SpringBoot中如何实现注册Filter的两种不同方法？

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Spring Boot版本：2.2.5+

一、Filter注册

在Spring Boot中添加Filter有两种方式：

1.实现Filter接口

javapackage com.example.demo.filter1;

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 CustomFilter implements Filter { @Override public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException { // Filter逻辑 chain.doFilter(request, response); }}

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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