HikariCP接続プールがJavaで機能しているかどうかを確認する方法は？

まず、maximum

hibernate.hikari.maximumPoolSize=10
hibernate.hikari.minimumIdle=10

プールが機能している場合は、ポート3306（または以下の例ではmssql 1433）への10個のESTABLISHED接続が表示されます。

lsof -nP -i :1433 -sTCP:ESTABLISHED
COMMAND  PID       USER   FD   TYPE  DEVICE SIZE/OFF NODE NAME
java    1596 lmc  260u  IPv6 1624799      0t0  TCP 127.0.0.1:43022->127.0.0.1:1433 (ESTABLISHED)
java    1596 lmc  265u  IPv6 1626072      0t0  TCP 127.0.0.1:43026->127.0.0.1:1433 (ESTABLISHED)
java    1596 lmc  266u  IPv6 1630933      0t0  TCP 127.0.0.1:43030->127.0.0.1:1433 (ESTABLISHED)
java    1596 lmc  267u  IPv6 1631705      0t0  TCP 127.0.0.1:43034->127.0.0.1:1433 (ESTABLISHED)
java    1596 lmc  268u  IPv6 1632268      0t0  TCP 127.0.0.1:43038->127.0.0.1:1433 (ESTABLISHED)
java    1596 lmc  269u  IPv6 1632273      0t0  TCP 127.0.0.1:43042->127.0.0.1:1433 (ESTABLISHED)
java    1596 lmc  270u  IPv6 1632278      0t0  TCP 127.0.0.1:43046->127.0.0.1:1433 (ESTABLISHED)

ssを使用する （ソケット統計）

ss -46 -np state established dport = :1433 | grep 'java' | sort -r -k 3,3 | nl
     1  tcp    0       0          [::ffff:127.0.0.1]:43158     [::ffff:127.0.0.1]:1433   users:(("java",pid=1596,fd=273))                                               
     2  tcp    0       0          [::ffff:127.0.0.1]:43154     [::ffff:127.0.0.1]:1433   users:(("java",pid=1596,fd=272))                                               
     3  tcp    0       0          [::ffff:127.0.0.1]:43150     [::ffff:127.0.0.1]:1433   users:(("java",pid=1596,fd=271))                                               
     4  tcp    0       0          [::ffff:127.0.0.1]:43142     [::ffff:127.0.0.1]:1433   users:(("java",pid=1596,fd=270))                                               
     5  tcp    0       0          [::ffff:127.0.0.1]:43138     [::ffff:127.0.0.1]:1433   users:(("java",pid=1596,fd=269))                                               
     6  tcp    0       0          [::ffff:127.0.0.1]:43134     [::ffff:127.0.0.1]:1433   users:(("java",pid=1596,fd=268))                                               
     7  tcp    0       0          [::ffff:127.0.0.1]:43130     [::ffff:127.0.0.1]:1433   users:(("java",pid=1596,fd=267))                                               
     8  tcp    0       0          [::ffff:127.0.0.1]:43126     [::ffff:127.0.0.1]:1433   users:(("java",pid=1596,fd=266))                                               
     9  tcp    0       0          [::ffff:127.0.0.1]:43122     [::ffff:127.0.0.1]:1433   users:(("java",pid=1596,fd=265))                                               
    10  tcp    0       0          [::ffff:127.0.0.1]:43118     [::ffff:127.0.0.1]:1433   users:(("java",pid=1596,fd=260))

netstatを使用する （ssを優先して一部のディストリビューションでは非推奨 ）

netstat -ant | grep 3306
tcp        0      0 127.0.0.1:41722     127.0.0.1:3306      ESTABLISHED 
tcp        0      0 127.0.0.1:41730     127.0.0.1:3306      ESTABLISHED 
tcp        0      0 127.0.0.1:41728     127.0.0.1:3306      ESTABLISHED 
tcp        0      0 127.0.0.1:41726     127.0.0.1:3306      ESTABLISHED 
tcp        0      0 127.0.0.1:41716     127.0.0.1:3306      ESTABLISHED 
tcp        0      0 127.0.0.1:41732     127.0.0.1:3306      ESTABLISHED 
tcp        0      0 127.0.0.1:41720     127.0.0.1:3306      ESTABLISHED 
tcp        0      0 127.0.0.1:41736     127.0.0.1:3306      ESTABLISHED 
tcp        0      0 127.0.0.1:41718     127.0.0.1:3306      ESTABLISHED 
tcp        0      0 127.0.0.1:41724     127.0.0.1:3306      ESTABLISHED