drjava-hackers

[DrJava] BeanShell

[Peter C. <cen...@ri...>]

I just took another look at BeanShell, a java-like scripting 
environment very similar to DynamicJava.  The website is here:

<http://www.beanshell.org/>

BeanShell has recently added a few features which would be of interest 
to us for DrJava.  In particular, there is a new "Strict Java" mode, 
which forces all variable declarations to be typed and all script 
statements to have Java-legal syntax.  If I remember correctly, this 
feature has already been requested for consistency reasons for teaching 
in DrJava.  In normal mode, BeanShell will use DJ-style loose typing, 
as well as automatic boxing and unboxing of primitives and an enhanced 
print (i.e. System.out) mechanism.

Another feature that would be handy for newbies is a "global import" 
statement: "import *" which maps out the entire classpath.  Ambiguities 
in naming caused by the global import will be reported at runtime and 
can be corrected with (an) additional import statement(s).  This is 
coupled with a "which" command that prints the exact filesystem 
location of any known Java identifier.  Considering the amount of 
difficulty that new students have in understanding the classpath rules, 
this could be extremely helpful.

BeanShell already ships with a Swing-based console which integrates via 
I/O Streams or a custom interface, complete with history completion.  
We could also use a lower level of integration with the engine if we 
chose, a la DynamicJava.  Everything is LGPL, so we'd have full access 
to the code and it would be compatible with our license.

The last advantage would be consistency with other similar tools.  The 
Emacs JDE already integrates with BeanShell, and Sun is planning to use 
it in a future version of Forte and the NetBeans IDE.  As far as I can 
tell, DynamicJava is a strict subset of BeanShell, so there's little 
reason to hold out with an unpopular technology.

Obviously this would take a significant amount of work, but I think it 
would be a worthwhile venture.  What opinions are there from the other 
developers?

--
Peter

Re: [DrJava] BeanShell

[Brian S. <bs...@bs...>]

On BeanShell: The first prototype of an interpreter-based REPL for 
DrJava that I did was actually based on BeanShell. I switched to 
DynamicJava for reasons I don't remember at the moment -- it might have 
been language feature support they had at the time, perhaps lacking 
anonymous inner classes or something. Or it may have been an ease of 
integration issue, or even licensing at that time (I think they used to 
have a different license).

Anyway, BeanShell is certainly a more living project than DynamicJava 
and it sounds like it has improved some since I last checked it out. It 
sounds like not a bad idea to move to it, although the range of 
improvements sound like it wouldn't be worth your effort to spend too 
much time on it.

On the other hand, it shouldn't be too hard to implement. The REPL was 
designed from the beginning to allow swapping out the interpeter. Pretty 
much, you should be able to implement model.repl.JavaInterpreter and 
swap that in instead. (I think there is a bit of DynamicJava-specific 
code in other places, like handling the returned values/error messages, 
but it shouldn't be hard to clean up.)

One small concern to point out: Seems like they blew it with regard to 
returning the "no result" value, like DynamicJava did (before I fixed it 
in our subclass). From their docs:

If an evaluation of a statement or expression yields a "void" value; 
such as would be the case for something like a for-loop or a void type 
method invocation, eval() returns null.

This same problem in DynamicJava was the reason, if you left off the 
semicolon, you used to get "null" as the result for void-returning 
statements.

Anyhow, just wanted to throw in my few cents.

-brian

Re: [DrJava] BeanShell

[Eric A. <eri...@ma...>]

One thing to keep in mind: we should soon be extending the interpreter 
to handle NextGen-style generics. That will entail (1) 
mangling/demangling of type identifiers, and (2) a modified class 
loader. We need to assess how easy both of these things will be with 
BeanShell vs. DynamicJava. I'd expect it shouldn't be very hard in 
either case, but we need to keep it in mind.

-- Eric


On Sunday, November 3, 2002, at 02:46 PM, Peter Centgraf wrote:

