Some daily questions about java, about the annotations of the framework (ssh)

what do these four annotations mean?
what does the second namespace / existence mean?
does the controller get context connection is equivalent to declaring that this class is a.
which boss can explain how to understand annotations in detail

?
Mar.11,2021
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-64f5-1eaf800-2264.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-1eaf800-2264.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
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