The error model

The Java error model is catch and throw. The LotusScript error model is the ON ERROR statement and the error handling block. LotusScript catches the Java error and maps it to its error processing model. This allows the LotusScript user to manipulate the Java error with LotusScript error semantics through the use of the JavaError class.

The user should look at the LotusScript Error before the JavaError properties. If an error is trapped within LotusScript before Java is called, JavaError.ErrorMsg and JavaError.StackTrace are empty strings. Note the following code:

Uselsx *javacon

Sub Initialize

Dim jSession As JavaSession

Dim cls As JavaClass

Dim obj As JavaObject

Dim msg As String

Dim jError As JavaError

On Error Goto ErrorHandling

Set jSession = New JavaSession()

Set cls = jSession.GetClass("java/lang/Short")

' This signature would not match any Constructor

Set obj = cls.CreateObject("(X)V", 1)

Print obj.toString()

Exit Sub

ErrorHandling:

Print Error ' "LS2J Error: Constructor failed to execute"

Set jError = jSession.getLastJavaError

Print "Java error: " jError.ErrorMsg ' empty String

Exit Sub

End Sub

The user attempts to call the java.lang.Short Constructor. The correct call is the signature for a short parameter:

Set obj = cls.CreateObject("(S)V", 1)

Instead the user calls the following:

Set obj = cls.CreateObject("(X)V", 1)

Since "X" doesn't match any Java type, LotusScript raises an error before calling Java. The only error message is in the LotusScript error:

LS2J Error: Constructor failed to execute

If the LotusScript portion of LS2J cannot detect an error, it calls Java. Suppose the code reads:

Set obj = cls.CreateObject("(I)V", 1)

This signature could match a Constructor with an int parameter. LotusScript detects no error; attempts to call the Java Constructor, and fails because the java.lang.Short class has no Constructor with an int parameter. The LotusScript Error is still:

LS2J Error: Constructor failed to execute

But because Java was called, there is also a jError.ErrorMsg:

java.lang.NoSuchMethodError: <init>

The JavaError object, when retrieved from the JavaSession, contains the last error and the last StackTrace.

Example code using JavaError

Sub Initialize

Dim mySession As New JavaSession

Dim myError As JavaError

On Error GoTo ErrorHandling

'...

' code here

'....

Exit Sub

ErrorHandling:

Set myError = mySession.getLastJavaError

print Error

print myError.ErrorMsg

print myError.StackTrace

End Sub

This code sample prints the LotusScript error, the Java error, and the Java StackTrace.

Examples of LotusScript errors that might be misunderstood

Example 1:

You try to instantiate an object, but you have the wrong signature or number of arguments.

LotusScript says:	LS2J: Null JavaObject
Java ErrorMsg says:	java.lang.NoSuchMethodError: <init>

Example 2:

You try to instantiate an object, but an error occurs in the Constructor.

LotusScript says:	LS2J: Null JavaObject
Java StackTrace says:	java.lang.ArrayIndexOutOfBoundsException at myGraph.<init>(Compiled Code)

Example 3a:

You try to execute a method, but use the wrong number of arguments.

LotusScript says:	LS2J: Parameter mismatch calling Method <Method Name here>
Java ErrorMsg says:	LS2J error

Example 3b:

Now, you execute the method with the right arguments but there is an error in the method.

LotusScript says:	LS2J: Parameter mismatch calling Method <Method Name here>
Java StackTrace says:	java.lang.ArrayIndexOutOfBoundsException: 3 at myGraph.setOrientation(myGraph.java:262)

Siehe auch

Using LS2J

Glossar