这里介绍两种几种种自定义filter的方式

• 通过@WebFilter+@ServletComponentScan的方式
• 通过配置FilterRegistrationBean的方式
• 通过加注解@component等注入的方式

1.通过@WebFilter+@ServletComponentScan的方式

filter类

package com.d4c.custombean.filter;

import lombok.extern.slf4j.Slf4j;
import org.springframework.core.annotation.Order;

import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import java.io.IOException;

@Slf4j
@Order(1)
@WebFilter(filterName = "firstName",urlPatterns = "/hello/*")
public class FirstFilter implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        log.info("FirstFilter init--------");
    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        log.info("FirstFilter doFilter--------");
        filterChain.doFilter(servletRequest,servletResponse);
    }

    @Override
    public void destroy() {
        log.info("FirstFilter destroy--------");
    }
}

启动类上要加@ServletComponentScan

package com.d4c.custombean;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.web.servlet.ServletComponentScan;

@ServletComponentScan
@SpringBootApplication
public class CustomBeanApplication {
    public static void main(String[] args) {
        SpringApplication.run(CustomBeanApplication.class, args);
    }
}

@WebFilter常用属性

属性	类型	是否必需	说明
asyncSupported	boolean	否	指定Filter是否支持异步模式
dispatcherTypes	DispatcherType[]	否	指定Filter对哪种方式的请求进行过滤。 支持的属性：ASYNC、ERROR、FORWARD、INCLUDE、REQUEST； 默认过滤所有方式的请求
filterName	String	否	Filter名称
initParams	WebInitParam[]	否	配置参数
displayName	String	否	Filter显示名
servletNames	String[]	否	指定对哪些Servlet进行过滤
urlPatterns/value	String[]	否	两个属性作用相同，指定拦截的路径

过滤器的urlPatterns的过滤路径规则：

• 1.全路径匹配： /hello/do.html
• 2.部分路径匹配： /hello/*
• 3.通配符匹配 ：/*
• 4.后缀名匹配 ：*.html(注意:前面不加/)

@Order
@Orde注解是决定着执行顺序，而不是类的初始化顺序。order数字越小，优先级越高。最好，统一用一种方式定义filter，否则@Order可能不起作用（混乱）。

2.通过配置FilterRegistrationBean的方式

filter类

package com.d4c.custombean.filter;

import lombok.extern.slf4j.Slf4j;

import javax.servlet.*;
import java.io.IOException;

@Slf4j
public class SecondFilter implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        log.info("SecondFilter init--------");
    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        log.info("SecondFilter doFilter--------");
        filterChain.doFilter(servletRequest,servletResponse);
    }

    @Override
    public void destroy() {
        log.info("SecondFilter destroy--------");
    }
}

配置类

package com.d4c.custombean.config;

import com.d4c.custombean.filter.SecondFilter;
import org.springframework.boot.web.servlet.FilterRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class MyRegisterBean {

    @Bean
    public FilterRegistrationBean filterRegistrationBean(){
        FilterRegistrationBean bean = new FilterRegistrationBean();
        //注册自定义过滤器
        bean.setFilter(new SecondFilter());
        //过滤器名称
        bean.setName("second filter bean");
        //过滤所有路径
        bean.addUrlPatterns("/do/*");
        //优先级，数字越小，优先级越高
        bean.setOrder(2);
        return bean;
    }
}

3.通过加注解@Component等注入的方式

虽然这种方式能实现filter，但是不推荐。最好第一种或第二种方式选其一

filter类

package com.d4c.custombean.filter;

import lombok.extern.slf4j.Slf4j;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;

import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import java.io.IOException;

@Slf4j
@Order(3)
//或者用@Configuration
@Component   
public class ThirdFilter implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        log.info("ThirdFilter init--------");
    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        log.info("ThirdFilter doFilter--------");
        filterChain.doFilter(servletRequest,servletResponse);
    }

    @Override
    public void destroy() {
        log.info("ThirdFilter destroy--------");
    }
}