> I just took another look at BeanShell, a java-like scripting 
> environment very similar to DynamicJava.  The website is here:
>
> <http://www.beanshell.org/>
>
> BeanShell has recently added a few features which would be of interest 
> to us for DrJava.  In particular, there is a new "Strict Java" mode, 
> which forces all variable declarations to be typed and all script 
> statements to have Java-legal syntax.  If I remember correctly, this 
> feature has already been requested for consistency reasons for 
> teaching in DrJava.  In normal mode, BeanShell will use DJ-style loose 
> typing, as well as automatic boxing and unboxing of primitives and an 
> enhanced print (i.e. System.out) mechanism.
>
> Another feature that would be handy for newbies is a "global import" 
> statement: "import *" which maps out the entire classpath.  
> Ambiguities in naming caused by the global import will be reported at 
> runtime and can be corrected with (an) additional import statement(s). 
>  This is coupled with a "which" command that prints the exact 
> filesystem location of any known Java identifier.  Considering the 
> amount of difficulty that new students have in understanding the 
> classpath rules, this could be extremely helpful.
>
> BeanShell already ships with a Swing-based console which integrates 
> via I/O Streams or a custom interface, complete with history 
> completion.  We could also use a lower level of integration with the 
> engine if we chose, a la DynamicJava.  Everything is LGPL, so we'd 
> have full access to the code and it would be compatible with our 
> license.
>
> The last advantage would be consistency with other similar tools.  The 
> Emacs JDE already integrates with BeanShell, and Sun is planning to 
> use it in a future version of Forte and the NetBeans IDE.  As far as I 
> can tell, DynamicJava is a strict subset of BeanShell, so there's 
> little reason to hold out with an unpopular technology.
>
> Obviously this would take a significant amount of work, but I think it 
> would be a worthwhile venture.  What opinions are there from the other 
> developers?
>
> --
> Peter
>
>
>
> -------------------------------------------------------
> This SF.net email is sponsored by: ApacheCon, November 18-21 in
> Las Vegas (supported by COMDEX), the only Apache event to be
> fully supported by the ASF. http://www.apachecon.com
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> drjava-hackers mailing list
> drj...@li...
> https://lists.sourceforge.net/lists/listinfo/drjava-hackers

Re: [DrJava] BeanShell

[Charles R. <cr...@ri...>]

   I've been looking at BeanShell this weekend to see if it would be a 
good replacement for DynamicJava.  Although there are a lot of nice 
features (like the import thing Peter mentioned), there still appears to 
be a huge problem:  you cannot define classes in the interpreter using 
Java (as far as I can tell).

   BeanShell provides support for "scripted objects" and even 
implementing a form of anonymous inner classes, but these do not use 
real Java syntax.  For example, to create an ActionListener, you would say:

buttonHandler = new ActionListener() {
     actionPerformed( event ) {
         print(event);
     }
};

   Note that typing "public void actionPerformed(ActionEvent event)" 
gives you a syntax error.  Being able to define classes and implement 
interfaces is a pretty big selling point for us, and we don't want to 
have to teach it in another language/style.  While the Strict Java mode 
appears to be ideal for us for statements and expressions, I think 
switching over to BeanShell would still be a huge step backwards if we 
had to give up dynamic class definitions.

   Of course, DynamicJava has it's own (fairly large) set of quirks and 
missing features, but I think it might be good to stick with it for now. 
  If BeanShell ends up adding support for classes in their Strict Java 
mode, then I'm in favor of switching (especially since BeanShell is a 
significantly more active project).

Charlie


ps--  If I'm mistaken and there is a way to do it, please let me know!


Peter Centgraf wrote:
> I just took another look at BeanShell, a java-like scripting environment 
> very similar to DynamicJava.  The website is here:
> 
> <http://www.beanshell.org/>
> 
> BeanShell has recently added a few features which would be of interest 
> to us for DrJava.  In particular, there is a new "Strict Java" mode, 
> which forces all variable declarations to be typed and all script 
> statements to have Java-legal syntax.  If I remember correctly, this 
> feature has already been requested for consistency reasons for teaching 
> in DrJava.  In normal mode, BeanShell will use DJ-style loose typing, as 
> well as automatic boxing and unboxing of primitives and an enhanced 
> print (i.e. System.out) mechanism.
> 
> Another feature that would be handy for newbies is a "global import" 
> statement: "import *" which maps out the entire classpath.  Ambiguities 
> in naming caused by the global import will be reported at runtime and 
> can be corrected with (an) additional import statement(s).  This is 
> coupled with a "which" command that prints the exact filesystem location 
> of any known Java identifier.  Considering the amount of difficulty that 
> new students have in understanding the classpath rules, this could be 
> extremely helpful.
> 
> BeanShell already ships with a Swing-based console which integrates via 
> I/O Streams or a custom interface, complete with history completion.  We 
> could also use a lower level of integration with the engine if we chose, 
> a la DynamicJava.  Everything is LGPL, so we'd have full access to the 
> code and it would be compatible with our license.
> 
> The last advantage would be consistency with other similar tools.  The 
> Emacs JDE already integrates with BeanShell, and Sun is planning to use 
> it in a future version of Forte and the NetBeans IDE.  As far as I can 
> tell, DynamicJava is a strict subset of BeanShell, so there's little 
> reason to hold out with an unpopular technology.
> 
> Obviously this would take a significant amount of work, but I think it 
> would be a worthwhile venture.  What opinions are there from the other 
> developers?
> 
> -- 
> Peter
> 
> 
> 
> -------------------------------------------------------
> This SF.net email is sponsored by: ApacheCon, November 18-21 in
> Las Vegas (supported by COMDEX), the only Apache event to be
> fully supported by the ASF. http://www.apachecon.com
> _______________________________________________
> drjava-hackers mailing list
> drj...@li...
> https://lists.sourceforge.net/lists/listinfo/drjava-hackers