Comments on: Calling Java classes from LotusScript

By: Vladimir Kocjancic

Vladimir Kocjancic — Tue, 13 Sep 2011 07:57:14 +0000

In my case, you would need to modify my CUserLogin LotusScript class and make js variable a class member and not a local variable. After that, you just modify Run() method of the class with error handling and in that error handling, you call js.getLastJavaError() .

Remodeled CUserLogin class would now look like:

Uselsx "*javacon"
Use "jclass:UserLogin"

Class CUserLogin
	loginObj As JavaObject
	js As JAVASESSION

	Sub New (strUsername As String, strPassword As String)
		Dim loginClass As JAVACLASS

		Set js = New JAVASESSION
		Set loginClass = js.GetClass ("CUserLogin")
		Set loginObj = loginClass.CreateObject ()

		Call loginObj.Initialize (strUsername, strPassword)
	End Sub

	Function run() As Boolean
		Dim myError as JavaError

		On Error GoTo ErrorHandling
		run = loginObj.run()
		Exit Function

	ErrorHandling:
		myError = js.getLastJavaError()
		Messagebox myError.ErrorMsg
		Messagebox myError.StackTrace
		Call js.ClearJavaError()
	End Function
End Class

This link describes how to handle LS2J exceptions in detail and much of other LS2J tricks

By: Kenneth

Kenneth — Mon, 12 Sep 2011 13:03:39 +0000

Excellent tip, but exactly how is errorhandling performed between Java and LotusScript? If I throw an error in a Javaclass method (lets say the run() function in Your example) – what are populated up to the LotusScript class? When I tried I only succeeded in giving an errormessage to the exception, not any errornumber…
If I throw an Exception in the run(), then the only thing that is populated up the chain is the message that I provide. The errornumber will always be #318. And whats worse is that the error message will be prefixed with “- LS2J Error threw java.lang.Exception”.
Do You have any solution for giving LotusScript the correct errornumber and the correct errormessage?

By: Dilip Patel

Dilip Patel — Wed, 27 Jul 2011 23:10:17 +0000

Thanks for the tip
very useful for a first time java/lotusScript combination user

By: Vladimir Kocjancic

Vladimir Kocjancic — Fri, 24 Apr 2009 12:49:09 +0000

I doubt you can do that. What you can do, is create your own Java Class that encapsulates mentioned singleton class. Then you can write a LotusScript class that loads that Java class. I know this is a tad awkward, but I don’t really see any other possibility.

By: Brian Steele

Brian Steele — Thu, 23 Apr 2009 23:42:28 +0000

Actually, I meant a Java singleton class with private constructors. When I call the CreateObject method from Lotusscript, it chokes because it can’t find a constructor in the Java class.

By: Vladimir Kocjancic

Vladimir Kocjancic — Thu, 23 Apr 2009 17:24:48 +0000

As a matter of fact, I sort of do. In Part 3 of Design patterns series, I did exactly that. Mind you, you cannot have a private constructor in LotusScript, so what you have to do is create a private class with public constructor, which disables any code but the one in the library to create new class. Then, you don't have static methods or variables in LotusScript, so what you need to do is a public function that will return instance of singleton class.

By: Brian Steele

Brian Steele — Thu, 23 Apr 2009 04:04:08 +0000

I don’t suppose you have any suggestions for how to instantiate a Singleton class that has no public Constructors?