今天遇到一个很神奇的问题，之前写的项目，后端跨域都处理好的，按部就班使用原来的方式，前后端都开发完之后，部署本地后，跨域没起效，一脸懵逼，然后使用公司另外一个同事的跨域解决方案，具体我也没深入研究到底咋回事，先记录下来。

方式一

　　我之前的做法

CorsInterceptor.java

package net.ybclass.online_ybclass.interceptor;

import org.springframework.http.HttpMethod;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class CorsInterceptor implements HandlerInterceptor {
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        //表示接受任意域名的请求,也可以指定域名
        response.setHeader("Access-Control-Allow-Origin", request.getHeader("origin"));

        //该字段可选，是个布尔值，表示是否可以携带cookie
        response.setHeader("Access-Control-Allow-Credentials", "true");

        response.setHeader("Access-Control-Allow-Methods", "GET, HEAD, POST, PUT, PATCH, DELETE, OPTIONS");

        response.setHeader("Access-Control-Allow-Headers", "*");
        //这里可以不加，但是其他语言开发的话记得处理options请求
        /**
         * 非简单请求是对那种对服务器有特殊要求的请求，
         * 比如请求方式是PUT或者DELETE，或者Content-Type字段类型是application/json。
         * 都会在正式通信之前，增加一次HTTP请求，称之为预检。浏览器会先询问服务器，当前网页所在域名是否在服务器的许可名单之中，
         * 服务器允许之后，浏览器会发出正式的XMLHttpRequest请求
         */
        if (HttpMethod.OPTIONS.toString().equals(request.getMethod())) {
            return true;
        }
        return true;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {

    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {

    }
}

方式二

　　这是我同事的跨域解决方案

CorsFilter.java

package net.ybchen.demo;

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 javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.stereotype.Component;

@WebFilter(filterName="CorsFilter",urlPatterns= {"/*"})
@Component
public class CorsFilter implements Filter {

    final static org.slf4j.Logger logger = org.slf4j.LoggerFactory.getLogger(CorsFilter.class);

    @Override
    public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException {
        HttpServletResponse response = (HttpServletResponse) res;
        HttpServletRequest request = (HttpServletRequest) req;
        String url = request.getHeader("Origin");
        response.setHeader("Access-Control-Allow-Origin", url);
        response.setHeader("Access-Control-Allow-Methods", "POST, GET, OPTIONS, DELETE");
        response.setHeader("Access-Control-Allow-Credentials", "true");
        response.setHeader("Access-Control-Max-Age", "3600");
        response.setHeader("Access-Control-Allow-Headers", "x-requested-with,Accept,Origin,Content-Type,LastModified,Cookie,UTOKEN");
        String method = request.getMethod();
        if("OPTIONS".equals(method)){
            response.setStatus(200, "success");
            response.flushBuffer();
            return;
        }
        chain.doFilter(req, res);
    }
    @Override
    public void init(FilterConfig filterConfig) {}
    @Override
    public void destroy() {}
}

方式三

package net.ybchen.demo;

import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.web.servlet.FilterRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.transaction.annotation.EnableTransactionManagement;
import org.springframework.web.cors.CorsConfiguration;
import org.springframework.web.cors.UrlBasedCorsConfigurationSource;
import org.springframework.web.filter.CorsFilter;

@SpringBootApplication
@MapperScan("net.ybchen.demo.mapper")
@EnableTransactionManagement //开启事务
public class DemoApplication {

    public static void main(String[] args) {
        SpringApplication.run(DemoApplication.class, args);
    }

    @Bean
    public FilterRegistrationBean corsFilter() {
        UrlBasedCorsConfigurationSource source = new UrlBasedCorsConfigurationSource();
        CorsConfiguration config = new CorsConfiguration();
        config.setAllowCredentials(true);
        config.addAllowedOrigin("*");
        config.addAllowedHeader("*");
        config.addAllowedMethod("*");
        source.registerCorsConfiguration("/**", config);
        FilterRegistrationBean bean = new FilterRegistrationBean(new CorsFilter(source));
        bean.setOrder(0);
        return bean;
    }
}

方式四

package com.ybchen.config;

import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.CorsRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;

/**
 * @Description：跨域处理
 * @Author：chenyanbin
 * @Date：2021/3/16 下午2:12
 * @Versiion：1.0
 */
@Configuration
public class Cors extends WebMvcConfigurerAdapter {
    @Override
    public void addCorsMappings(CorsRegistry registry) {
        registry.addMapping("/**")
                .allowedOrigins("*")
                .allowedMethods("GET", "POST", "PUT", "OPTIONS", "DELETE", "PATCH")
                .allowCredentials(true)
                .maxAge(3600);
    }
}

方式五

    @Bean
    public FilterRegistrationBean filterRegistrationBean() {
        CorsConfiguration corsConfiguration = new CorsConfiguration();
        //1.允许任何来源
        corsConfiguration.setAllowedOriginPatterns(Collections.singletonList("*"));
        //2.允许任何请求头
        corsConfiguration.addAllowedHeader(CorsConfiguration.ALL);
        //3.允许任何方法
        corsConfiguration.addAllowedMethod(CorsConfiguration.ALL);
        //4.允许凭证
        corsConfiguration.setAllowCredentials(true);
        UrlBasedCorsConfigurationSource source = new UrlBasedCorsConfigurationSource();
        source.registerCorsConfiguration("/**", corsConfiguration);
        CorsFilter corsFilter = new CorsFilter(source);
        FilterRegistrationBean<CorsFilter> filterRegistrationBean=new FilterRegistrationBean<>(corsFilter);
        filterRegistrationBean.setOrder(-101);  // 小于 SpringSecurity Filter的 Order(-100) 即可
        return filterRegistrationBean;
    }