add_header

Adds the specified field to a response header provided that the response code equals 200, 201 (1.3.10), 204, 206, 301, 302, 303, 304,307 (1.1.16, 1.0.13), or 308 (1.13.0).Parameter value can contain variables.

There could be several add_header directives.These directives are inherited from the previous configuration level if and only if there are no add_header directivesdefined on the current level.

官方文档的意思也就是在响应状态码成功时，add_header指令才生效，并且当前“作用域”下没有 add_header指令时，会向上层继承。

  • 作用：使用add_header指令来设置response header
  • 官方示例
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Syntax: 	add_header name value [always];
Default: 	—
Context: 	http, server, location, if in location

#在不添加always的情况下，add_header只对响应码为200, 201 (1.3.10), 204, 206, 301, 302, 303, 304, 307 (1.1.16, 1.0.13), 308 (1.13.0)这些生效（括号内是nginx版本）。也就是说当服务端返回响应异常，响应码不是上述之一的话，即使nginx有配跨域头信息，浏览器仍然会显示跨域错误。原因就是因为nginx对异常响应码添加add_header无效
  • 示例
  1. 给根目录下添加header ，名字为name 值为tom
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location / {
    add_header name tom;
    root html;
    index index.html index.htm;
}

访问响应头部信息

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root@elk:/etc/nginx# curl -I -L localhost
HTTP/1.1 200 OK
Server: nginx/1.21.1
Date: Sat, 26 Mar 2022 15:20:27 GMT
Content-Type: text/html
Content-Length: 612
Last-Modified: Tue, 06 Jul 2021 14:59:17 GMT
Connection: keep-alive
ETag: "60e46fc5-264"
name: tom
Accept-Ranges: bytes
  1. 如果状态码不是200 204等测试是否生效
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location / {
    add_header name tom;
    root html;
    index index.html index.htm;
    return 510;
}

测试结果 没有添加等头部信息

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root@elk:/etc/nginx# curl -I -L localhost
HTTP/1.1 510
Server: nginx/1.21.1
Date: Sat, 26 Mar 2022 15:26:17 GMT
Content-Length: 0
Connection: keep-alive

3、添加always

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location / {
    add_header name tom always;
    root html;
    index index.html index.htm;
    return 510;
}

结果

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root@elk:/etc/nginx# curl -I -L localhost
HTTP/1.1 510
Server: nginx/1.21.1
Date: Sat, 26 Mar 2022 15:25:20 GMT
Content-Length: 0
Connection: keep-alive
name: tom

3.每一层都可以从上层继承 add_header，但是如果当前层添加了add_header，则不能继承

  1. http 模块
  2. server 模块
  3. location 模块
  4. location中的 if 模块
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server {
    listen 80;
    server_name localhost;

    #charset koi8-r;
    add_header name tom;

    #access_log  logs/host.access.log  main;

    location / {
        root html;
        index index.html index.htm;
    }
    location /a {
        add_header name tomcat;
        root html;
        index a.html;
    }
}

访问结果: 继承server 的add header

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root@elk:/var/log/nginx# curl -L -I localhost
HTTP/1.1 200 OK
Server: nginx/1.21.1
Date: Sat, 26 Mar 2022 15:34:47 GMT
Content-Type: text/html
Content-Length: 612
Last-Modified: Tue, 06 Jul 2021 14:59:17 GMT
Connection: keep-alive
ETag: "60e46fc5-264"
name: tom
Accept-Ranges: bytes

访问/a 目录 使用自己的 add header

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root@elk:/var/log/nginx# curl -L -I localhost/a
HTTP/1.1 301 Moved Permanently
Server: nginx/1.21.1
Date: Sat, 26 Mar 2022 15:35:49 GMT
Content-Type: text/html
Content-Length: 169
Location: http://localhost/a/
Connection: keep-alive
name: tomcat

HTTP/1.1 200 OK
Server: nginx/1.21.1
Date: Sat, 26 Mar 2022 15:35:49 GMT
Content-Type: text/html
Content-Length: 16
Last-Modified: Sat, 26 Mar 2022 15:29:01 GMT
Connection: keep-alive
ETag: "623f313d-10"
name: tomcat
Accept-Ranges: bytes