Re: [tcljava-user] How to use Interp.setResult?

[Mo D. <mo...@mo...>]

Bret Comstock Waldow wrote:
> Hello,
>
> I have not found good documentation for some of Jacl - the API docs on
> the tcljava.sourceforge.net site are not giving me a good enough
> understanding to determine how to solve an exception.
>
> I have a command-line java program.  In it's primary class constructor,
> it creates a TCL Interp session with the name of an external script
> file, and exits when the Interp session is complete.  In response to
> various commands found in a script, various Java objects are created,
> and methods called on those objects from the script.  I have a number of
> working examples of this, including some that successfully return values
> to the Interp session for further processing.
>
> But I haven't figured out what Interp.setResult() does, and it looks as
> if it might be useful.
The setResult() method sets the "result" pointer in a Jacl interpreter 
to a specific TclObject. It is typically
used from a Java implementation of a Tcl method to indicate the result 
of a Tcl command. If you have
a Java method, it is better to just have it return a Java result and 
then invoke the method with the java::call
command or from a class instance handle (like java0x1, a result object 
from a java::new command).
> TCL:
> $tableName getEntry $column $row
>
> Java:
>       /**
>        * *@return* int - The number of columns in this result set.
>        */
>       *public* *int* getColumnCount()
>             {
>             log.debug( "getColumnCount - columnCount is " + columnCount );
>             *return* columnCount;
>             }
>  
>       *public* *void* getEntry( String columnName, *int* currentRow )
> *throws* TclException
>             {
>             log.debug( "getEntry - column name is " + columnName );
>             myInterp.setResult( "an Answer" );
>             }
>  
>  
> tcl.lang.ReflectException
>             at tcl.lang.JavaInvoke.call(JavaInvoke.java:328)
>             at tcl.lang.JavaInvoke.callMethod(JavaInvoke.java:161)
>             at tcl.lang.ReflectObject.cmdProc(ReflectObject.java:916)
>   
It is not clear what if going on from this example code and stack trace. 
Typically, the ReflectException means there
was some error in the Java code and it got wrapped into a 
ReflectException when moving from Java back to tcl.

When Jacl hits a ReflectException, it saves the original Java exception 
object and a description string are saved
in the global variable named "errorCode". Printing out a stace trace of 
the Java exception found there would likely
be a good place to start.

Mo DeJong