Re: How-to evaluate Java-snippets in org-mode/org-babel?

[Torsten Wagner <torsten.wagner@gmail.com>]

Hi Eric,

> You probably don't want to pass the body of a code block to a lisp
> function as quoting will become a nightmare, however passing the name to
> a lisp block may be reasonable.
>
> I would suggest that rather than implementing this behavior in a code
> block you take a look at starting a ob-java.el file.  A partial
> implementation (e.g., only external evaluation, no session evaluation)
> would be a useful contribution, and given the many helper functions and
> examples present in the other ob-* files this would most likely be
> easier than a custom lisp-block implementation.

o.k. the first round of evaluations is over and it worked out o.k. 
However, there was still rather much handwork to do.
I tried to get a ob-java.el file together using the template and mainly 
by looking at ob-c.el which I guess comes close what would have to be 
done for java.
However, my lisp-skills (which are close to zero) are not enough to get 
it working. The main problem was that ob-c.el is working for both C and 
C++ and all this if then else troubles me a bit.

Basically, I want only tangle the actual code block into a temp file. 
Well temp is not really right, since java demand its file structure and 
file naming. Finally execute it externally by your proposed code

javac -cp . mypackage/myclass.java
java -cp . mypackage.myclass

and return the results

Hmm maybe better to give a real world example (stripped down to make it 
shorter)
I use now the following way
/-----------------------------------------------/
#+BABEL: :mkdirp t

* Coursework 1
** StudentID1
#+BEGIN_SRC java
   package foo;
   public class Bar
   {
           private double ans = 0
           public void set(double d){
                   ans = d;
           }
           public void print(){
                   System.out.println(ans);
           }
           public static void main(String[] argv){
                   Bar c = new Bar();
                   c.set(100);
                   c.print();
           }
   }
#+end_src

** StudentID2
#+BEGIN_SRC java
   package foo;
   public class Bar
   {
           private double x = 0
           public void set(double in){
                   x = in;
           }
           public void print(){
                   System.out.println(x);
           }
           public static void main(String[] argv){
                   Bar myclass = new Bar();
                   myclass.set(100);
                   myclass.print();
           }
   }
#+end_src

** Result
#+srcname: result
#+begin_src sh :results output
javac -cp . foo/Bar.java
java -cp . foo.Bar
#+end_src

/----------------------------------------------------/


For now I only added the tangle command to a single code block and 
created the file via C-c C-v t.

#+BEGIN_SRC java tangle: foo/Bar.java

Then I rushed down to a shell block  "result" which executed the the 
above commands. I checked the results and started to remove the tangle 
object from one block and added it to the next block. Kind of tiring if 
you have several dozen of blocks.
Guess you can see from the above example the trouble of having several 
dozen of them and then tangeling them one by one and execute the result 
block ;)

I tried to make it more easy by giving the shell block a name and call 
it under each java code block. This would save me the time going up and 
down in my file.

#+call: result()

However, I noticed that the result update was always done at the first 
appearances of the call , like under the first java code block but not 
at the desired code block?!
if you fold all together it would look like

/-----------------------------------------------/
#+BABEL: :mkdirp t

* Coursework 1
** StudentID1
#+BEGIN_SRC java
#+call: result()

#+results: result
: 100.0

** StudentID2
#+BEGIN_SRC java :tangle foo/Bar.java
#+call: result()

** Result
#+srcname: result
/-----------------------------------------------/

Calling the second call function updates the result on the first!

Anyhow, I guess having it working with a ob-java.el minimal system would 
be the most easiest. Simply type C-c C-c and it would be done.

Would be very glad if you could help me to get this somehow working.

Totti