1 服务端全开的配置

@Configuration




    

public class WebConfig implements WebMvcConfigurer {
    @Override
    public void addCorsMappings(CorsRegistry registry) {
        registry.addMapping("/**")
                .allowedOrigins("*")
                //.allowedMethods("POST", "GET", "PUT", "OPTIONS", "DELETE")
                .allowedMethods("*")
                .allowedHeaders("*")
                .exposedHeaders("*")
                .maxAge(3600)
                //.exposedHeaders(RedisConstant.TOKEN_HEADER)
               .allowCredentials(true);
1.1 效果描述
1.1.1 服务端allowCredentials=true时
服务端必须返回特定的Access-Control-Allow-Headers和Access-Control-Allow-Origin,
不能是星号,否则会被浏览器拦截,认为跨域失败
1.1.1.2 此时预检请求时,服务端返回:
  Access-Control-Allow-Credentials: true
  Access-Control-Allow-Headers: app-version, content-type, device-id, device-type, version-code
  Access-Control-Allow-Methods: POST
  Access-Control-Allow-Origin: http://localhost:60664
  Access-Control-Max-Age: 3600
  Allow: GET, HEAD, POST, PUT, DELETE, OPTIONS, PATCH
  Connection: keep-alive
  Content-Length: 0
  Date: Tue, 11 Oct 2022 10:47:45 GMT
  Keep-Alive: timeout=60
  Vary: Origin
  Vary: Access-Control-Request-Method
  Vary: Access-Control-Request-Headers
预检请求后的正常请求里, 服务端返回:
  Access-Control-Allow-Credentials: true
  Access-Control-Allow-Origin: http://localhost:60664
  Connection: keep-alive
  Content-Type: application/json
  Date: Tue, 11 Oct 2022 10:47:47 GMT
  Keep-Alive: timeout=60
  Transfer-Encoding: chunked
  Vary: Origin
  Vary: Access-Control-Request-Method
  Vary: Access-Control-Request-Headers
1.1.2 如果服务端配置 .allowCredentials(false),那么响应头:
        Access-Control-Allow-Headers: app-version, content-type, device-id, device-type, version-code
        Access-Control-Allow-Methods: POST
        Access-Control-Allow-Origin: *
        Access-Control-Max-Age: 3600
        Allow: GET, HEAD, POST, PUT, DELETE, OPTIONS, PATCH
        Connection: keep-alive
        Content-Length: 0
        Date: Tue, 11 Oct 2022 10:50:48 GMT
        Keep-Alive: timeout=60
        Vary: Origin
        Vary: Access-Control-Request-Method
        Vary: Access-Control-Request-Headers
此时,此时后台还是可以set-cookie,但web端无法在下次请求携带
此时,如果web端代码设置了Credentials=true,那么这个响应会被浏览器拦截掉,cors失败
此时,如果web端设置withCredentials为false,则可以请求,但不携带cookie. 下次正常请求时,后端的响应头为:
 Access-Control-Allow-Origin: *
 Connection: keep-alive
 Content-Type: application/json
 Date: Tue, 11 Oct 2022 10:55:15 GMT
 Keep-Alive: timeout=60
 Transfer-Encoding: chunked
 Vary: Origin
 Vary: Access-Control-Request-Method
 Vary: Access-Control-Request-Headers
2 代理服务器的处置
本质上就是修改预检请求和正常请求的响应头,欺骗浏览器.
反向代理: nginx
开发时localhost的正向代理: nodejs,或者dart的shelf-proxy
写法应该参照上面贴出的抓包的响应头来处理,而不是全部设置为*
spring boot cros配置里全部设置为*时,spring 有进行针对性处理. 那么我们自己编写修改响应头代码时,也要遵守对应的规范:
对shelf-proxy的改写:
修改的完全版本.
代码库为: web_dev_proxy_shelf
// 修改响应头
  //有时后台写了Access-Control-Allow-Origin,那么server.defaultResponseHeaders的设置就会无效
  //if("OPTIONS" == (clientResponse?.request?.method??"")){
  Map<String, String> headers = clientResponse.headers;
  //不能同时多个
  headers.remove('access-control-allow-origin');
  headers.remove('access-control-allow-methods');
  headers.remove('access-control-allow-headers');
  headers.remove('access-control-expose-headers');
  headers.remove('access-control-max-age');
  headers.remove('access-control-allow-credentials');
  //你请求什么,就允许什么
  //access-control-request-headers 这个是chrome加了,所以在request!.headers里取不到
  //Request header field app-version is not allowed by Access-Control-Allow-Headers in preflight response.
  //Map<String, String> reqeustHeaders = clientResponse!.request!.headers!;
  String headerStr = clientResponse!.request!
      .headers['access-control-request-headers'].toString();
  //预检请求不会携带额外的header,所以下面拼接header没有鸟用, 要用access-control-request-headers取
  //reqeustHeaders.forEach((key, value) { headerStr = headerStr+","+key; });
  //access-control-request-headers
  if (headerStr == "null") {
    headerStr = "*";
  clientResponse.headers['Access-Control-Allow-Headers'] = headerStr;
  //clientResponse.headers['Access-Control-Allow-Headers'] = "*";//预检请求里,['Access-Control-Allow-Credentials'] = 'true'时 不能用*
  clientResponse.headers['Access-Control-Allow-Methods'] = "*";  //GET,POST,PUT,OPTIONS
  clientResponse.headers['Access-Control-Expose-Headers'] = headerStr;
  clientResponse.headers['Access-Control-Max-Age'] = '36000'; //如果chrome开启了禁用缓存,那么每次都会发预检请求
