SpringBoot之过滤器

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#过滤器 #springboo filter #filter

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本文围绕过滤器展开，介绍其可在前端拦截用户请求，应用于web资源管理、权限控制等。阐述了自定义Filter的实现方式，包括@WebFilter和FilterRegistrationBean，还说明了自定义步骤。通过新建MyFilter、配置类和Controller进行实践，并测试了过滤器优先级，总结出Order值低的优先执行。

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过滤器

过滤器可以在前端拦截所有用户的请求。

过滤器的应用

对web服务器所有资源的管理
对url级别的权限进行控制
过滤数据
记录日志

自定义Filter的实现方式

@WebFilter 不能设置过滤器的优先级
FilterRegistrationBean

自定义Filter步骤

实现Filter接口
添加@Configuration注解，将自定义的Filter加入过滤器链

新建MyFilter

package com.chen.springbootfilter.filter;

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

public class MyFilter implements Filter {

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        HttpServletRequest request = (HttpServletRequest) servletRequest;
        System.out.println("this is MyFilter,url :"+request.getRequestURI());
        filterChain.doFilter(servletRequest,servletResponse);
    }

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        System.out.println("===init===");
    }

    @Override
    public void destroy() {
        System.out.println("===destroy===");
    }
}

新建配置类

package com.chen.springbootfilter.config;

import com.chen.springbootfilter.filter.MyFilter;
import org.springframework.boot.web.servlet.FilterRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class WebConfiguration {

    @Bean
    public FilterRegistrationBean testFilterRegistration(){
        FilterRegistrationBean registration = new FilterRegistrationBean();
        registration.setFilter(new MyFilter());
        registration.addUrlPatterns("/*");
        registration.setName("MyFilter");
        registration.setOrder(10);
        return registration;
    }
}

新建Controller

package com.chen.springbootfilter.controller;

import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class HelloController {

    @RequestMapping("/hello")
    public String index(){
        return "hello";
    }
}

代码结构

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运行结果

在这里插入图片描述

优先级测试

新建MyFilter2，代码和MyFilter一致。
在配置类中设置优先级。

package com.chen.springbootfilter.filter;

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

public class MyFilter2 implements Filter {

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        HttpServletRequest request = (HttpServletRequest) servletRequest;
        System.out.println("this is MyFilter 2,url :"+request.getRequestURI());
        filterChain.doFilter(servletRequest,servletResponse);
    }

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        System.out.println("===init===");
    }

    @Override
    public void destroy() {
        System.out.println("===destroy===");
    }
}

package com.chen.springbootfilter.config;

import com.chen.springbootfilter.filter.MyFilter;
import com.chen.springbootfilter.filter.MyFilter2;
import org.springframework.boot.web.servlet.FilterRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class WebConfiguration {

    @Bean
    public FilterRegistrationBean testFilterRegistration() {
        FilterRegistrationBean registration = new FilterRegistrationBean();
        registration.setFilter(new MyFilter());
        registration.addUrlPatterns("/*");
        registration.setName("MyFilter");
        registration.setOrder(10);
        return registration;
    }

    @Bean
    public FilterRegistrationBean test2FilterRegistration() {
        FilterRegistrationBean registration = new FilterRegistrationBean();
        registration.setFilter(new MyFilter2());
        registration.addUrlPatterns("/*");
        registration.setName("MyFilter2");
        registration.setOrder(1);
        return registration;
    }

}

在这里插入图片描述
总结：过滤器器 MyFilter 2 因为 Order 值设置得低，会优先被执⾏。