面试被问跨域问题,怎么破?
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2022-08-25 18:34
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作者:酒香逢
来源:www.cnblogs.com/fnz0/p/15803011.html
当你遇到跨域问题,不要立刻就选择复制去尝试,请详细看完这篇文章再处理,我相信它能帮到你。
分析前准备:
前端网站地址:http://localhost:8080
服务端网址:http://localhost:59200
Access-Control-Allow-Origin 用于设置允许跨域请求源地址 (预检请求和正式请求在跨域时候都会验证) Access-Control-Allow-Headers 跨域允许携带的特殊头信息字段 (只在预检请求验证) Access-Control-Allow-Methods 跨域允许的请求方法或者说HTTP动词 (只在预检请求验证) Access-Control-Allow-Credentials 是否允许跨域使用cookies,如果要跨域使用cookies,可以添加上此请求响应头,值设为true(设置或者不设置,都不会影响请求发送,只会影响在跨域时候是否要携带cookies,但是如果设置,预检请求和正式请求都需要设置)。不过不建议跨域使用(项目中用到过,不过不稳定,有些浏览器带不过去),除非必要,因为有很多方案可以代替。
开始动手模拟:
server {
listen 22222;
server_name localhost;
location / {
proxy_pass http://localhost:59200;
}
}
情况1:
Access to XMLHttpRequest at 'http://localhost:22222/api/Login/TestGet' from origin 'http://localhost:8080' has been blocked by CORS policy: Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource.
server {
listen 22222;
server_name localhost;
location / {
add_header Access-Control-Allow-Origin 'http://localhost:8080';
proxy_pass http://localhost:59200;
}
}
server {
listen 22222;
server_name localhost;
location / {
add_header Access-Control-Allow-Origin 'http://localhost:8080' always;
proxy_pass http://localhost:59200;
}
}
情况2:
Access to XMLHttpRequest at 'http://localhost:22222/api/Login/TestGet' from origin 'http://localhost:8080' has been blocked by CORS policy: Response to preflight request doesn't pass access control check: It does not have HTTP ok status.
server {
listen 22222;
server_name localhost;
location / {
add_header Access-Control-Allow-Origin 'http://localhost:8080' always;
if ($request_method = 'OPTIONS') {
return 204;
}
proxy_pass http://localhost:59200;
}
}
情况3:
Access to XMLHttpRequest at 'http://localhost:22222/api/Login/TestGet' from origin 'http://localhost:8080' has been blocked by CORS policy: Request header field authorization is not allowed by Access-Control-Allow-Headers in preflight response.
server {
listen 22222;
server_name localhost;
location / {
add_header Access-Control-Allow-Origin 'http://localhost:8080' always;
if ($request_method = 'OPTIONS') {
add_header Access-Control-Allow-Headers 'authorization'; #为什么写在if里面而不是接着Access-Control-Allow-Origin往下写?因为这里只有预检请求才会检查
return 204;
}
proxy_pass http://localhost:59200;
}
}
There could be several add_header directives. These directives are inherited from the previous level if and only if there are no add_header directives defined on the current level.
意思就是当前层级无 add_header 指令时,则继承上一层级的add_header。相反的若当前层级有了add_header,就应该无法继承上一层的add_header。
server {
listen 22222;
server_name localhost;
location / {
add_header Access-Control-Allow-Origin 'http://localhost:8080' always;
if ($request_method = 'OPTIONS') {
add_header Access-Control-Allow-Origin 'http://localhost:8080';
add_header Access-Control-Allow-Headers 'authorization';
return 204;
}
proxy_pass http://localhost:59200;
}
}
server {
listen 22222;
server_name localhost;
location / {
if ($request_method = 'OPTIONS') {
add_header Access-Control-Allow-Origin 'http://localhost:8080';
add_header Access-Control-Allow-Headers 'authorization';
return 204;
}
if ($request_method != 'OPTIONS') {
add_header Access-Control-Allow-Origin 'http://localhost:8080' always;
}
proxy_pass http://localhost:59200;
}
}
情况4:
Access to XMLHttpRequest at 'http://localhost:22222/api/Login/TestGet' from origin 'http://localhost:8080' has been blocked by CORS policy: Method PUT is not allowed by Access-Control-Allow-Methods in preflight response.
server {
listen 22222;
server_name localhost;
location / {
if ($request_method = 'OPTIONS') {
add_header Access-Control-Allow-Origin 'http://localhost:8080';
add_header Access-Control-Allow-Headers 'content-type,authorization';
add_header Access-Control-Allow-Methods 'PUT';#为这么只加在这个if中,不再下面的if也加上?因为这里只有预检请求会校验,当然你加上也没事。
return 204;
}
if ($request_method != 'OPTIONS') {
add_header Access-Control-Allow-Origin 'http://localhost:8080' always;
}
proxy_pass http://localhost:59200;
}
}
情况5:
Access to XMLHttpRequest at 'http://localhost:22222/api/Login/TestGet' from origin 'http://localhost:8080' has been blocked by CORS policy: The 'Access-Control-Allow-Origin' header contains multiple values '*, http://localhost:8080', but only one is allowed.
↓ ↓ ↓ ↓ ↓
server {
listen 22222;
server_name localhost;
location / {
if ($request_method = 'OPTIONS') {
add_header Access-Control-Allow-Origin 'http://localhost:8080';
add_header Access-Control-Allow-Headers '*';
add_header Access-Control-Allow-Methods '*';
add_header Access-Control-Allow-Credentials 'true';
return 204;
}
if ($request_method != 'OPTIONS') {
add_header Access-Control-Allow-Origin 'http://localhost:8080' always;
add_header Access-Control-Allow-Credentials 'true';
}
proxy_pass http://localhost:59200;
}
}
或者:
server {
listen 22222;
server_name localhost;
location / {
add_header Access-Control-Allow-Origin 'http://localhost:8080' always;
add_header Access-Control-Allow-Headers '*';
add_header Access-Control-Allow-Methods '*';
add_header Access-Control-Allow-Credentials 'true';
if ($request_method = 'OPTIONS') {
return 204;
}
proxy_pass http://localhost:59200;
}
}