一：过滤器

1.过滤器介绍

过滤器是处于客户端与服务器资源文件之间的一道过滤网，帮助我们过滤一些不符合要求的请求。通常用作 Session校验，判断用户权限。

2.过滤器生命周期

使用过滤器很简单，只需要实现Filter类，然后重写它的3个方法即可。

• init方法：程序启动调用Filter的init()方法(永远只调用一次)；在容器中创建当前过滤器的时候自动调用这个方法。
• destory方法：程序停止调用Filter的destroy()方法(永远只调用一次)；在容器中销毁当前过滤器的时候自动调用这个方法。
• doFilter方法：doFilter()方法每次的访问请求如果符合拦截条件都会调用(程序第一次运行，会在servlet调用init()方法以后调用；不管第几次，都在调用doGet(),doPost()方法之前)。这个方法有3个参数，分别是ServletRequest、ServletResponse和FilterChain可以从参数中获取HttpServletReguest和HttpServletResponse对象进行相应的处理操作。

二：使用注解方式实现过滤器（@WebFilter） 

 1.在springboot 启动类添加该注解@ServletComponentScan

@SpringBootApplication@ServletComponentScan // 过滤器public class Springboot02WebTestApplication {    SpringApplication.run(Springboot02WebTestApplication.class, args);}

 2.写个过滤器类，实现Filter接口

import com.alibaba.fastjson.JSONObject;import org.springframework.core.annotation.Order;import javax.servlet.*;import javax.servlet.annotation.WebFilter;import javax.servlet.http.HttpServletRequest;import java.io.IOException;import java.io.PrintWriter;// urlPatterns 过滤路径  filterName 过滤器name@WebFilter(urlPatterns = "/user/*", filterName = "tokenFilter1")public class TokenFilter1 implements Filter {    @Override    public void init(FilterConfig filterConfig) throws ServletException {//        Filter.super.init(filterConfig);        System.out.println("init");    }    @Override    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {        System.out.println("doFilter");        HttpServletRequest request = (HttpServletRequest) servletRequest;        String token = request.getHeader("token");        System.out.println(token);        //该方法执行后直接运行至下一个过滤器        if(token!=null){            filterChain.doFilter(servletRequest, servletResponse);        }else{            servletResponse.setCharacterEncoding("UTF-8");            servletResponse.setContentType("application/json; charset=utf-8");            PrintWriter out = servletResponse.getWriter();            JSONObject res = new JSONObject();            res.put("msg", "错误");            res.put("success", "false");            out.append(res.toString());        }    }    @Override    public void destroy() {//        Filter.super.destroy();        System.out.println("destroy");    }}

3.访问，我使用的Postman软件进行的测试

        添加请求头token信息，才可以访问成功。

三：使用非注解方式实现过滤器（直接注入到spring中）

 1.Filter代码

import com.alibaba.fastjson.JSONObject;import javax.servlet.*;import javax.servlet.http.HttpServletRequest;import java.io.IOException;import java.io.PrintWriter;public class TokenFilter2 implements Filter {    @Override    public void init(FilterConfig filterConfig) throws ServletException {        System.out.println("init");    }    @Override    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {        System.out.println("doFilter");        HttpServletRequest request = (HttpServletRequest) servletRequest;        String token = request.getHeader("token");        System.out.println(token);        //该方法执行后直接运行至下一个过滤器        if(token!=null){            filterChain.doFilter(servletRequest, servletResponse);        }else{            servletResponse.setCharacterEncoding("UTF-8");            servletResponse.setContentType("application/json; charset=utf-8");            PrintWriter out = servletResponse.getWriter();            JSONObject res = new JSONObject();            res.put("msg", "错误");            res.put("success", "false");            out.append(res.toString());        }    }    @Override    public void destroy() {        System.out.println("destroy");    }}

 2.Filter配置文件

import com.itsufu.filter.TokenFilter2;import org.springframework.boot.web.servlet.FilterRegistrationBean;import org.springframework.context.annotation.Bean;import org.springframework.context.annotation.Configuration;@Configurationpublic class FilterConfig {    // Filter代码类    @Bean    public TokenFilter2 tokenFilter2() {        return new TokenFilter2();    }    @Bean    public FilterRegistrationBean getFilterRegistrationBean(TokenFilter2 tokenFilter2) {        FilterRegistrationBean filterRegistrationBean = new FilterRegistrationBean();        filterRegistrationBean.setFilter(tokenFilter2);        filterRegistrationBean.setOrder(2);        filterRegistrationBean.addUrlPatterns("/user/*");        filterRegistrationBean.setName("tokenFilter2");        return filterRegistrationBean;    }}

 3.测试与注解式一样。

在此，祝各位帅哥美女，步步高升，一帆风顺！！！

来源地址：https://blog.csdn.net/Microhoo_/article/details/129968379