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

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