http{

                略

     upstream tomcat_server {

        server 192.168.200.111:8080 weight=1; //指定Tomcat地址，weight值越高，负载越大

       #server 192.168.200.112:8080 weight=1;
       #server 192.168.200.113:8080 weight=1;  
     }

     server {

             略

         location / {

            root   html;

            index  index.html index.htm;

            proxy_pass http://tomcat_server;  //要与前面设置的名称相同
            proxy_set_header Host $http_host;  //重写请求头中的host字段，否则会报400错误

        }

     }

}