springboot版本：2.2.5
一、filter註冊
springboot中添加filter有兩種方式：
1、實現方法一

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實現filter的方式一：
• 實現Filter接口，並使用@Component註解
• 需要注意的是：這個方式註冊的filter的執行順序優先級較低
• @author Administrator
  *

*/
@Component
public class FilterSample1 implements Filter {

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

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

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

}

2、實現方法二
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("這裡是"+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註冊filter方法二：
• 同樣要實現filter接口，但filter註冊使用@Bean的方式進行註冊，可以設置filter順序
• @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("/*");//配置過濾規則
    registrationBean.setUrlPatterns(urls);
    registrationBean.setOrder(3);
    return registrationBean;
}

}

二、Springboot自帶filter
Springboot默認啟用了三個filter，他們是requestContextFilter，characterEncodingFilter，formContentFilter，可以通過在application.yml中設置debug: true來驗證如下：
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、查看應用中註冊了哪些filter

application.yml

debug: true

如上圖，啟用debug模式，查看日誌可得：

標藍部分詳細內容如下：

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，該應用註冊了五個filter，執行順序由order決定