跨域访问支持（Spring Boot、Nginx、浏览器）

本文介绍: 我们的后端使用Spring Boot。Spring Boot跨域非常简单，只需书写以下代码即可。代码非常简单，不做赘述。该代码在Spring Boot 1.5.4中测试通过。

我们的后端使用Spring Boot。Spring Boot跨域非常简单，只需书写以下代码即可。

@Configuration
public class CustomCORSConfiguration {
  private CorsConfiguration buildConfig() {
    CorsConfiguration corsConfiguration = new CorsConfiguration();
    corsConfiguration.addAllowedOrigin("*");
    corsConfiguration.addAllowedHeader("*");
    corsConfiguration.addAllowedMethod("*");
    return corsConfiguration;
  }

  @Bean
  public CorsFilter corsFilter() {
    UrlBasedCorsConfigurationSource source = new UrlBasedCorsConfigurationSource();
    source.registerCorsConfiguration("/**", buildConfig());
    return new CorsFilter(source);
  }
}

代码非常简单，不做赘述。该代码在Spring Boot 1.5.4中测试通过。

某天，我们将Spring Boot应用用Nginx反向代理。而前端跨域请求的需求不减，于是乎。

Nginx跨域也比较简单，只需添加以下配置即可。

location / {
	proxy_pass http://localhost:8080;
	if ($request_method = 'OPTIONS') {
		add_header 'Access-Control-Allow-Origin' '*';
		add_header 'Access-Control-Allow-Methods' 'GET, POST, OPTIONS';
		add_header 'Access-Control-Allow-Headers' 'DNT,X-CustomHeader,Keep-Alive,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type,Content-Range,Range,Token';
		add_header 'Access-Control-Max-Age' 1728000;
		add_header 'Content-Type' 'text/plain; charset=utf-8';
		add_header 'Content-Length' 0;
		return 204;
	}
	if ($request_method = 'POST') {
		add_header 'Access-Control-Allow-Origin' '*';
		add_header 'Access-Control-Allow-Methods' 'GET, POST, OPTIONS';
		add_header 'Access-Control-Allow-Headers' 'DNT,X-CustomHeader,Keep-Alive,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type,Content-Range,Range,Token';
		add_header 'Access-Control-Expose-Headers' 'DNT,X-CustomHeader,Keep-Alive,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type,Content-Range,Range,Token';
	}
	if ($request_method = 'GET') {
		add_header 'Access-Control-Allow-Origin' '*';
		add_header 'Access-Control-Allow-Methods' 'GET, POST, OPTIONS';
		add_header 'Access-Control-Allow-Headers' 'DNT,X-CustomHeader,Keep-Alive,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type,Content-Range,Range,Token';
		add_header 'Access-Control-Expose-Headers' 'DNT,X-CustomHeader,Keep-Alive,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type,Content-Range,Range,Token';
	}
}

其中：add_header 'Access-Control-Expose-Headers' 务必加上你请求时所带的header。例如本例中的“Token”，其实是前端传给后端过来的。如果记不得也没有关系，浏览器的调试器会有详细说明。

参考文档：https://enable-cors.org/server_nginx.html