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18.6. Dead connections
The JDBC protocol does not provide a natural
connectionErrorOccured() event when a connection is broken. To support dead/broken connection checking there are a number of plug-ins.
18.6.1. Valid connection checking
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Valid connections can be checked with an SQL statement (as shown below) before handing the connection to the application.
<check-valid-connection-sql>select 1 from dual</check-valid-connection-sql>
If this fails, another connection is selected until there are no more connections at which point new connections are constructed.
A potentially more performant check is to use vendor specific features, for example Oracle or MySQL's
pingDatabase() tool:
<valid-connection-checker-class-name/>
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