B4J Question JBDC pool connections: how to use correctly ?

init mysql
2023-10-12 20:18:39.209:INFO :cmvci.AbstractPoolBackedDataSource:pool-1-thread-3: Initializing c3p0 pool... com.mchange.v2.c3p0.ComboPooledDataSource [ acquireIncrement -> 3, acquireRetryAttempts -> 30, acquireRetryDelay -> 1000, autoCommitOnClose -> false, automaticTestTable -> null, breakAfterAcquireFailure -> false, checkoutTimeout -> 20000, connectionCustomizerClassName -> null, connectionTesterClassName -> com.mchange.v2.c3p0.impl.DefaultConnectionTester, contextClassLoaderSource -> caller, dataSourceName -> 1hge15jaza6effljjbobg|6b1c0b35, debugUnreturnedConnectionStackTraces -> false, description -> null, driverClass -> com.mysql.jdbc.Driver, extensions -> {}, factoryClassLocation -> null, forceIgnoreUnresolvedTransactions -> false, forceSynchronousCheckins -> false, forceUseNamedDriverClass -> false, identityToken -> 1hge15jaza6effljjbobg|6b1c0b35, idleConnectionTestPeriod -> 600, initialPoolSize -> 3, jdbcUrl -> jdbc:mysql://localhost/stancontrol?characterEncoding=utf8&allowPublicKeyRetrieval=false&au
toReconnect=false&requireSSL=false&useSSL=false&pooling=true, maxAdministrativeTaskTime -> 0, maxConnectionAge -> 0, maxIdleTime -> 1800, maxIdleTimeExcessConnections -> 0, maxPoolSize -> 100, maxStatements -> 150, maxStatementsPerConnection -> 0, minPoolSize -> 3, numHelperThreads -> 3, preferredTestQuery -> null, privilegeSpawnedThreads -> false, properties -> {password=******, user=******}, propertyCycle -> 0, statementCacheNumDeferredCloseThreads -> 0, testConnectionOnCheckin -> false, testConnectionOnCheckout -> true, unreturnedConnectionTimeout -> 0, userOverrides -> {}, usesTraditionalReflectiveProxies -> false ]
main.main (java line: 28)
java.lang.RuntimeException: java.lang.RuntimeException: java.sql.SQLException: You can't operate on a closed Connection!!!
    at anywheresoftware.b4a.BA.raiseEvent2(BA.java:140)
    at anywheresoftware.b4a.BA.raiseEvent(BA.java:98)
    at peacemaker.sc4grabber.main.main(main.java:28)
Caused by: java.lang.RuntimeException: java.sql.SQLException: You can't operate on a closed Connection!!!
    at anywheresoftware.b4a.BA.raiseEvent2(BA.java:140)
    at anywheresoftware.b4a.objects.Timer$TickTack$1.run(Timer.java:135)
    at anywheresoftware.b4a.keywords.SimpleMessageLoop.runMessageLoop(SimpleMessageLoop.java:47)
    at anywheresoftware.b4a.StandardBA.startMessageLoop(StandardBA.java:43)
    at anywheresoftware.b4a.keywords.Common.StartMessageLoop(Common.java:180)
    at peacemaker.sc4grabber.main._appstart(main.java:157)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.D
elegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:566)
    at anywheresoftware.b4a.BA.raiseEvent2(BA.java:111)
    ... 2 more
Caused by: java.sql.SQLException: You can't operate on a closed Connection!!!
    at com.mchange.v2.sql.SqlUtils.toSQLException(SqlUtils.java:118)
    at com.mchange.v2.sql.SqlUtils.toSQLException(SqlUtils.java:77)
    at com.mchange.v2.c3p0.impl.NewProxyConnection.prepareStatement(NewProxyConnection.java:576)
    at anywheresoftware.b4j.objects.SQL.ExecQuery2(SQL.java:365)
    at anywheresoftware.b4j.objects.SQL.ExecQuery(SQL.java:353)
    at peacemaker.sc4grabber.main$ResumableSub_timSystem_Tick.resume(main.java:826)
    at peacemaker.sc4grabber.main._timsystem_tick(main.java:728)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke
(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:566)
    at anywheresoftware.b4a.BA.raiseEvent2(BA.java:111)
    ... 12 more
Caused by: java.lang.NullPointerException
    at com.mchange.v2.c3p0.impl.NewProxyConnection.prepareStatement(NewProxyConnection.java:540)
    ... 21 more

Sub timSystem_Tick
    timSystem.Enabled = False
    
    If machine_id = 0 Then
        Dim filter As Map: filter.Initialize
        filter.Put("scanner_name", others.Get_DeviceID)
        webapi1.API_LOAD("scanners", filter)
        Wait For API_LOADED (L As List)
        If L.Size > 0 Then
            Dim machine_id As Int = L.Get(0).As(Map).Get("machine_id")
            Log("machine_id = " & machine_id)
            timFTPupload_Tick
        Else
            Log("machine_id trouble !")
        End If   

    Else
        Dim names As ResultSet = db.SQL.ExecQuery("SELECT * FROM " & db.DBT_NAMES & " WHERE sent = '0' LIMIT 1")
        Do While names.NextRow
            Dim name As String = names.GetString("name")
            Log("Sending ... " & name)
            
' removed all
            
            Log("Sent: " & name)
            db.SQL.ExecNonQuery("UPDATE " & db.DBT_NAMES & " SET sent = '1' WHERE name = '" & name & "' LIMIT 1")    'sent status finally
        Loop
        names.Close
        names = Null
    End If

    timSystem.Enabled = True
End Sub

    Sub Process_Globals
    Dim SQL As SQL
    end sub
   
    Public Sub InitializeDB
    DBM.InitializeMySQL($"jdbc:mysql://${DBLocation}/${DBname}?characterEncoding=utf8&allowPublicKeyRetrieval=false&autoReconnect=false&requireSSL=false&useSSL=false&pooling=true"$, DBUsername, DBPassword, 100)
    SQL = DBM.GetSQL
    ...

SQL.Initialize2("com.mysql.jdbc.Driver", $"jdbc:mysql://${DBLocation}/${DBname}?characterEncoding=utf8&allowPublicKeyRetrieval=false&autoReconnect=false&requireSSL=false&useSSL=false&pooling=true"$, DBUsername, DBPassword)