An attempt by a client to checkout a Connection have timed out.

caused by:java.sql.SQLException:An attempt by a client to checkout a Connection have timed out.
At Com.mchange.v2.sql.SqlUtils.toSQLException (sqlutils.java:106)
At Com.mchange.v2.sql.SqlUtils.toSQLException (sqlutils.java:65)
At Com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutPooledConnection (c3p0pooledconnectionpool.java:527 )
At Com.mchange.v2.c3p0.impl.AbstractPoolBackedDataSource.getConnection (abstractpoolbackeddatasource.java:128)
At Org.springframework.jdbc.datasource.DataSourceUtils.doGetConnection (datasourceutils.java:113)
At Org.springframework.jdbc.datasource.DataSourceUtils.getConnection (datasourceutils.java:79)
... 5 more
caused by:com.mchange.v2.resourcepool.timeoutexception:a client timed out whilst waiting to acquire A resource from COM.M Change.v2.resourcepool.basicresourcepool@2020851–timeout at Awaitavailable ()
At Com.mchange.v2.resourcepool.BasicResourcePool.awaitAvailable (basicresourcepool.java:1317)
At Com.mchange.v2.resourcepool.BasicResourcePool.prelimCheckoutResource (basicresourcepool.java:557)
At Com.mchange.v2.resourcepool.BasicResourcePool.checkoutResource (basicresourcepool.java:477)
At Com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutPooledConnection (c3p0pooledconnectionpool.java:525 )
... 8 more

Using the C3P0 link pool when reported errors, check that the concurrency is too large when the time will occur, the solution is to change the property in the configuration file name= "Acquireincrement" value= "5", when the link is exhausted c3p0 one-time access to the number of connections. If not configured, the default is 3