B4J Question NullPointerException MQTT error in DEBUG mode [solved]

[jmon]

Hello

Since yesterday I started having some errors that I've never seen, and can't find where the problem is. The error seems to be cause by MQTT, when I receive a message from clients.

This is the error:

...
# Connected: true
Error occurred on line: 65
java.lang.NullPointerException
    at anywheresoftware.b4a.shell.Shell.setStateBeforeUserSub(Shell.java:387)
    at anywheresoftware.b4a.shell.Shell.raiseEventImpl(Shell.java:288)
    at anywheresoftware.b4a.shell.Shell.raiseEvent(Shell.java:159)
    at sun.reflect.GeneratedMethodAccessor63.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at anywheresoftware.b4a.BA.raiseEvent2(BA.java:79)
    at anywheresoftware.b4a.ShellBA.raiseEvent2(ShellBA.java:92)
    at anywheresoftware.b4a.BA$3.run(BA.java:219)
    at com.sun.javafx.application.PlatformImpl.lambda$null$173(PlatformImpl.java:295)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.application.PlatformImpl.lambda$runLater$174(PlatformImpl.java:294)
    at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
    at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at com.sun.glass.ui.win.WinApplication.lambda$null$148(WinApplication.java:191)
    at java.lang.Thread.run(Thread.java:745)
Error occurred on line: 65
java.lang.NullPointerException
    at anywheresoftware.b4a.shell.Shell.runGoodChain(Shell.java:358)
    at anywheresoftware.b4a.shell.Shell.raiseEventImpl(Shell.java:169)
    at anywheresoftware.b4a.shell.Shell.raiseEvent(Shell.java:159)
    at sun.reflect.GeneratedMethodAccessor63.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at anywheresoftware.b4a.BA.raiseEvent2(BA.java:79)
    at anywheresoftware.b4a.ShellBA.raiseEvent2(ShellBA.java:92)
    at anywheresoftware.b4a.BA$3.run(BA.java:219)
    at com.sun.javafx.application.PlatformImpl.lambda$null$173(PlatformImpl.java:295)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.application.PlatformImpl.lambda$runLater$174(PlatformImpl.java:294)
    at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
    at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at com.sun.glass.ui.win.WinApplication.lambda$null$148(WinApplication.java:191)
    at java.lang.Thread.run(Thread.java:745)

This is my line 65, it's actually the first line of a sub:

(65) Sub Client_MessageArrived (Topic As String, Payload() As Byte)
    ....

My app is both a Broker (jMQTTBroker) and a Client. I think this error is raised when the broker-client sends a message to everyone, including itself. When other clients send a message to my broker I don't get an error.

What is strange is that this error happens in debug mode several times in a row, but then when I switch to release, the error is gone.

Also strange is that I never seen any error like this until yesterday, but I didn't change that part of the code yesterday...

Any idea?

Thank you for your help.

[EDIT]
it happens with any client, not only when the broker sends itself a message

[EDIT]
seems to happen only in debug mode, works in release

 

[jmon]

after testing more, it seems to be caused by this sub (in the master broker-client app):

Sub Client_Connected (Success As Boolean)
    Log($"# Connected: ${Success}"$)
    If Success Then
        'Success, then connect to the topic:
        Client.Subscribe("master/#", QOS)
        Send("clients/whosConnected", "")
    Else
        TimerConnect.Enabled = True
    End If
End Sub

This is when my broker-client is connected to the broker (itself). After being connected, the broker-client sends a message to the "clients/" to ask who is connected. The clients reply with a simple message so that this broker-client can build a list of clients.

the error happens when a client replies to that Send("clients/whosConnected", "") message and the sub "Client_MessageArrived" is raised in the broker-client app.

this is how the clients reply:

Sub Client_MessageArrived (Topic As String, Payload() As Byte)
    Dim msg As Message = serializator.ConvertBytesToObject(Payload)
        Select Topic
            Case "clients/whosConnected"
                Send("master/connected", "")
'....
End Sub

Sub Send(Topic As String, Payload As Object)
    If Client.Connected Then
        Client.Publish2(Topic, serializator.ConvertObjectToBytes(CreateMessage(Payload)), 0, False)
    Else
        Log($"Error sending message: NOT CONNECTED"$)
    End If
End Sub

Sub CreateMessage(Payload As Object) As Message
    Dim msg As Message
    msg.Initialize
    msg.Payload = Payload
    msg.FromClient = Main.CLIENT_ME
    msg.Id = Misc.GenerateUniqueId
    msg.TimestampSent = DateTime.Now
    Return msg
End Sub

 

[EnriqueGonzalez]

Hi!!

I had a not so related error, may be it is completly different, for you to judge.

Recently i released an app that communicates via HTTP, but for whatever reason, after some time it just fails with the following error showing on CMD

main._appstart (java line: 65)

java.lang.RuntimeException: java.io.FileNotFoundException: C:\Users\Raul\AppData

\Local\Temp\16 (Acceso denegado)

  at anywheresoftware.b4a.BA.raiseEvent2(BA.java:108)

  at anywheresoftware.b4a.BA$3.run(BA.java:219)

  at anywheresoftware.b4a.keywords.SimpleMessageLoop.runMessageLoop(Simple

MessageLoop.java:30)

The problem is that StartMessageLoop is called once, but it does not happen when it is called but after some time (a timer is running in background and i am sure this timer is never calling StartMessageLoop)

But the most strange is that I do not have any call to a file.

well...EVEN STRANGER is that the error happens when i make an HTTP call, but the log (that is just after the sub) is never reached.

Sub JobDone (Job As HttpJob)
    Log("JobName = " & Job.JobName & ", Success = " & Job.Success)

To partially solve the issue i changed:

Sub Application_Error (Error As Exception, StackTrace As String) As Boolean
    LogError(StackTrace)
    Return False ' was true
End Sub

 

[Erel]

This is a debugger issue.

Is it easy to reproduce with your project? Can you send me your project?

 

[jmon]

Is it easy to reproduce with your project? Can you send me your project?

Thank you for your help. I'll see if that can be reproduced with a smaller project and send it to you.

 

[jmon]

I sent the project to Erel, he found the problem, and this will be fixed in B4J v5.50.

Thank you for your help