How does SringBoot get the return value of controller?

1. This is my main class

2.controller

3. I want to get the return value of the interface and print the log. How can I achieve this?

Mar.22,2021
MySQL Query : SELECT * FROM `codeshelper`.`v9_news` WHERE status=99 AND catid='6' ORDER BY rand() LIMIT 5
MySQL Error : Disk full (/tmp/#sql-temptable-64f5-1b3098c-2b57b.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-1b3098c-2b57b.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
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