.s.b.w.s.ServletContextInitializerBeans :
Mapping filters:
filterRegistrationBean urls=[/*] order=3,
characterEncodingFilter urls=[/*] order=-2147483648,
formContentFilter urls=[/*] order=-9900,
requestContextFilter urls=[/*] order=-105,
filterSample1 urls=[/*] order=2147483647

可以看出，该应用注册了五个filter，执行顺序由order决定

来源：https://segmentfault.com/a/1190000023501017