  clientResponse.headers['Access-Control-Allow-Credentials'] = 'true';
  //预检请求: 设置了-Allow-Credentials'] = 'true'时,两个限制:
  // Access-Control-Allow-Origin'] 不能为 "*"  -Allow-Headers'] = "*"
  //clientResponse.headers['Access-Control-Allow-Origin'] = "*";
  String original = clientResponse!.request!.headers["Referer"].toString();
  if(original == "null"){
    original = "*";
  if (original.endsWith("/")) {
    original = original.substring(0, original.length - 1);
  clientResponse.headers['Access-Control-Allow-Origin'] = original;
  //The value of the 'Access-Control-Allow-Origin' header in the response must not be the wildcard '*' when the request's credentials mode is 'include'.
  // The credentials mode of requests initiated by the XMLHttpRequest is controlled by the withCredentials attribute.
ngnix的配置
一般测试环境正式环境部署时,都是关掉spring boot里的cors配置,使用nginx重写响应头. 逻辑和上面的shelf-proxy的逻辑一致.
如果项目需要使用cookie(web项目一般都需要)
网上一搜,多数跨域配置都用不了,都写的什么玩意.
这一篇比较靠谱: 014.Nginx跨域配置
location /pub/(.+) {
    if ($http_origin ~ <允许的域（正则匹配）>) {
        add_header 'Access-Control-Allow-Origin' "$http_origin";
        add_header 'Access-Control-Allow-Credentials' "true";
        if ($request_method = "OPTIONS") {
            add_header 'Access-Control-Max-Age' 86400;
            add_header 'Access-Control-Allow-Methods' 'GET, POST,PUT, OPTIONS, DELETE';
            add_header 'Access-Control-Allow-Headers' 'reqid, nid, host, x-real-ip, x-forwarded-ip, event-type, event-id, accept, content-type';
            # 线上推荐写死特定的header,测试环境可以使用 $http_access_control_request_headers, 表示你请求什么我允许什么
            add_header 'Content-Length' 0;
            add_header 'Content-Type' 'text/plain, charset=utf-8';
            return 204;
    # 正常nginx配置
    ......
注意:注意:注意:
上面是add_header,要生效就要把web服务器内部自己的cors配置关掉,否则出现多个响应头. 导致跨域失败.
如果被代理的服务器是别人的,有部分这些响应头,则会造成跨域失败. 此时,应该去直接修改响应头.
修改响应头可参考:
nginx替换响应头（重点：如何在替换时加上if判断）
如果项目不需要使用cookie
在上面基础上修改.
  add_header 'Access-Control-Allow-Credentials' "true";
此时可以设置*了:
 add_header 'Access-Control-Allow-Origin' *
二 cookie的跨域
修改响应头里的set-cookie
将cookie的samesite设置为None,此时Secure也要设置为true.
域名一般设置为二级域名,比较通用
开发时,一般是本地代理服务器直接改:
void transferCookies(http.StreamedResponse clientResponse,String localHost) {
  String? cookie = clientResponse.headers['set-cookie'];
  if (cookie == null || cookie.isEmpty) {
    return;
//服务器要发送多个 cookie，则应该在同一响应中发送多个 Set-Cookie 标头。
  Cookie cookie2 = Cookie.fromSetCookieValue(cookie);
  cookie2.secure = true;
  cookie2.httpOnly = false;
  cookie2.domain = localHost;
  clientResponse.headers['set-cookie'] = cookie2.toString() + ";SameSite=None;";
  print("reset set-cookie header from $cookie to \n ${clientResponse.headers['set-cookie']}\n");
上线时,一般是应用服务器写cookie时配置好
比如普通返回时:
  StpUtil.logout();
        //将cookie里原token置为空:
        ResponseCookie cookie2 = ResponseCookie.from("navi-token","") // key & value
                .httpOnly(false)      // 禁止js读取
                .secure(true)     // 在http下也传输
//                    .domain("localhost")// 域名
                .path("/")       // path
                .maxAge(10L)   // 有效期10s
                .sameSite("None")  // 大多数情况也是不发送第三方 Cookie，但是导航到目标网址的 Get 请求除外
                .build();
        response.setHeader(HttpHeaders.SET_COOKIE, cookie2.toString());
又比如sa-token里配置:
// 获取配置Bean (以代码的方式配置Sa-Token, 此配置会覆盖yml中的配置)
@Bean
@Primary
public SaTokenConfig getSaTokenConfigPrimary() {
    SaTokenConfig config = new SaTokenConfig();
    config.setTokenName("navi-token");             // token名称 (同时也是cookie名称)
    //config.setTimeout(30 * 24 * 60 * 60);       // token有效期，单位s 默认30天
    config.setActivityTimeout(-1);              // token临时有效期 (指定时间内无操作就视为token过期) 单位: 秒
    config.setIsConcurrent(false);               // 是否允许同一账号并发登录 (为true时允许一起登录, 为false时新登录挤掉旧登录)
    config.setIsShare(false);                    // 在多人登录同一账号时，是否共用一个token (为true时所有登录共用一个token, 为false时每次登录新建一个token)
    config.setTokenStyle("uuid");               // token风格
    config.setIsLog(true);// 是否输出操作日志
    SaCookieConfig cookieConfig = new SaCookieConfig();
    cookieConfig.setSameSite("None");
    cookieConfig.setSecure(true);
    //cookieConfig.setHttpOnly(true);
    cookieConfig.setDomain(".xxxxx.tech");
    config.setCookie(cookieConfig);
    return config;
       
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