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