Nginx domain name configuration for react and spring boot application

http {

 # React App configuration
  server {
    listen 80;
    server_name domain_name www.domain_name;
    location / {
        proxy_pass http://127.0.0.1:3000;
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Proto $scheme;
        proxy_cache_bypass $http_upgrade;
        proxy_redirect off;
     }
  }

# Spring boot configuration
 server{
    listen 80;
    server_name subdomain_name www.subdomain_name;
    location / {
        proxy_pass http://127.0.0.1:8000;
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Proto $scheme;
        proxy_cache_bypass $http_upgrade;
        proxy_redirect off;

     }
  }
}

Make sure your react app and spring application is up and running