自定义过滤器通过request获取POST请求参数

场景：
自定义一个过滤器，过滤验证码是否填写（集成SpringSecurity）
前端：

<!--登录页面-->
<template>
    <div class="login-container">
        <el-form :model="loginForm" :rules="rules2"
                 status-icon
                 ref="loginForm"
                 label-position="left"
                 label-width="0px"
                 class="demo-ruleForm login-page">
            <h3 class="title">用户登录</h3>
            <el-form-item prop="username">
                <el-input type="text"
                          v-model="loginForm.username"
                          auto-complete="off"
                          placeholder="用户名"
                ></el-input>
            </el-form-item>
            <el-form-item prop="password">
                <el-input type="password"
                          v-model="loginForm.password"
                          auto-complete="off"
                          placeholder="密码"
                ></el-input>
            </el-form-item>
            <el-form-item prop="code">
                <el-input
                        v-model="loginForm.code"
                        auto-complete="off"
                        placeholder="验证码"
                        style="width: 63%"
                        @keyup.enter.native="handleLogin"
                >
                    <svg-icon slot="prefix" icon-class="validCode" class="el-input__icon input-icon" name = "yzm"/>
                </el-input>
                <div class="login-code">
                    <img :src="codeUrl" @click="getCode" class="login-code-img"/>
                </div>
            </el-form-item>
            <el-checkbox v-model="loginForm.rememberMe" style="margin:0px 0px 25px 0px;">记住密码</el-checkbox>
            <el-form-item style="width:100%;">
                <el-button
                        :loading="loading"
                        size="medium"
                        type="primary"
                        style="width:100%;"
                        @click.native.prevent="handleLogin"
                >
                    <span v-if="!loading">登 录</span>
                    <span v-else>登 录 中...</span>
                </el-button>
                <div style="float: right;">
                    <router-link class="link-type" :to="'/register'">立即注册</router-link>
                </div>
            </el-form-item>
        </el-form>
    </div>
</template>

<script>
    import ElPager from "element-ui/packages/pagination/src/pager";
    import { encrypt, decrypt } from '../utils/jsencrypt'
    import Cookies from "js-cookie";
    export default {
        components: {ElPager},
        data(){
            return {
                codeUrl: "",
                loginForm: {
                    username: 'admin',
                    password: '123',
                    rememberMe: false,
                    code: ""
                },
                rules2: {
                    username: [{required: true, message: '请输入用户名', trigger: 'blur'}],
                    password: [{required: true, message: '请输入密码', trigger: 'blur'}],
                    code: [{ required: true, message: "请输入验证码", trigger: "change" }]
                },
                loading: false,
                redirect: undefined
            }
        },
        //监听
        watch: {
            $route: {
                handler: function(route) {
                    this.redirect = route.query && route.query.redirect;
                },
                immediate: true
            }
        },
        created() {
            this.getCode();
            this.getCookie();
        },
        methods: {
            //获取验证码
            getCode(){
                this.$axios.get("http://localhost:8090/vercode").then(res=>{
                    this.codeUrl = "data:image/gif;base64," + res.data.img;
                }).catch(error=>{
                    console.log(error)
                })
            },
            //Cookie加密
            getCookie() {
                const username = Cookies.get("username");
                const password = Cookies.get("password");
                const rememberMe = Cookies.get('rememberMe');
                this.loginForm = {
                    username: username === undefined ? this.loginForm.username : username,
                    password: password === undefined ? this.loginForm.password : decrypt(password),
                    rememberMe: rememberMe === undefined ? false : Boolean(rememberMe)
                };
            },
            //点击登录
            handleLogin(){
                //表单验证
                this.$refs.loginForm.validate(valid => {
                    if(valid)
                    {
                        this.loading = true;
                        //如果开启了记住我功能，Cookie对密码加密
                        if (this.loginForm.rememberMe) {
                            Cookies.set("username", this.loginForm.username, { expires: 30 });
                            Cookies.set("password", encrypt(this.loginForm.password), { expires: 30 });
                            Cookies.set('rememberMe', this.loginForm.rememberMe, { expires: 30 });
                        } else {
                            Cookies.remove("username");
                            Cookies.remove("password");
                            Cookies.remove('rememberMe');
                        }
                        this.$axios.post("http://localhost:8090/doLogin", this.loginForm).then(res=>{
                            // 路由跳转指定页面
                            this.$router.push({ path: this.redirect || "/" }).catch(()=>{});
                            //登录成功
                            this.$message({
                                message: '恭喜你，登录成功',
                                type: 'success'
                            });
                        }).catch(error=>{
                            this.loading = false;
                            this.getCode();
                            this.$message.error(error.data);
                        })
                    }
                });
            },

        }
    };
</script>

<style scoped>
    .login-container {
        width: 100%;
        height: 100%;
    }
    .login-page {
        -webkit-border-radius: 5px;
        border-radius: 5px;
        margin: 180px auto;
        width: 350px;
        padding: 35px 35px 15px;
        background: #fff;
        border: 1px solid #eaeaea;
        box-shadow: 0 0 25px #cac6c6;
    }
    label.el-checkbox.rememberme {
        margin: 0px 0px 15px;
        text-align: left;
    }
</style>

后端：

package com.aoshen.common;

import com.alibaba.fastjson.JSON;
import com.alibaba.fastjson.JSONObject;
import com.aoshen.common.redis.RedisCache;
import com.aoshen.common.utils.StringUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.security.authentication.AuthenticationServiceException;
import org.springframework.stereotype.Component;
import org.springframework.web.filter.GenericFilterBean;

import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.nio.charset.StandardCharsets;

/**
 * @author aoshen
 * DATE 2021/12/6 15:22
 * 自定义过滤器：过滤验证码是否填写
 */
@Component
public class VerifyCodeFilter extends GenericFilterBean
{
    @Autowired
    private RedisCache redisCache;

    private String defaultFilterProcessUrl = "/doLogin"; //过滤访问的接口
    @Override
    public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException
    {
        HttpServletRequest request = (HttpServletRequest) req;
        HttpServletResponse response = (HttpServletResponse) res;
        if ("POST".equalsIgnoreCase(request.getMethod()) && defaultFilterProcessUrl.equals(request.getServletPath()))
        {
            // 从request中读取POST请求参数
            ServletInputStream inputStream = request.getInputStream();
            InputStreamReader reader = new InputStreamReader(inputStream, StandardCharsets.UTF_8);
            BufferedReader bfReader = new BufferedReader(reader);
            StringBuilder sb = new StringBuilder();
            String line;
            while ((line = bfReader.readLine()) != null){
                sb.append(line);
            }
            String str = sb.toString();
            JSONObject jsonObject = JSON.parseObject(str);
            String requestCaptcha = jsonObject.getString("code");
            //从redis中拿取
            String genCaptcha = redisCache.getCacheObject("vercode");
            if (StringUtils.isEmpty(requestCaptcha))
            {
                throw new AuthenticationServiceException("验证码不能为空!");
            }
            if (!genCaptcha.toLowerCase().equals(requestCaptcha.toLowerCase()))
            {
                throw new AuthenticationServiceException("验证码错误!");
            }
        }
        chain.doFilter(request, response);
    }
}