The project is deployed in tomcat.

nginx configuration:

server {
        listen       8083 ;
        server_name  域名;

        location / {

            index  index.html index.htm index.jsp;
            #proxy_redirect off;
            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_pass http://127.0.0.1:8081/;
        }                       
}

It cannot be accessed directly through the domain name. After adding the 8081 port, you can access it smoothly. The direct IP port method is also available.

After just changing the domain name behind server_name to localhost, and restarting nginx, the direct domain name can be accessed, but after more than ten minutes it fails again, and I still need to add a port. Strange.