Ok I’ve discussed with Guillaume Laforge from Groovy fame and here are more
details:
* In our code we capture the output of the script and use it to display the
rendered page so any println located directly in the script will work.
* However for a println in a Class, Groovy call System.out.println(…) - which
is why it goes in the xwiki logs - and we would need to capture that in a
thread safe way to redirect it to the page rendering this is a bit more
involved:
** Use System.set(PrintStream) with a custom PrintStream that would use for
example a threadlocal variable to direct the content to our page being rendered
** Use Groovy’s runtime metaprogramming feature, for example:
PrintStream.metaClass.println = { String s -> ...handle thread safety here.. }.
** Use Groovy’s compile-time metaprogramming feature and implement a Groovy AST
Transformation to transform all println calls into something else. For example
by adding a binding to the ScriptContext and using that binding instead of
println. This requires using a CompilationCustomizer (we already do that in
XWiki btw) which returns an ASTTransformationCustomizer to do the work.
Thanks
-Vincent
On 19 Dec 2014 at 00:10:18, Bryn Jeffries
(bryn.jeffr...@sydney.edu.au(mailto:bryn.jeffr...@sydney.edu.au)) wrote:
> Vincent Massol said:
> > Ok I think I know...
> > Actually the message is printed in the console.
> > You see something in the page only if you print in the global scope because
> > this is what gets returned by script evaluation. Calling “println” in a
> > class
> > doesn’t return anything in the evaluation and thus you don’t see anything.
> > That’s why the examples at
> > http://extensions.xwiki.org/xwiki/bin/view/Extension/Groovy+Macro work.
> >
>
> Right, makes sense. So looks like the best fix is to return the string and
> print it from global (script) scope. This works:
>
> {{groovy}}
> class Callee {
> def hello() {
> return "hello, world"
> }
> }
> c = new Callee()
> println c.hello()
> {{/groovy}}
>
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