- The database service is not running or has been stopped.
- The credentials (username and password) for the database login are incorrect.
- The database connection URL is incorrect.
- The database server firewall is blocking the connection.
- The database server has exceeded the maximum connection limit.
- The database server lacks resources, such as insufficient memory and disk space.
- There is an error in the database configuration, such as misconfiguring the database port number.
- The JDBC driver version is not compatible with the database version.
- Issues with internet connection, such as instability and delays.
- The database has reached the maximum connection limit.
- The improper configuration of the database connection pool leads to either premature or delayed release of connections.
- The JDBC driver file is missing or damaged.
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